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Common Malfunction and Solutions of 4~20mA Pressure Transmitter
2018-10-15



Pressure transmitter is widely used in industrial process control applications and 4~20mADC is the most adopted output signal. Here are 4 typical common malfunctions and solutions about 4~20mADC pressure transmitter, helping customers solve the problems quickly on site.


Typical Malfunctions and Solutions


No Display, No Output


Check and Test

Solutions

Check if the power supply is reversed

 

Put it in the correct way.

Check the power supply of pressure sensor if it is 24VDC.

Make sure the pressure transmitter is power supplied ≥12V(intelligent type)≥15V(general type)

If there is no power supply, Check if the circuit is open and detect the secondary instrument/PLC sampling resistance (input impedance should be ≤250Ω)

If it is a displayable pressure transmitter, check if the indicator is damaged (you can short the two wires of the indicator first. If it is normal after short circuit, it means the indicator is damaged)

 

Replace the indicator.

Connect the ammeter to the 24V power circuit and check if the current is normal.

 

If it is normal, the pressure transmitter is normal. In this case, check if other instruments in the circuit are normal.

Check if the wiring is loose or not.

Make it tightened and well connected.

Check if the power supply is correctly connected to power input terminal.

Connect to the power supply terminal correctly according to the power supply requirements


Pressure transmitter output is ≥20mA.


Check and Test

Solutions

Check if the pressure transmitter power supply is normal

If it is less than 12VDC, check whether there is a large load in the circuit. The load capacity of the pressure transmitter should be in accordance with RL ≤ (transmitter supply voltage -12V) / ( 0.02A) Ω

Check whether the actual pressure exceed full range limits

Change a pressure transmitter with appropriate range.

 

Check whether the pressure sensor is damaged. Severe overload sometimes damages the isolated diaphragm

Return the pressure transmitter to the factory for maintenance

Check whether the power supply wiring is correct

Put it in correct way.


Pressure transmitter output is ≤4mA


Check and Test

Solutions

Check if the pressure transmitter power supply is normal

If it is less than 12VDC, check whether there is a large load in the circuit. The load capacity of the pressure transmitter should be in accordance with RL ≤ (transmitter supply voltage -12V) / ( 0.02A) Ω

Check whether the wiring is loose or not which causes the contact resistance to increase. It is equivalent to the load increase.

 

Connect the wire and tighten it, the load is in accordance with RL ≤ (transmitter supply voltage -12V) /

( 0.02A) Ω

Check whether the actual pressure exceeds the selected range of the pressure transmitter

Change a pressure transmitter with appropriate range.

Check whether the pressure sensor is damaged. Severe overload sometimes damages the isolated diaphragm

Return the pressure transmitter to the factory for maintenance


Wrong display/output signal with error


Check and Test

Solutions

Check if the pressure transmitter power supply is normal

If it is less than 12VDC, check whether there is a large load in the circuit. The load capacity of the pressure transmitter should be in accordance with RL ≤ (transmitter supply voltage -12V) / ( 0.02A) Ω

Check if the reference pressure value is correct.

Replace the same type pressure transmitter, if the error is consistent, check the reference pressure meter. If the meter accuracy is low, you need to change the instrument with higher precision.

Check if the range of the secondary meter consistent with the range of the pressure transmitter

 

Adjust the range of the secondary instrument to make sure it is consistent with the range of the pressure transmitter

The capacity of the pressure transmitter load should be in accordance with RL ≤ (transmitter supply voltage -12V) /

( 0.02A) Ω

If it is not, take measures according to its different conditions: such as raising the power supply voltage (but must be lower than 36VDC), reducing the load, etc.

Check if the corresponding device housing is reliably grounded

If not, make it reliably grounded.

Check whether the strong and weak electricity are separately arranged onsite.

 

Make sure the wiring is scientific and reasonable, avoiding interference for pressure transmitter signal instability / error

The pressure sensor diaphragm is easily deformed. Overload and hard objects may damage the isolated diaphragm.

Return the pressure transmitter to the factory for maintenance

Check the pipeline When the pipeline has impurities, the measurement accuracy will be affected.

Clean the impurities and add filter screen before the pressure port.


Contact Us

Above are common malfunctions and solutions for 4~20mADC pressure transmitters, while there are other analog and digital pressure transmitters and common malfunctions also. We cannot list them all. If you have problems for pressure measuring and sensing, feel free to contact us via sales@microsensor.cn. Our professional sales will reply you within 24 hours.