Troubleshooting for Pressure Transducers
Pressure transducers have never been more prevalent, or more reliable. With stainless steel construction and modern engineering, pressure transducers can provide overpressure protection, improved total error band, and negligible orientation and vibration effects. They are ideal for long-term use in harsh environments of extreme temperature, humidity, and vibration. However, pressure transducers can fail like any other piece of equipment. Common causes include improper wiring, incorrect polarity, inadequate power supply, multiple grounds, short circuits, operations issues, and problems with the transducer itself. In this blog, we’ll explore some trouble-shooting techniques that can help you determine just what went wrong with your transducer.
Before we begin, however, these troubleshooting guidelines assume that the person following them is a trained technician, has access to a 24 VDC power source, and knows how to properly use a digital multimeter to measure resistance, current, and voltage.
When trouble-shooting a 3-wire transducer, the most commonly used voltage transducer, the problem is most likely that there is no signal or that the signal is different from what is expected. After removing the transducer from the pipeline and control circuit, the technician needs to identify all terminals for the unit being examined. Once terminal configuration is confirmed, the technician can power the unit and check if the transmitter is operating properly through placing the voltmeter + onto the +_ signal and vice versa for the - components. If the readings are what the technician expected, then the transducer is operational.
When the 3-wire transducer is still attached to a pipeline, make sure that the +24 VDC is connected to the transducer’s + excitation, and the -24 VDC to the common. Then, disconnect the wire that runs from the transducer’s + signal to the control circuit. Place to voltmeter’s + lead onto the transducer’s + signal, and the voltmeter’s - onto common. With no pressure applied, the transmitter should provide a voltage output that is specified on the unit’s data sheet. If it does, then the transducer is functioning properly.
When troubleshooting a 4-wire transducer that has been removed from the pipeline, as well as its control circuit and terminal configuration, the technician 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 and no pressure is applied, the voltemeter should provide a reading that is equal to the analog signal for zero applied pressure.
When troubleshooting a 4-wire transducer that is still connected to a pipeline, 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 by the unit’s data sheet, then the transmitter is operational. However, if the transmitter reads 0.0 VDC, it may not be functioning, and further troubleshooting will need to be conducted.
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