Knowledge about Flush Diaphragm Pressure Transmitter

Knowledge about Flush Diaphragm Pressure Transmitter

by | Jul 28, 2017

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The Flush Diaphragm Pressure Transmitter or transducer can do the same job which other conventional thread connection product can do,  such as convert the applied pressure into an output signal of 4~20mA @ F.S pressure.

However, Flush Diaphragm Pressure Transmitter is also designed to be installed in a series of hazardous situation and is ideal for use in food, beverage sanitary, medical process and industrial applications where the media is either viscous, contains particulates or solids, which may probably cause the clog or foul.

What is Flush Diaphragm Pressure Transmitter?

The definition can come to many ways but the commonsense recognize that a Flush Diaphragm Pressure Transmitter is the one with flat surface at the end of the sensor, beyond the process threads and can be deployed in conjunction with viscous fluid or media that may clog a standard process connection or may be otherwise liable to block a standard inlet port as the diaphragm of flush type is open/flush mounted with no cavity.

A Simple Experiment

Let’s grab an egg and place it the palm of your hand, with the pointed end of the egg directed toward your fingers. Close your hand around the egg and squeeze. If you’re doing it properly, your fingers will be pressing down on the pointed end of the egg, and the rounded end will be settled in your palm.

You can squeeze as hard as you can and the egg won’t break. That’s because you’re applying even pressure where the egg is strongest. The eggshell is designed to withstand that kind of abuse. However, if you hit any part of the egg on any surface, it will crack.

A pressure sensor diaphragm is like an eggshell. It can withstand incredible pressure when it is applied evenly across the entire surface. However, putting pressure on a single area or point of the diaphragm will cause problems.

That’s because the diaphragm is very thin – a few thousandths of an inch. It’s actually quite impressive that such a thin sheet of metal can withstand high pressure – tens of thousands of pounds per square inch.

But when an object focuses pressure on a small area or point, the thin diaphragm will be damaged and the sensor may need to be recalibrated or replaced.

The Diaphragm

With most process connections, we can recess the thin diaphragm to protect it from contact with anything other than the process media. However, flush mount diaphragms remove that protection. Instead, the diaphragm is the flat surface at the end of the sensor, beyond the process threads.

The flush mount exists primarily for two major benefits:

  1. There is no recess that can become fouled or clogged.
  2. The sensor can measure flush to the pipe or vessel wall, reducing resistance and maintaining flow.

For the right application, these pros outweigh the cons of having an exposed diaphragm that must be handled carefully. You must keep anything from touching the sensor’s diaphragm except for the process media.

How Torque Affects Flush Mount Diaphragm?

It’s admitted that the torque applied during the installation or mounting process can significantly affect the performance and accuracy of flush mount diaphragm pressure sensors. Here’s how torque affects flush mount diaphragm sensors:

Diaphragm Deformation

The diaphragm is the sensing element in a flush mount pressure sensor, and it is designed to deflect or deform in response to applied pressure. When excessive torque is applied during the mounting process, it can cause mechanical stress and deformation of the diaphragm, even before any pressure is applied. This pre-stressed condition can lead to inaccurate pressure readings and potentially shift the sensor’s zero point.

Stress Concentration

Flush mount diaphragm sensors are typically designed with a thin, flexible diaphragm that is flush with the sensor body. When torque is applied unevenly or excessively during installation, it can create localized stress concentrations on the diaphragm, leading to non-uniform deformation and potential diaphragm failure or fatigue over time.

Hysteresis and Non-linearity

Excessive torque can introduce hysteresis and non-linearity in the sensor’s response. Hysteresis refers to the phenomenon where the sensor output differs depending on whether the pressure is increasing or decreasing, while non-linearity means that the sensor’s output is not proportional to the applied pressure across the entire measurement range. These effects can compromise the sensor’s accuracy and repeatability.

Hysteresis Pressure Sensor-eastsensor

Sensitivity Shift

The sensitivity of a flush mount diaphragm sensor, which is the ratio of the output signal to the applied pressure, can be affected by excessive torque. The mechanical stress induced by torque can alter the diaphragm’s deflection characteristics, leading to a shift in the sensor’s sensitivity, which can cause measurement errors.

To mitigate the effects of torque on flush mount diaphragm pressure sensors, manufacturers typically provide installation guidelines and recommended torque values. These guidelines are based on the specific sensor design, materials, and intended application. Following these recommendations is crucial to ensure accurate and reliable pressure measurements.

Additionally, some flush mount diaphragm sensors are designed with torque-insensitive features, such as isolation rings or reinforced diaphragm structures, to minimize the impact of torque during installation. These design features help to decouple the diaphragm from the mounting stresses, enhancing the sensor’s performance and accuracy.

You might be thinking that these sensors sound like they can’t hack it in the real world. They certainly can and do with regularity. They simply require careful handling and installation.

Again, the pros outweigh the cons in the right applications. It’s simply the nature of exposing the sensing elements of a transducer designed to be responsive to small changes in pressure.

Highlight Features of EST330F

In terms of different situation, Eastsensor produce two kinds of Flush Diaphragm Pressure Transmitter,

  1. The normal type flush diaphragm
  2. The Tri-clamp mounting open face flush diaphragm

Both of them are made ruggedly by SS316L and can be deployed in critical process filed to eliminate any cavity that could form a clog.

 

EST330F Features goes below

  • Unique flush stainless steel diaphragm eliminates any cavity that could form a clog
  • SS316-gthick diaphragm provides higher overpressure and spike protection
  • Available ranges up to 500 psi
  • Wide range of mechanical and electrical connections
  • ±0.50% accuracy
  • Working temperature up to 150 ℃ (customized)
  • IP65 with HSM/DIN43650 and IP68 with cable connection
  • 1 year Warranty
  • OEM available

 

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What is The Difference between Pressure Transducer and Pressure Transmitter?

What is The Difference between Pressure Transducer and Pressure Transmitter?

by | Nov 29, 2016

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More and more people tend to ask what the difference between pressure transducer and pressure transmitter is and what the difference between pressure sensor and pressure transducer is as well. Actually, in EastSensor, our engineers make comprehensive sturdy and consultant then come up with below points to help customers, no matter within or not the measurement instrument filed to have a better understanding among their meaning.

As a matter of fact, the exact definition of these terms are usually interchanged from case to case, but we’d admit that they have general definition as below

Pressure Sensor

A millivolt output signal generally. Millivolt (mV) output signal (also a general term for all pressure types); a device that measures pressure. The millivolt output signal can typically be used ten (10) to (20) feet away from the electronics without significant signal loss.

The signal is proportional to the supply. A 5VDC supply with a 10mV/V output signal produces a 0-50mV output signal. Older technologies such as bonded foil strain gage or thin film technology produce 2-3mV/V (millivolts per volt), whereas MEMS technology can produce 20mV/V reliably.

Millivolt output signals give the design engineer the flexibility to condition the output signal as their system needs it and can reduce package size and cost.

Millivolt Output Pressure Sensor 0-100

Pressure Transducer

An amplified voltage output typically. Transducers are voltage-output devices that can be used with simple signal conditioning but are more sensitive to electromagnetic interference.

The electrical resistance of the connecting cable can cause significant errors if the cable is long. They require three or four connecting wires to supply power and deliver the output signal.

Click to find more details about Why you need Millivolt Output Pressure Transducer?

Pressure Sensor Output signal-2

Pressure Transmitter

Always output 4~20mA signal. Transmitters are current-output devices and may have two or three wires. Where two wires are used to both receive power and transmit an output signal, significant cost savings can be made where long cables are needed.

They are frequently scaled to vary from 4 mA to 20 mA as the pressure varies from minimum to maximum. Thus the on-board electronics has to be capable of operating with a maximum current drain of less than 4 mA.

Being ‘current driven’, the in-built circuitry controls the voltage across the transmitters’ two terminals to ensure that the appropriate pressure-proportional current is maintained irrespective of line resistance up to a specified limit.

Thus these devices are very suitable for use with long cables and are much less susceptible to electromagnetic interference than voltage-output transducers. Sometimes called current loop or serial devices, additional displays at different locations can easily be included in the loop without degrading the output signal. Such devices normally suffer no significant degradation of signal output with distance.

4-20mA Pressure Sensor-proportion

Digital output transmitters normally contain a microprocessor which converts measured pressure values into digital codes which are transmitted to a remote receiver, or ‘host’, via wires, optical fibres or radio. There are a number of standard systems available, such as Fieldbus (IEC 1158) and HART, the latter having the facility to operate in combination with the more traditional 4 mA to 20 mA current-output systems.

Beyond supplying pressure values, digital transmission can include diagnostic information, status and alarms and can also facilitate remote reconfiguration of transmitters.

Once the difference can be described to the definition of signal output, the question can be set. Below is a general guideline on such terms and some advantage and disadvantage.

The Difference Between Pressure Transducer and Pressure Transmitter

Pressure Transducer: 

High level voltage or frequency output signal including 0.5 to 4.5V ratiometric (output signal is proportional to the supply), 1-5V and 1-6kHz.

These output signals should be used within twenty (20) feet of the electronics. Voltage output signals can offer low current consumption for remote battery operated equipment. Supply voltages are typically from 8-28VDC, except for the 0.5-4.5V output, which requires a 5VDC regulated supply.

Older voltage output signals, such as 0-5V, do not have a “live zero” where there is signal when the sensor is at zero pressure. The risk is that the system does not know the difference between a failed sensor with no output and zero pressure.

0.5-4.5V Pressure Sensor regulated 5v supply

Pressure Transmitter: 

Current output signal, i.e. 4-20mA (4 to 20mA), the current, rather than the voltage, is measured on the device, rather than the voltage; EastSensor pressure transmitters also have many types of two wire devices (red for supply, black for the ground). 4-20mA pressure transmitters offer good electrical noise immunity (EMI/RFI), and will need a power supply of 8-28VDC.

Because the signal is producing current, it can consume more battery life if operating at full pressure.

Pressure Transducers are available with a variety of voltage output options.

With advances in controllers that receive the transducer signal, there is more flexibility in the marketplace. There are minor differences between many of the output options on the market place. While some developed to maintain competitive advantages via customized products, others have solid reasoning.

The outputs reviewed here are all powered by a minimum of 10VDC (0-10V and 1-10V outputs need 12VDC). A 0.5-4.5V ratiometric output signal is traditionally powered by a 5VDC regulated supply, yet other variations are possible. In a similar way, millivolt output signals have their own unique features and benefits. The following is a brief introduction to amplified voltage pressure transducers.

The Difference Between Pressure Transducer and Pressure Transmitter 3 wire and 4 wire

Zero based output

Traditional pressure transducer outputs include 0-5V and 0-10V signals. Popularized in Europe, zero based output signal produce no output signal at zero pressure in a standard gauge pressure transducer.

Transducers are offered in three wire and four wire configurations with zero based output signals. The advantage of the 0-10V signal is that it has twice the span as the 0-5V. The main disadvantage to any zero-based output signal is that there is no signal with zero pressure.

If the transducer has a cut wire, broken sensing element, or electronics that received an over-voltage, the sensor will produce no signal, thus no way to know of a problem. If we assume that the pressure transducer is measuring water pressure, it will produce a 0V signal when there is no pressure in the line.

Voltage Output Pressure Sensor

When pressure is sensed, it will signal the pump to act. Since the sensor at 0V is the same in fault conditions and at no pressure, there is no way to distinguish between the two. The pump would not know to run, and could cause a flooding condition.

Voltage at zero pressure

There are many variations and custom options for pressure transducers with an output signal at 0 PSI. For example, EastSensor offers 1-3V, 1-5V (for Automotive Industry), and 0.5-4.5V. The 1-5V output signal is most popular in the industry. There is the safety feature of having a 1 volt output signal at zero pressure and a 4 volt span for pressure measurement. 1-3V and 1-5V output signals are popular among engineers who prefer a voltage span similar to the zero based outputs above, but with the signal at zero pressure. The 0.5-4.5V output signal is somewhat unique.

For remote telemetry applications, current consumption is a common factor. Because lithium-ion batteries or solar panels create power in remote oil fields and on construction site equipment, having a low power supply voltage and low current consumption extend the service life of the pressure transducer.

The 0.5V 0PSI signal gives enough indication that the transducer is working. The span to 4.5V gives enough resolution to accurately measure the pressure or level

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