Overview of Pressure Sensor Cables

A pressure sensor cable is a critical element in any pressure-sensing system. Unassumingly, it carries the pressure data from the sensor to the monitoring equipment, adapting to its environment while overcoming physical constraints. Some primary features of these cables include:

1. Conductors:

Typically made of copper or tinned copper wires, these conductors excel in electrical conductivity and corrosion resistance, ensuring an efficient transmission of signals.

2. Insulation:

Encasing the conductors, insulators provide electrical separation and protection and are often constructed from PVC, TPE, or Teflon to deliver excellent electrical, thermal, and chemical resistance.

3. Shielding:

Incorporated to decrease electromagnetic interference (EMI) and radio frequency interference (RFI), shielding can be fashioned from copper braid or aluminum foil.

4. Jacket:

The outer covering of the cable offers mechanical and environmental protection. PVC, TPE, and Teflon are popular choices due to their flexibility, temperature resistance, and chemical resistance.

Importance of Pressure Sensor Cables in Various Applications

Pressure sensor cables are instrumental in conveying precise pressure data from sensors to control systems or monitoring devices, and their appropriate selection is crucial to ensuring accuracy and efficiency. Some compelling examples of their applications include:

1. HVAC Systems:

In these systems, pressure sensor cables are vital in measuring and regulating parameters like refrigerant pressure, air pressure, and filter conditions. Selecting the right cable enables accurate and reliable data transmission, which translates to energy efficiency and peak system performance.

2. Hydraulic Systems:

Relying on these cables, hydraulic systems can closely monitor pressure data from pumps, valves, and actuators. Given the high-pressure environments and demanding conditions, robust cables with superior electrical properties are critical to maintaining system efficacy, reliability, and safety.

3. High-Pressure Gas Storage:

In this context, pressure sensor cables are key to safeguarding the storage and transportation of gases like natural gas or hydrogen. Accurate pressure measurements are paramount in preventing over-pressurization, leaks or catastrophic failures. Consequently, these cables require high burst pressure ratings and resistance to harsh chemicals and extreme conditions.

Types of Pressure Sensor Cables

Pressure sensor cables form the backbone of countless sensing systems, ensuring precise communication between pressure sensors and monitoring devices. The right cable type is crucial for achieving peak performance, and so, we must explore the distinct characteristics of each option:

1. General Purpose Pressure Sensor Cables:

These cables cater to a wide array of applications, providing the essential features for reliable pressure data transmission. With a typical conductor construction of copper or tinned copper wires, general-purpose cables offer excellent electrical conductivity and corrosion resistance. They are well-suited for industrial automation, HVAC systems, and fluid power systems.

2. High-Temperature Pressure Sensor Cables:

When pressure sensing systems are exposed to extreme temperatures, the high-temperature pressure sensor cables come to the rescue.

Superior materials such as PTFE (Teflon) insulation, silicone jacketing, or glass fiber braiding provide heat resistance up to 260°C (500°F). These cables are indispensable for applications involving exhaust gas pressure monitoring in automotive or aerospace sectors, or processes in the petrochemical industry.

3. Submersible Pressure Sensor Cables:

Waterproof and resistant to chemicals, corrosion, and abrasion, submersible pressure sensor cables go above and beyond to deliver reliable performance in underwater environments.

Designed to withstand submersion depths up to 500 meters (1640 feet), these cables are ideal for underwater monitoring systems, submersible pumps, and even oceanographic research.

They may feature polyurethane or PVC jackets for added protection against the harsh marine conditions.

Choosing the right materials for cables is essential to ensure peak performance in specific applications. In doing so, we’ll examine the unique characteristics of each material, while providing helpful knowledge and relevant content.

Material Choices for Pressure Sensor Cables

Three key materials set the standard for pressure sensor cables: Polyvinyl Chloride (PVC), Polyurethane (PUR), and Polytetrafluoroethylene (PTFE). Each material presents its own advantages and challenges. In order to select the most suitable cable for your application, it’s crucial to understand how they differ.

1. Polyvinyl Chloride (PVC) Cables:

PVC is popular due to its low cost, high flame resistance, and reasonable electrical properties.

However, there are downsides, such as degradation under sunlight, lower chemical resistance, and reduced performance at high temperatures (typically up to 85°C/185°F). PVC cables are ideal for general-purpose applications like HVAC systems, indoor installations, and automation equipment.

2. Polyurethane (PUR) Cables:

PUR rises above PVC in terms of durability, abrasion resistance, and flexibility.

With added resistance to oil, weather, and exceptional low-temperature performance (down to -40°C / -40°F), PUR cables shine under harsh conditions. This makes them the go-to choice for heavy-duty industrial applications, construction sites, and outdoor installations.

3. Polytetrafluoroethylene (PTFE) Cables:

PTFE, or Teflon, is hailed for its exceptional resistance to chemicals, high temperatures, and extreme environments.

Capable of withstanding temperatures up to 260°C (500°F), PTFE cables are often chosen for use in the aerospace, petrochemical, and automotive industries. The only downside to PTFE is its higher cost, which may not be justified in standard applications.

4. Which is good for Seawater?

PVC is a more cost-effective option, its susceptibility to degradation in a seawater environment makes it less ideal for this application. PTFE, though more expensive, is likely to provide a more durable and reliable solution due to its superior chemical resistance and mechanical properties.

PUR could be a suitable choice for a seawater application, offering a balance between cost, chemical resistance, and mechanical durability. However, for long-term exposure to harsh seawater conditions, PTFE might still be the more reliable choice due to its superior chemical resistance. As always, it’s critical to consider the specific requirements and constraints of your application when making your choice.

In a seawater environment, PTFE’s excellent chemical resistance makes it an ideal choice. It can withstand the harsh conditions without degrading, ensuring the longevity and reliability of your level transmitter.

Therefore, if longevity and reliability in harsh conditions are a priority, then PTFE would be the better choice.

Below is a comparison table summarizing key material properties:

Industry	Cable Requirements	Material	Temperature Range	Chemical Resistance	Mechanical Strength	Environmental Factors	For water	For oil
Medical	Biocompatible, sterilizable, low noise, good signal transmission	PTFE(Teflon), Silicone	Varies depending on application	Good	Good	Cleanliness, flexibility	Excellent	Excellent
HVAC	Wide temperature range, moisture resistance, chemical exposure	PVC, TPE	-40°C to +105°C	Moderate	Moderate	Moisture, UV resistance	Fair	Fair
Oil/Gas	Extreme temperatures, high pressures, harsh chemicals	PTFE(Teflon), ETFE	-200°C to +200°C	Excellent	High	High pressure, temperature	Excellent	Excellent
Deep Well Level Measurement	High pressures, moisture resistance, chemical exposure	PE, PUR	-40°C to +80°C	Good	Good	High pressure, moisture	Excellent	Excellent

Hope above analysis should equip you with the vital information needed to choose the material for your pressure sensor cable application.

Selecting the Right Pressure Sensor Cable

We must consider several aspects to choose the most appropriate pressure sensor cable, including application requirements, environmental factors, cable length, flexibility, and consulting with manufacturers. Let’s examine these factors step by step, providing relevant content and helpful knowledge to support and guide your decision-making process.

1. Application requirements:

Assess the cable’s purpose, voltage, and current capacity needed. Consider load cell or strain gauge types, measurement range, accuracy, and temperature compensation requirements. This analysis will ensure that selected cables meet the application’s demands.

 2. Environmental factors:

Evaluate the cable’s exposure to environmental conditions such as water, oil, chemicals, temperature fluctuations, and UV radiation. As discussed in our previous blog post on material choices for pressure sensor cables, these factors influence the cable material selection.

3. Cable length and flexibility requirements:

Determine the necessary cable length and evaluate if flexibility is critical, especially in confined spaces. Extended lengths may influence signal quality, so select cables with appropriate shielding, insulation, and conductor materials.

4. Consulting with manufacturers for custom solutions:

Collaborating with cable manufacturers could yield tailored solutions, meeting specific requirements or unique conditions. These solutions may involve custom cable designs, additional shielding, or specialized terminations.

Here is a summary of decision-making factors is found in the table below:

Factors	Considerations	Examples
Application Requirements	Voltage,	Load cells,
	Current capacity,	Strain gauges,
	Sensor type,	Temperature compensation
	Measurement range,
	Accuracy
Environmental Factors	Exposure to water or oil,	PVC, PUR, PTFE cables
	Exposure to chemicals or others media,
	Temperature fluctuations,
	UV radiation
Cable Length & Flexibility	Cable length,	Shielding,
	Signal quality,	Insulation,
	Space constraints	Conductor materials
Consultation with Manufacturers	Custom cable designs,	Tailored solutions for unique requirements
	Additional shielding,
	Specialized terminations

At last, taking into account these crucial factors will enable you to select the right pressure sensor cable confidently, ensuring optimal performance and reliability in your required application.

Cable Connectors and Termination Options

Let’s start with an understanding of the three most common connector types used in pressure sensor cables:

1. Circular connectors:

These types of connectors are widely used in various industries, particularly in harsh environments, as they offer excellent protection against environmental factors such as water and dust. Circular connectors often come in a variety of pin configurations and are generally built with durable materials such as brass or stainless steel, while the insulating body is usually made of plastic or rubber.

Notable circular connector series include the M12, M8, and 7/8″ connectors.

2. Terminal block connectors:

Terminal block connectors are an ideal choice for applications where ease of installation is a priority.

They are typically panel-mounted and consist of a series of terminal points, allowing for multiple sensors to be connected to a single terminal block. These connectors offer secure connections as wires are clamped down using screws or spring-loaded mechanisms, ensuring a dependable bond between the cable and the connector.

3. Direct wire:

In some cases, pressure sensors may not require any specific connector type and can be directly wired to the sensing device. This option is cost-effective and provides maximum design flexibility. However, direct wiring poses challenges when it comes to the maintenance and replacement of the pressure sensor.

Now, let’s explore the key mechanical and environmental considerations when selecting connectors for pressure sensor cables:

1. Operating temperature:

Depending on the application, pressure sensor cables may be exposed to extreme high and low temperatures. Therefore, ensuring that the chosen connector material can withstand these temperatures without experiencing degradation or failure is essential.

2. Ingress protection (IP) rating:

Connectors in harsh environments should have a high IP rating to ensure optimal protection against dust and water intrusion. Standard IP ratings include IP67, which offers protection against dust and temporary immersion, and IP68, which protects against dust and continuous immersion.

3. Chemical resistance:

In certain industrial environments, connectors may come into contact with corrosive chemicals. Selecting materials that can resist the chemicals’ damaging effects is crucial in these cases.

4. Vibration and shock resistance:

Since pressure sensor cables are often employed in dynamic applications, connectors should be designed to withstand vibrations and mechanical shocks without compromising their performance or reliability.

As promised, here’s a summary table that includes relevant data, numbers, and models for the cable connectors and termination options we’ve discussed so far:

Factor	Importance	Examples / Data
Operating Environment	Must withstand environmental conditions such as water, chemicals, dust, or humidity	IP ratings (IP67, IP68)
Temperature Range	Must be compatible with the application's temperature range	-40°C to +125°C
Chemical Compatibility	Must be resistant to chemicals it may come in contact with	Resistance to acids, bases, solvents
Mechanical Stress	Must withstand tension, compression, bending, or abrasion	Tensile strength, flexibility
Cable Length	Should be appropriate for the application, considering signal attenuation and installation	1m, 5m, 10m, etc.
Shielding Requirements	Reduce EMI if necessary	Shielded or unshielded cables
Connector Types	Must be compatible with the pressure sensor and output device	M12, M8, DIN, et

Cable Shielding and Grounding

Significance of shielding:

First, let’s begin by examining the importance of shielding in preventing electromagnetic interference (EMI): Pressure sensors can be sensitive to electromagnetic noise generated by nearby electrical devices, power lines, or even radio frequency transmissions. EMI can cause inaccurate sensor readings, leading to operational difficulties and unreliable performance. Shielding effectively minimizes EMI and ensures precise and reliable data from pressure sensors.

Techniques for improving noise immunity

Now, let’s discuss some techniques for improving noise immunity:

1. Twisted pair cables:

Using twisted pair cables can significantly reduce the impact of EMI. The twisting of the conductors equalizes the exposure to external electromagnetic fields, effectively canceling out noise and increasing noise immunity.

2. Shielding materials:

Implementing proper shielding materials is essential in minimizing EMI. Common shielding materials include copper, aluminum, and steel. The choice of shielding material depends on several factors, including the frequency range of the electromagnetic noise and overall cost constraints.

3. Shielding effectiveness:

Achieving optimal shielding effectiveness requires a balance between the conductivity of the shielding material, its thickness, and the frequency of the electromagnetic noise. Higher conductivity materials generally provide better shielding effectiveness.

Grounding best practices for pressure sensor cables

Finally, let’s explore grounding best practices for pressure sensor cables:

1. Single-point grounding:

Providing a single-point ground for the shielding material is essential to minimize ground loops and reduce noise. This ensures any EMI absorbed by the shield is properly directed to ground.

2. Proper grounding techniques:

When grounding the shielding, it is crucial to ensure a low impedance connection to ground. This can be achieved by using short and wide grounding straps or large surface area grounding pads to provide minimal resistance.

3. Regular inspection and maintenance:

Regularly inspect and maintain the grounding connections for pressure sensor cables to ensure proper shielding effectiveness and prevent potential issues due to corrosion, loose connections, or damage to the shielding.

Continue: Pressure Sensor Cable part 2/2

O-Ring Introduction

An O-ring is an essential component in pressure sensor design and manufacturing, playing a critical role in ensuring proper sealing and reliable performance. An O-ring is a loop of elastomeric material, typically shaped like a torus (a donut), and is used to create a leak-proof seal between two or more parts of a mechanical system.

In pressure sensors, O-rings are a barrier to prevent the ingress of fluids, gases, or other environmental contaminants and maintain the sensor’s accuracy and stability.

The primary role of an O-ring in a pressure sensor is to provide a reliable seal between the sensing element and the housing or between the housing and the process connection. This seal helps protect the internal components from external factors such as moisture, dust, and chemicals, ensuring the sensor’s longevity and consistent performance in various environmental conditions.

O-rings are primarily used to prevent the loss of a fluid or gas during pressure measurement; meanwhile, O-rings can also be used as dust seals, drive belts or on rotating shafts. Most O-ring seals can be classified into one of the three arrangements shown below.

In the line of pressure measurement and control, O-rings are made from a variety of elastomeric materials, such as Nitrile, Viton, EPDM, silicone, and others, each with its own unique properties, advantages, and limitations. The choice of O-ring material is crucial, as it must be compatible with the specific application’s process media, temperature range, and pressure conditions. Factors such as chemical compatibility, temperature resistance, compression set resistance, and mechanical strength should be considered when selecting an appropriate O-ring material for a pressure sensor.

In addition to material selection, the proper sizing and installation of O-rings are essential for achieving an effective seal. O-ring dimensions, including inner diameter, cross-sectional diameter, and groove dimensions, must be carefully considered to ensure optimal sealing performance. Proper installation techniques are also critical to avoid damage to the O-ring or sensor components and maintain the seal’s integrity.

O-Ring Types & Features

Various types of O-rings are available in the market, mainly categorized based on their material composition. Here are some common O-ring materials and their key properties:

Nitrile (NBR):

• Operating temperature range: -40°C to 120°C | -40°F to 248°F
• Good resistance to petroleum-based oils and fuels
• Presently the most widely used elastomer in the seal industry
• It provides an exceptional balance of good mechanical properties, wear properties and chemical resistance
• Resistant to most mineral oils and greases
• Do not use with glycol-based brake fluids and strong acids
• Not suitable for highly polar solvents or strong acids
• Low temperature nitrile compound available with a minimum temperature of -54°C/65°F

Fluorocarbon (FKM or Viton):

• Operating temperature range: -20°C to 200°C | -15°F to 400°F
• Excellent resistance to high temperatures and chemicals
• Excellent resistance to higher temperatures, petroleum oils, and gasoline
• Wide range of chemical resistance
• Excellent ozone, weather, and aging resistance
• Poor compatibility with H2S over 2%, amines, acetone, hot water, and steam
• Poor low temperature characteristics
• Low temperature fluorocarbons are available with a minimum temperature of -40°C/-40°F
• Not recommended for low temperatures or exposure to ketones

Ethylene Propylene (EPDM):

• Operating temperature range: -50°C to 150°C | -65°F to 302°F
• Good resistance to weathering, ozone, and water-based chemicals
• Excellent resistance to ozone, hot water, steam, and aging
• Commonly used with brake fluids and refrigerants
• Poor resistance to petroleum fluids and mineral oils
• Not suitable for petroleum-based oils or fuels

Silicone (VMQ):

• Operating temperature range: -60°C to 225°C | -85°F to 450°F
• Excellent flexibility and resistance to extreme temperatures
• Excellent resistance to oxidation and ozone degradation
• Wide temperature range
• Most commonly used in static applications due to its poor tensile strength and wear resistance
• Popular for food and medical applications
• Not recommended for dynamic sealing applications or exposure to fuels

Polyurethane (PU,AU,EU):

• Good resistance to wear, extrusion, and tear
• Operating temperature range: -40°C to 90°C | -65°F to 220°F
• Thermoplastic elastomer with higher tensile strength, toughness, and wear resistance
• Good combination of hardness and elasticity
• Good low temperature flexibility
• Limited resistance to high temperatures and some chemicals
• Used in high pressure hydraulic systems where parts are subject to wear

Perfluoroelastomer (FFKM or Kalrez):

• Operating temperature range: -20°C to 327°C | +5°F to 590°F
• Exceptional resistance to chemicals and high temperatures
• High cost and not suitable for low-temperature applications
• Broadest chemical resistance of any elastomeric material
• High temperature compounds available up to 325°C/617°F
• Combines the sealing integrity of elastomers with chemical resistance approaching that of PTFE
• Not suitable with liquid sodium and potassium, fluorinated solvents, and refrigerants

O-Ring selection in view of sensing technology

The table below shows the common O-Ring materials used for various sensing technologies, along with model examples, material used, duration, temperature range, and their pros and cons. This information can help you choose the appropriate O-Ring material for your specific application based on the sensing technology employed. Keep in mind that the material compatibility with the sensing technology and the media being measured is crucial for the proper functioning of the pressure sensor.

Sensing Technology	O-Ring Material	Model Example	Material Used	Duration	Temperature Range	Pros	Cons
Capacitive Pressure Sensors	EPDM	EPDM-70	Ethylene Propylene	Long	-50°C to 150°C	Good water & steam resistance	Not for petroleum-based oils or fuels
Piezoresistive Pressure Sensors	NBR	NBR-70	Nitrile	Long	-40°C to 120°C	Good oil & fuel resistance, cost-effective	Not for polar solvents or strong acids
Optical Pressure Sensors	FKM	FKM-75	Fluorocarbon	Long	-20°C to 200°C	Excellent chemical resistance, high temp.	Not for low temperatures or ketones
Strain Gauge Pressure Sensors	PU	PU-90	Polyurethane	Long	-40°C to 90°C	Excellent abrasion resistance, good flexibility	Limited high temp. and chemical resistance
Resonant Pressure Sensors	FFKM	FFKM-80	Perfluoroelastomer	Long	-20°C to 327°C	Exceptional chemical & temperature resistance	High cost, not for low-temperature applications
Piezoelectric Pressure Sensors	VMQ	VMQ-60	Silicone	Long	-60°C to 225°C	Wide temperature range, low toxicity	Not for dynamic sealing or fuels

O-Ring selection based on industry applications

The table below shows the common O-Ring materials used in various industries, model examples, material used, duration, temperature range, and their pros and cons. This information can help you choose the appropriate O-Ring material for your specific application based on industry requirements.

Industry	O-Ring Material	Model Example	Material Used	Duration	Temperature Range	Pros	Cons
Automotive	NBR	NBR-70	Nitrile	Long	-40°C to 120°C	Good oil & fuel resistance, cost-effective	Not for polar solvents or strong acids
Oil & Gas	FKM	FKM-75	Fluorocarbon	Long	-20°C to 200°C	Excellent chemical resistance, high temp.	Not for low temperatures or ketones
Water Applications	EPDM	EPDM-70	Ethylene Propylene	Long	-50°C to 150°C	Good water & steam resistance	Not for petroleum-based oils or fuels
Aerospace	VMQ	VMQ-60	Silicone	Long	-60°C to 225°C	Wide temperature range, low toxicity	Not for dynamic sealing or fuels
Food & Beverage	VMQ	VMQ-FDA	Silicone	Long	-60°C to 225°C	FDA approved, low toxicity, wide temp. range	Not for dynamic sealing or fuels
Chemical Processing	FFKM	FFKM-80	Perfluoroelastomer	Long	-20°C to 327°C	Exceptional chemical & temperature resistance	High cost, not for low-temperature applications
Semiconductor	FFKM	FFKM-75	Perfluoroelastomer	Long	-20°C to 327°C	Exceptional chemical & temperature resistance	High cost, not for low-temperature applications
Hydraulics & Pneumatics	PU	PU-90	Polyurethane	Long	-40°C to 90°C	Excellent abrasion resistance, good flexibility	Limited high temp. and chemical resistance

Common O-Ring Failures

O-rings, often made of elastomeric materials, provide sealing between two mating components by applying a mechanical barrier to limit the movement of fluids or gases. In the context of pressure sensors, O-rings play a vital role in ensuring that the sensor can accurately measure and maintain pressure levels without leakage, to choose the best O-Ring for a pressure sensor, you must be, not only, familiar with the importance of O-rings in various applications, also know the common failures of O-Ring like extrusion, compression, chemical degradation etc.

Extrusion and Nibbling:

This occurs when high-pressure fluid or gas forces the O-ring material into the narrow clearance between mating components. It can lead to the O-ring losing its shape and subsequently failing to seal the system. In pressure sensors, extrusion can cause inaccurate readings or device malfunctions.

• Description: The seal develops ragged edges, generally on the low-pressure side, which appear tattered.
• Contributing Factors: Excessive clearances, excessive pressure, low modulus/hardness elastomer, excessive gland fill, irregular clearance gaps, sharp gland edges, improper sizing.
• Suggested Solutions: Decrease clearances, higher-modulus/hardness elastomer, proper gland design, use of polymer backup rings.

There are different methods to counter O-ring extrusion. One of these methods is to increase the durometer rating of the O-ring. However, as the durometer is increased, the O-ring can become less malleable. Another option would be the use of anti-extrusion devices. These are thin rings made of hard plastic materials such as PTFE, nylon, and PEEK. Once in place these rings will provide essentially zero clearance.

 

Compression set:

A compression set occurs when the O-ring loses its ability to return to its original shape after being subjected to continuous compression. It can be due to excessive heat or because of the material aging. Since pressure sensors depend on the O-ring’s sealing capabilities, a high compression set can cause inaccurate measurements, leakages, and overall device failure.

Description: The seal exhibits a flat-sided cross-section, the flat side corresponds to the mating seal surfaces.

Contributing Factors: Excessive compression, excessive temperature, incompletely cured elastomer, elastomer with high compression set, excessive volume swell in chemical.

Suggested Solutions: Low compression set elastomer, proper gland design for the specific elastomer, confirm material compatibility.

Fracturing and Cracking:

Fractures and cracks can develop within the O-ring due to various factors such as excessive cold or heat exposure, incorrect sizing, poor installation, or damage during installation. In pressure sensors, a compromised O-ring can lead to fluid leakage or device failure.

Let’s take poor installation, for example:

• Description: The seal or parts of the seal may exhibit small cuts, nicks, or gashes.
• Contributing Factors: Sharp edges on the glands or components, improper sizing of elastomer, low-modulus/hardness elastomer, elastomer surface contamination.
• Suggested Solutions: Remove all sharp edges. Proper gland design, proper elastomer sizing, higher-modulus/hardness elastomer.

Chemical degradation:

O-ring material can degrade due to exposure to corrosive chemicals, reducing the sealing effectiveness, swelling, or even disintegration of the O-ring. In pressure sensors, chemical degradation can contribute to leakages and inaccurate pressure measurements.

• Description: The seal may exhibit many signs of degradation including blisters, cracking, voids or discoloration. In some cases, the degradation is observable only by measurement of physical properties.
• Contributing Factors: Incompatibility with the chemical and/or thermal environment.
• Suggested Solutions: Selection of a more chemically resistant elastomer.

Abrasion:

O-rings can experience abrasion due to friction between mating surfaces, resulting in erosion of the elastomeric material. In pressure sensors, abrasion can lead to fluid leakage, inaccurate pressure readings, and potential device failure.

• Description: The seal or parts of the seal exhibit a flat surface parallel to the direction or motion. Loose particles and scrapes may be found on the seal surface.
• Contributing Factors: Rough sealing surfaces, excessive temperature, process environment containing abrasive particles, dynamic motion, poor elastomer surface finish.
• Suggested Solutions: Use recommended gland surface finishes, consider internally lubed elastomers, eliminate abrasive components.

How to prevent or mitigate the failures in pressure sensors

Material selection:

Choose an O-ring material that is compatible with the fluids, gases, and temperatures involved in the application. In pressure sensors, common materials include Nitrile, Viton, EPDM, and Silicone, offering different combinations of chemical resistance, thermal stability, and mechanical properties.

For details and comparison, you can check the below table of common O-ring technical data & key properties.

Type	Material	Temperature Range	Chemical Resistance	Abrasion Resistance	Cost	Highlight Features	Suitable Industries	Limitations
Nitrile (NBR)	Acrylonitrile Butadiene	-40°C to +120°C	Good	Good	Low	Good chemical and oil resistance	Automotive, industrial, hydraulics	Poor resistance to ozone and UV light
Silicone (VMQ)	Silicone elastomer	-60°C to +225°C	Fair	Fair	High	Excellent temperature resistance	Electronics, aerospace, automotive	Poor tensile strength, tear resistance
Fluorocarbon (FKM/Viton)	Fluorinated hydrocarbon	-20°C to +200°C	Excellent	Good	High	Excellent chemical and heat resistance	Automotive, aerospace, chemical	Not suitable for low temperatures
Ethylene Propylene (EPDM)	Ethylene Propylene diene monomer	-55°C to +150°C	Good	Fair	Low	Excellent ozone, UV, and weather resistance	Automotive, water systems, HVAC	Poor resistance to oils and fuels
Neoprene (CR)	Polychloroprene	-40°C to +120°C	Good	Good	Good	Good resistance to ozone, UV, and weather	Refrigeration, automotive, marine	Moderate chemical and temperature resistance
Polyurethane (AU/EU)	Urethane elastomer	-30°C to +100°C	Fair	Excellent	Medium	Excellent abrasion and tear resistance	Hydraulic systems, automotive	Poor resistance to high temperatures
Perfluoroelastomer (FFKM)	Fully fluorinated elastomer	-20°C to +330°C	Exceptional	Good	Very High	Exceptional chemical and heat resistance	Semiconductor, chemical, aerospace	High cost, limited low-temperature performance
Hydrogenated Nitrile (HNBR)	Hydrogenated Acrylonitrile Butadiene	-40°C to +150°C	Good	Fair	Medium	Improved ozone, UV, and chemical resistance compared to NBR	Automotive, oil and gas, industrial	Limited resistance to polar solvents, strong acids

Size and design:

Proper sizing and tolerances are crucial for O-ring performance. Follow established guidelines and standards for O-ring size selection, groove design, and gland dimensions, such as ISO 3601, AS568, and JIS standards.

In the industries, ISO 3601, AS568, and JIS standards are international standards that provide essential information for selecting and designing O-rings and their corresponding grooves. They cover important aspects such as dimensions, tolerances, material specifications, and quality assurance criteria. Here are some useful knowledge points about these standards in relation to O-rings:

Standard	Description	Dimensions	Tolerances	Material Specifications
ISO 3601	Guidelines for O-ring sizes and quality acceptance criteria provided by the International Organization for Standardization (ISO).	Specifies a range of O-ring sizes, identified by an O-ring identification number (ID). Covers inside diameter (ID), cross-section diameter (CS), and tolerances.	Establishes tolerances on O-ring dimensions and surface irregularities.	Does not specify material types; focuses only on dimensions and tolerances.
AS568	Standardized system for O-rings developed by the Society of Automotive Engineers (SAE), specifically for Aerospace applications but widely applicable in other industries as well.	Provides a list of 379 standard sizes, known as dash numbers, for O-rings. Covers inside diameters (IDs) and cross-sectional diameters (CSs).	Specifies tolerances for both ID and CS dimensions.	Does not specify material types; focuses only on dimensions and tolerances.
JIS B 2401	Japanese Industrial Standards (JIS) for O-ring sizes and tolerances, focused on general industrial applications and developed by the Japanese Standards Association (JSA).	Establishes dimensions (ID and CS) and tolerances for a range of standard O-ring sizes.	Specifies tolerances for O-ring dimensions, ensuring interchangeability and compatibility in various applications.	Does not specify material types; focuses only on dimensions and tolerances.

Installation:

Ensure correct O-ring installation and lubrication during assembly to minimize damage, distortion, or stress on the O-ring. In pressure sensors, you need to pay close attention to the mating surfaces, clean and smooth sealing areas, and firmly secure components together.

• Choose the appropriate O-ring size based on the specific application and the applicable standards (ISO 3601, AS568, or JIS B 2401).
• Select the suitable O-ring material compatible with the operating temperature, pressure, and chemical environment.
• Inspect the O-ring for any visible defects such as cracks, cuts, or abrasions before installation.
• Check the dimensions of the O-ring to ensure it meets the specified tolerances in terms of ID and CS dimensions.
• Ensure the components’ mating surfaces are clean and free of any debris, burrs, or sharp edges that could damage the O-ring during installation.

When installing, do not roll or stretch the O-ring excessively to prevent damage or distortion.

Use tools such as O-ring installation cones, picks, or sleeves to properly place the O-ring in its groove without causing damage or pinching. Make sure the O-ring is seated correctly and without twists or kinks in the groove.

During assembly, ensure a slow and steady pace to minimize stress or distortion of the O-ring.

Lubrication:

Use a suitable lubricant compatible with the O-ring material and the application’s environment. Lubricants can help prevent damage, reduce friction, and ease assembly.

Apply a thin, uniform layer of lubricant on the O-ring’s surfaces and the components’ grooves and mating surfaces.

Avoid using excess lubricant as it can attract dirt or debris, causing contaminations and potential damage to the O-ring.

Visually inspect the O-ring after installation to ensure it is seated properly and free of damage or distortion.

Perform a pressure or vacuum test, if applicable, to verify the O-ring’s sealing effectiveness and ensure there are no leaks.

Wrap up

To select the appropriate O-Ring, consider factors such as industry and sensing technology. For example, in the A/C and refrigerator industry, O-Rings should be compatible with refrigerant gases, withstand low temperatures, and have good chemical resistance. When choosing an O-Ring for a specific sensing technology, it is necessary to consider the operating conditions, such as temperature, pressure, and chemical exposure, to ensure optimal performance.

Understanding the key technical data for O-Rings is essential when selecting the right one for your pressure sensor. Pay attention to dimensions, tolerances, material properties, temperature range, and compatibility with the media. Make sure to consider potential risks and limitations, such as material incompatibility, improper sizing, installation damage, shelf life, temperature and pressure fluctuations, lubrication, extrusion, compression set, and the need for regular maintenance and inspection.

Remember to store O-Rings properly, use compatible lubricants, and inspect them regularly to ensure optimal performance and longevity. By considering these factors, you can make informed decisions when choosing and using O-Rings in your pressure sensor applications, resulting in reliable and efficient operation.

At last, understanding common O-ring failures for pressure sensors is crucial for achieving reliable and accurate pressure measurements. Regular inspection and maintenance, appropriate material selection, and proper installation techniques can all contribute to the optimal performance and longevity of the O-ring seals.

Material selection is crucial for pressure sensor production because the chosen materials can significantly impact the sensor’s performance, durability, and resistance to various environmental factors.

Different materials have varying properties such as corrosion resistance, strength, and stiffness, which makes them suitable for specific operating conditions.

The selection of materials should consider the type of sensing element used in the pressure sensor. For example, some pressure sensors use a strain gauge to measure pressure. In this case, the material used to make the strain gauge must be durable and resist mechanical fatigue, so it doesn’t deform over time from repeated loads. Other pressure sensors may use a piezoelectric or capacitive element to sense pressure, where material properties such as dielectric constant, resistivity, and thermal expansion coefficients become critical.

Today, I’d like to provide insights into choosing the proper and qualified materials for pressure sensor sensing elements, PCB, Filled Fluid, O-Rings, Cable and Wires, Housing and Wetted parts as below.

Material of Sensing element

There are several types of materials commonly used for sensing elements, including:

Silicon:

Silicon is the most common material used for pressure sensor sensing elements. It is used in piezoresistive and capacitive pressure sensors. Silicon has excellent mechanical properties, high sensitivity, and good long-term stability. However, silicon is sensitive to temperature changes, and its performance can degrade under harsh environmental conditions.

Stainless steel:

Stainless steel is a popular material for sensing elements in harsh environments due to its excellent corrosion resistance, durability, and strength. It is commonly used in strain gauge pressure sensors, where the sensing element is bonded to a metal diaphragm.

Ceramic:

Ceramic sensing elements are used in capacitive and thick-film pressure sensors. They offer good chemical resistance, and temperature stability, and are suitable for harsh environments. However, ceramics can be brittle and may not be ideal for high shock or vibration applications.

Metal foil strain gauges:

Metal foil strain gauges are often used in bonded strain gauge pressure sensors. They provide good stability and can withstand high pressures, but their sensitivity is lower than silicon-based sensors.

Material	Pros	Cons
Silicon	- High sensitivity	- Sensitive to temperature changes
	- Good long-term stability	- Not ideal for harsh environments
	- Suitable for small pressure ranges
Stainless Steel	- Excellent corrosion resistance	- Lower sensitivity compared to silicon
	- High durability and strength	- Heavier and bulkier
	- Suitable for high pressure ranges
Ceramic	- Good chemical resistance	- Brittle and less suitable for high shock
	- Temperature stability	or vibration applications
	- Suitable for harsh environments	- Lower sensitivity compared to silicon
Metal Foil Strain Gauges	- Good stability	- Lower sensitivity compared to silicon
	- Can withstand high pressures	- Less suitable for small pressure ranges

When selecting the material for a pressure sensor sensing element, you need to consider factors such as the pressure range, sensitivity requirements, operating temperature, and environmental conditions (e.g., corrosion, shock, vibration). Each material has its advantages and drawbacks, so the choice will depend on the specific requirements of your application.

Material of pcb

It’s essential to pay attention to the choice of material for the PCB (printed circuit board) when designing a pressure sensor, as it can impact the performance, reliability, and overall quality of the sensor. Here’s a comparison of some common PCB materials:

When choosing a PCB material, consider factors such as your pressure sensor’s operating temperature, frequency, and mechanical stress requirements.

For example, if your sensor is used in high-temperature environments or requires high-frequency performance, you might choose a material like polyimide or PTFE. However, if cost is a significant concern and the sensor operates within standard temperature ranges, FR-4 may be a suitable option. Always weigh the pros and cons of each material based on the specific requirements of your pressure sensor application.

Material	Thermal Conductivity (W/m·K)	Dielectric Constant	Loss Tangent	Tg (Glass Transition Temperature) (°C)	Cost (Relative)
FR-4 (Standard)	0.8 - 1.5	4.3 - 4.8	0.02 - 0.025	130 - 170	Low
Polyimide	0.5 - 0.6	3.4 - 4.4	0.002 - 0.02	250 - 260	Medium
PTFE (Teflon)	0.2 - 0.3	2.1 - 3.0	0.0009 - 0.0015	NA	High
Rogers	0.8 - 1.5	3.0 - 10.2	0.0013 - 0.0037	280 - 390	High

Remember that the specific values can vary depending on the manufacturer and grade of the material. When selecting a PCB material for your pressure sensor, consider factors like thermal conductivity, dielectric constant, loss tangent, and the glass transition temperature (Tg) in addition to the cost. Choose a material that best suits the requirements of your specific application.

Material of filled fluid

Fluid-filled pressure sensors are often used when dealing with high levels of vibration, shock, or when temperature compensation is necessary. They can also provide better long-term stability and help reduce the effects of mechanical stress. Here is a table comparing common fluid materials used in fluid-filled pressure sensors:

Fluid Material	Viscosity (cP)	Temperature Range (°C)	Compatibility with Materials	Pros	Cons
Silicone Oil	10 - 100	-50 to 200	Most metals, elastomers, and plastics	Wide temperature range, good chemical resistance, low toxicity	Can become contaminated or leak
Mineral Oil	10 - 100	-10 to 150	Most metals, elastomers, and plastics	Low cost, good lubrication, wide availability	Less chemically stable than silicone oil, narrower temperature range
Inert Gases (e.g., Nitrogen)	Varies	-200 to 200	Most metals, elastomers, and plastics	Non-reactive, can handle extreme temperatures, no risk of leaks	Requires a sealed system, may cause measurement inaccuracies if pressure changes
Fluorocarbon-based Oils	100 - 1000	-40 to 280	Most metals, some elastomers and plastics	Excellent chemical resistance, wide temperature range	Higher cost, limited material compatibility
Glycol-based fluids	30 - 200	-40 to 120	Most metals, elastomers, and plastics	Good lubrication, low cost, biodegradable	Limited temperature range, can absorb moisture

Material of O-ring

O-rings are used in pressure sensors to create a tight seal between components and prevent the ingress of contaminants, moisture, or other substances that could compromise the sensor’s performance. O-rings are typically required in applications where the sensor is exposed to harsh environments, high pressures, or corrosive media.

Here’s a table comparing various O-ring materials, their pros, and cons:

Type	Material	Temperature Range	Highlight Features	Suitable Industries	Limitations
Nitrile (NBR)	Acrylonitrile Butadiene	-40°C to +120°C	Good chemical and oil resistance	Automotive, industrial, hydraulics	Poor resistance to ozone and UV light
Silicone (VMQ)	Silicone elastomer	-60°C to +225°C	Excellent temperature resistance	Electronics, aerospace, automotive	Poor tensile strength, tear resistance
Fluorocarbon (FKM/Viton)	Fluorinated hydrocarbon	-20°C to +200°C	Excellent chemical and heat resistance	Automotive, aerospace, chemical	Not suitable for low temperatures
Ethylene Propylene (EPDM)	Ethylene Propylene diene monomer	-55°C to +150°C	Excellent ozone, UV, and weather resistance	Automotive, water systems, HVAC	Poor resistance to oils and fuels
Neoprene (CR)	Polychloroprene	-40°C to +120°C	Good resistance to ozone, UV, and weather	Refrigeration, automotive, marine	Moderate chemical and temperature resistance
Polyurethane (AU/EU)	Urethane elastomer	-30°C to +100°C	Excellent abrasion and tear resistance	Hydraulic systems, automotive	Poor resistance to high temperatures
Perfluoroelastomer (FFKM)	Fully fluorinated elastomer	-20°C to +330°C	Exceptional chemical and heat resistance	Semiconductor, chemical, aerospace	High cost, limited low-temperature performance
Hydrogenated Nitrile (HNBR)	Hydrogenated Acrylonitrile Butadiene	-40°C to +150°C	Improved ozone, UV, and chemical resistance compared to NBR	Automotive, oil and gas, industrial	Limited resistance to polar solvents, strong acids

Material of Cable and Wires

First, let’s clarify the difference between wires and cables in the context of pressure sensors:

• Wires: A wire is a single, flexible, cylindrical conductor that transmits electricity. It is typically made of a metal core (usually copper or aluminum) and an insulating material to cover and protect the core.
• Cables: A cable consists of multiple wires or conductors bundled together, usually with an insulating or protective outer layer. Cables can transmit electrical signals or power, and their construction allows for more complex connections and greater durability in various environments.

Click for more details about the pressure sensor cable

Now, let’s look at the materials used for wires and cables:

Type	Material	Pros	Cons	Limitations	Common Applications	Model Types/Examples
Wire	Copper	High electrical conductivity (5.96×10^7 S/m), good flexibility, solderable	Heavier, less resistant to corrosion than aluminum	Susceptible to corrosion in certain environments	Power transmission, data transmission, electronics	AWG, THHN, THWN
Wire	Aluminum	Lightweight, good electrical conductivity (3.77×10^7 S/m), cost-effective	Less flexible, less solderable, prone to oxidation	Oxidation, less flexible, difficult to solder	Power transmission, overhead lines, automotive	AA, AAAC, ACSR
Insulation (Wire/Cable)	PVC (Polyvinyl Chloride)	Economical, flexible, flame retardant, good insulating properties	Not ideal for high temperatures or extreme environments	Limited temperature range (-40°C to 105°C), not suitable for harsh environments	General-purpose wiring, automotive, building wiring	UL 1015, UL 1007
Insulation (Wire/Cable)	PTFE (Teflon)	Excellent chemical resistance, wide temperature range (-196°C to 260°C), flame retardant	Higher cost, stiffer than PVC	Higher cost, stiffer than other insulation materials	Harsh environments, aerospace, chemical processing	MIL-W-16878, Type E
Insulation (Wire/Cable)	Silicone	Good temperature range (-60°C to 180°C), flame retardant, flexible	Lower mechanical strength, more expensive than PVC	Lower mechanical strength, higher cost	High-temperature applications, medical equipment	UL 3239, UL 3302
Insulation (Wire/Cable)	PE (Polyethylene)	Lightweight, good dielectric properties, resistant to moisture	Lower temperature range (-65°C to 80°C), less flexible than PVC	Limited temperature range, less flexible than PVC	Telecommunications, low voltage applications	PE-89, PE-39
Insulation (Wire/Cable)	FEP (Fluorinated Ethylene Propylene)	Excellent chemical resistance, wide temperature range (-200°C to 205°C), flame retardant	Higher cost, stiffer than PVC	Higher cost, stiffer than other insulation materials	Harsh environments, aerospace, chemical processing	UL 1330, UL 1659

Material of Housing & Wires when Package

For good checking, please find below table comparing different materials used for wire, housing, and pressure sensor packaging

Component	Material	Pros	Cons	Limitations	Suitable Industries	Examples
Wire	Copper	High electrical conductivity (5.96×10^7 S/m), good flexibility, solderable	Heavier, less resistant to corrosion than aluminum	Susceptible to corrosion in certain environments	Power transmission, data transmission, electronics	AWG, THHN, THWN
Wire	Aluminum	Lightweight, good electrical conductivity (3.77×10^7 S/m), cost-effective	Less flexible, less solderable, prone to oxidation	Oxidation, less flexible, difficult to solder	Power transmission, overhead lines, automotive	AA, AAAC, ACSR
Housing	Stainless Steel	Corrosion-resistant, high strength, durable, good temperature resistance	Heavier, more expensive than plastic	Heavier, more expensive than other materials	Oil and gas, food and beverage, marine, chemical	SS 316, SS 304
Housing	Aluminum	Lightweight, corrosion-resistant, cost-effective	Lower strength than stainless steel, prone to oxidation	Prone to oxidation, lower strength than stainless steel	Automotive, aerospace, electronics, general-purpose	6061, 7075
Housing	Plastic	Lightweight, cost-effective, good chemical resistance	Lower strength and temperature resistance than metals	Lower strength, limited temperature resistance	Consumer electronics, automotive, general-purpose	ABS, Polycarbonate
Pressure Sensor Packaging	Ceramic	Good chemical resistance, stable at high temperatures, electrical insulation	Brittle, more expensive than some metals	Brittle, more expensive than some metals	Oil and gas, automotive, aerospace, chemical	Alumina, Zirconia
Pressure Sensor Packaging	Stainless Steel	Corrosion-resistant, high strength, durable, good temperature resistance	Heavier, more expensive than plastic	Heavier, more expensive than other materials	Oil and gas, food and beverage, marine, chemical	SS 316, SS 304
Pressure Sensor Packaging	Plastic	Lightweight, cost-effective, good chemical resistance	Lower strength and temperature resistance than metals	Lower strength, limited temperature resistance	Consumer electronics, automotive, general-purpose	ABS, Polycarbonate

Material of Wetted Parts

Wetted parts are the components of a pressure sensor that come into direct contact with the process media (liquid, gas, or vapor). Choosing the right material for wetted parts is crucial for ensuring the sensor’s accuracy, reliability, and longevity.

Here are some common materials for wetted parts and factors to consider when selecting them:

Stainless Steel (e.g., SS 316, SS 316L, SS 304)

• Pros: Corrosion-resistant, durable, good strength, good temperature resistance
• Cons: Heavier and more expensive than some other materials
• Suitable for: Oil and gas, food and beverage, marine, chemical industries

Hastelloy (e.g., Hastelloy C276)

• Pros: Excellent corrosion resistance, especially to acidic and chloride environments, good strength, high temperature resistance
• Cons: More expensive than stainless steel
• Suitable for: Chemical, petrochemical, oil and gas, wastewater treatment industries

Monel (e.g., Monel 400)

• Pros: Good corrosion resistance, especially to reducing media, good strength, high temperature resistance
• Cons: More expensive than stainless steel, less resistant to oxidizing environments than Hastelloy
• Suitable for: Marine, chemical, petrochemical, oil and gas industries

Tantalum

• Pros: Outstanding corrosion resistance, high temperature resistance, biocompatible
• Cons: Expensive, limited availability
• Suitable for: Chemical, pharmaceutical, medical industries

Ceramic (e.g., Alumina, Zirconia)

• Pros: Good chemical resistance, stable at high temperatures, electrical insulation
• Cons: Brittle, more expensive than some metals
• Suitable for: Oil and gas, automotive, aerospace, chemical industries

PTFE (Polytetrafluoroethylene)

• Pros: Excellent chemical resistance, non-stick properties, good electrical insulation
• Cons: Limited temperature and pressure range, lower mechanical strength compared to metals
• Suitable for: Food and beverage, chemical, pharmaceutical industries

When choosing a material for wetted parts, consider the following factors:

• Chemical compatibility: Ensure the material is resistant to the process media.
• Temperature range: Choose a material that can withstand the expected temperature range of the application.
• Pressure range: Select a material with adequate strength to withstand the pressure range.
• Cost: Balance the material cost with the desired performance and reliability.
• Regulatory requirements: Comply with industry-specific regulations (e.g., FDA, NSF) if necessary.

Material	Pros	Cons	Suitable Industries	Limitations
Stainless Steel (e.g., SS 316, SS 316L, SS 304)	Corrosion-resistant, durable, good strength, good temperature resistance	Heavier and more expensive than some other materials	Oil and gas, food and beverage, marine, chemical industries	Cost, weight
Hastelloy (e.g., Hastelloy C276)	Excellent corrosion resistance, especially to acidic and chloride environments, good strength, high temperature resistance	More expensive than stainless steel	Chemical, petrochemical, oil and gas, wastewater treatment industries	Cost
Monel (e.g., Monel 400)	Good corrosion resistance, especially to reducing media, good strength, high temperature resistance	More expensive than stainless steel, less resistant to oxidizing environments than Hastelloy	Marine, chemical, petrochemical, oil and gas industries	Cost, oxidation resistance
Tantalum	Outstanding corrosion resistance, high temperature resistance, biocompatible	Expensive, limited availability	Chemical, pharmaceutical, medical industries	Cost, availability
Ceramic (e.g., Alumina, Zirconia)	Good chemical resistance, stable at high temperatures, electrical insulation	Brittle, more expensive than some metals	Oil and gas, automotive, aerospace, chemical industries	Brittleness, cost
PTFE (Polytetrafluoroethylene)	Excellent chemical resistance, non-stick properties, good electrical insulation	Limited temperature and pressure range, lower mechanical strength compared to metals	Food and beverage, chemical, pharmaceutical industries	Temperature and pressure range, mechanical strength

Summary

In conclusion, the selection of materials for pressure sensors is highly dependent on the specific application, industry, and environmental conditions. Understanding each material’s properties, advantages, and limitations is essential to ensure the pressure sensor performs optimally and maintains a long service life.

Different pressure sensor applications require materials with different properties. For instance, sensors used in environments with high humidity, saltwater corrosion, or exposure to harsh chemicals require materials that can withstand chemical attack and resist degradation.

Therefore, material selection for pressure sensor production is vital to ensure that the sensor can meet its intended use for an extended period, offer high measurement accuracy, good repeatability, and reliability. The wrong material selection can lead to sensor failure, lower accuracy, reduced lifespan, and even safety risks due to chemical corrosion, deformation of the measurement component, or even material fatigue.