Pressure sensors are rugged and durable devices built to withstand the rigors of industrial use. Many pressure transducer problems are caused by improper installation or by using a pressure sensor that is in appropriate for the application. When you’re troubleshooting pressure sensor problems, the first step is to ascertain that the device in place is the right one for its environment.
Unfortunately, pressure transducer installation sometimes fails. Common issues include:
- Improper wiring
- Incorrect polarity
- Short circuits
- Inadequate power supply
- Multiple grounds
- System operations issues
With these issues, there are simple troubleshooting techniques to determine if the transducer is operational.
- Troubleshooting a 3-Wire Transducer Removed from a Pipeline
The 3-wire voltage output sensor is the most commonly used voltage transducer and it is the easiest to troubleshoot. Most likely, the problem with this type of unit is either no signal or the signal is different from what was expected. After the pressure sensor has been removed from the pipeline and control circuit, you must identify all terminals for the unit being examined. Once terminal configuration has been determined, you can power the unit and check if the transmitter is operating properly through placing the voltmeter + lead onto the + signal and vice versa. If the reading is what was expected, then the sensor is operational.
- Troubleshooting a 3-Wire Transducer Connected to a Pipeline
First make sure that the +24 VDC is connected to the pressure sensor’s + excitation and -24 VDC to common.
- Troubleshooting a 4-Wire Transducer Removed from a Pipeline
Once the unit has been removed form the pipeline and control circuit and terminal configuration has been determined, you can power the unit by connecting the +24 VDC power supply to the transducer’s + excitation and – 24 VDC to the – excitation. Once the voltmeter is connected to the correct signal, when no pressure is applied, the voltmeter reading should equal the analog signal for zero applied pressure.
- Troubleshooting a 4-Wire Transducer Connected to a Pipeline
Once the pressure sensor is connected to the pipeline and control circuit, disconnect the wire that runs from the transmitter’s + signal to the control circuit. Next place the digital voltmeter leads onto the matching transducer signal. If the transmitter provides a voltage output as specified on the unit’s data sheet then the transmitter is operational with one caveat. If it’s reading 0.0 VDC, it has yet to be determined if the transducer is truly functioning.
- Troubleshooting a 4-20mA Transducer Removed from a Pipeline
Once the pressure transducer is powered, the 4-20 mA flows from the transducer’s – terminal that that is then connected to the + lead of a digital milliamp meter. The meter’s – lead is then connected to the – terminal of the 24 VDC power supply. The voltage that is developed in the internal dropping resistor is converted to a milliamp value displayed on the meter’s screen. If the milliamp readout is 4 mA with no pressure applied, it’s operational.
- Troubleshooting a 4-20mA Pressure Sensor
When the transducer is still connected to the pipeline and control circuit, connect the 24 VDC to the red wire of the pressure sensor. Next, disconnect the wire form the transducer that is connected to the control circuit and place the + lead form the digital milliamp meter to the black wire. Now connect the – lead from the digital milliamp meter to the lead going to the control circuit. If the transducer provides 4 mA output signal with no pressure applied, then the sensor is operational.