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How can you tell what the problem is when the pressure transmitter has no output?

Dec 12, 2018

How can you tell what the problem is when the pressure transmitter has no output?

Pressure transmitter is a kind of common pressure instrument, which is often used to measure pressure, liquid level and so on.The function of pressure transmitter is to measure the liquid level, density and pressure of liquid, gas or steam, and then convert the pressure signal into 4-20madc signal output to supply secondary instruments such as indicator alarm, recorder and regulator for measurement, indication and process adjustment.Pressure transmitter is a field instrument in direct contact with the medium under test. It often works in high temperature, low temperature, corrosion, vibration, impact and other environments.Pressure (differential pressure) transmitter main measurement parameters are pressure or differential pressure, but they can indirectly measure a lot of parameters.


How can you tell what the problem is when the pressure transmitter has no output?

Pressure transmitter pressure sensitive core USES high-performance silicon piezoresistive pressure oil core body, the internal dedicated integrated circuit will sensor millivolt signal into 4-20 milliampere standard voltage, current or frequency signal, can be directly connected to the control instrument, intelligent instrument or PLC and other convenient.Realize operation distance observation and control reading.With small volume, light weight, all stainless steel sealing structure, can work in bad environment.This series of pressure transmitter is easy to install and simple, with high anti - vibration and anti - impact performance.Widely used in production process control, aerospace, automotive, medical equipment, tap water, chemical, petroleum and other fields.


2 main faults of pressure transmitter and their treatment methods:


1. Pressure transmitter has no display and no output.Want to check wiring mode above all whether connect an opposite, or wiring place appears loose again.If there is no above reasons to check whether the power supply is normal, usually the power supply of the transmitter is 24V, the current is too small to drive the transmitter, the current is too high will easily lead to the transmitter circuit board burnt out so that no output no display.If the place of use is outdoors, waterproof measures should be taken, the cover of the transmitter should be tightened, and waterproof measures should be taken when wiring out. If rainwater infiltrates into the transmitter, the circuit board of the transmitter will be burnt out, thus no output will be displayed.


2. Pressure transmitter indication is not correct, the first thing to determine whether the reference pressure value must be correct, small make up also encountered the scene with 1.5% accuracy of the pressure gauge to determine the accuracy of 0.25% pressure transmitter.First of all, it is necessary to determine whether the indicator is abnormal or abnormal transmitter indicator.In addition, check whether the corresponding wiring is normal, whether the equipment shell is grounded, whether the pressure sensor is damaged, serious pressure overload will damage the sensor, so that the pressure indicator is not normal.


How can you tell what the problem is when the pressure transmitter has no output?

When the scene without output pressure transmitter, we first need to decide what is the problem, rather than simply think there is something wrong with the pressure transmitter, because in many applications, in addition to the used alone, and may be combined with other equipment or systems, such as orifice plate, such as digital display table, such as flow meter.

Let's talk about it in a few different ways:


1, If the pressure transmitter and digital display table with the use of this time, if the digital display table does not show, then the user may say that the pressure transmitter has no output (often encounter a call user said so), in fact, this problem is very obvious, hastily determined that the pressure transmitter has no output is unreasonable.If pressure transmitter normal output, digital display table appeared fault, is also possible.This is the user's understanding of the site fault judgment error.So how to determine whether the pressure transmitter is normal output?Very simple, use a multimeter to directly measure the output end of the pressure transmitter, whether to use 4-20ma current value can be measured.Of course, when used in conjunction with other instruments this situation occurs, as the first multimeter to determine the current measurement.


How can you tell what the problem is when the pressure transmitter has no output?4

2. We know that the transmitter needs 24V power supply. If the pressure transmitter has no output, we should first consider whether there is 24V power supply or whether the 24V power supply is normal.However, if the scene as described in the first point, and the digital display meter or other built-in 24V power supply table in series, then the pressure transmitter does not need to provide 24V power again.This second aspect is for the use of pressure transmitter alone when.


3. If the 24V power supply is available and the power supply is normal, and the pressure transmitter has no output at this time, it is necessary to check whether the power line is connected to the wrong side, and whether the positive and negative poles are connected to the wrong side.


4. If the wiring is correct, it is necessary to check whether there is line break in the whole circuit;Or check to see if the instrument selection error (such as input impedance should be 250 Ω) or less.


5. If all the above inspections are normal, it may be that the hardware of the pressure transmitter fails.For example, at the beginning of the field pressure transmitter, there was a problem with the 24V power supply, which caused the circuit board of the pressure transmitter to burn out. Of course, there was no direct display and no output.For example, the selected pressure transmitter's overload and pressure tolerance are not in line with the conditions on the site, and excessive pressure may lead to the damage of pressure transmitter components, and no output of pressure transmitter.For example, the pressure transmitter is with field display, that is, with the head, if the head is damaged at this time, then there will be no output pressure transmitter.If you judge whether the head is damaged, the two lines of the head of the direct short circuit, if the short circuit is normal, it is damaged.