Common problems encountered when using overpressure transmitters and their solutions

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I. Problem symptoms: No output from the transmitter – Inspection and testing 1. Check whether the power supply to the transmitter is connected reversely； 2. Measure the power supply of the transmitter to check whether there is 24V DC voltage ； 3. If it has a header, check whether the header is damaged (you can first short-circuit the two wires of the header; if it works normally after short-circuiting, then the header is damaged) ； 4. Connect the ammeter in series in the 24V power supply circuit to check whether the current is normal ； 5. Is the power supply connected to the transmitter’s power input terminal? ； Solution 1: Connect the power polarity correctly. 2. It is necessary to ensure that the power supply voltage to the transmitter is ≥12V (i.e., the voltage at the transmitter’s power input terminal is ≥12V). 3. If there is no power supply, check whether the circuit is disconnected and whether the measuring instrument has been selected incorrectly (the input impedance should be ≤250Ω) ； 4. If the header is damaged, it needs to be replaced; if it is normal, this indicates that the transmitter is functioning properly. In such a case, it is necessary to check whether other instruments in the circuit are also working correctly. 5. Connect the power cord to the power terminals. II. Problem symptoms: Transmitter output ≥ 20mA – Inspection and testing: 1. Check whether the transmitter’s power supply is functioning properly. 2. Determine whether the actual pressure exceeds the range selected for the pressure transmitter ； 3. Check whether the pressure sensor is damaged; severe overloading can sometimes damage the diaphragm. 4. Are the connections loose? ； 5. Is the wiring of the power cable correct? Solutions: 1. If the transmitter’s power supply voltage is less than 12VDC, check whether there are any heavy loads in the circuit; the input impedance of the transmitter’s load should satisfy RL ≤ (Transmitter supply voltage – 12V) / (0.02A) Ω. 2. Select a pressure transmitter with an appropriate range. 3. If the pressure sensor is damaged, it must be sent back to the manufacturer for repair. 4. Connect the wires and tighten them. 5. The power cord should be connected to the corresponding terminal. III. Problem symptoms: Transmitter output ≤ 4 mA – Inspection and testing: 1. Check whether the transmitter’s power supply is functioning properly. 2. Determine whether the actual pressure exceeds the range selected for the pressure transmitter ； 3. Check whether the pressure sensor is damaged; severe overloading can sometimes damage the diaphragm. Solution 1: If the power supply to the transmitter is less than 12VDC, it is necessary to check whether there are any heavy loads in the circuit. The input impedance of the transmitter’s load should satisfy the condition RL ≤ (Transmitter supply voltage – 12V) / (0.02A) Ω. 2. Select a pressure transmitter with an appropriate range again. 3. If the pressure sensor is damaged, it must be sent back to the manufacturer for repair. IV. Problem phenomena: Incorrect pressure indication – Inspection and testing 1. Is the power supply to the transmitter functioning properly? 2. Is the reference pressure value accurate? 3. Is the range of the pressure indicating instrument consistent with that of the pressure transmitter? 4. Are the inputs of the pressure indicating instrument connected correctly? 5. The input impedance of the transmitter’s load should satisfy RL ≤ (Transmitter supply voltage – 12V) / (0.02A) Ω. 6. Is the input terminal open circuit when the multi-point paper recorder is not recording? ； 7. Is the corresponding equipment enclosure grounded? 8. Are the wiring paths separated from those of the AC power supply and other power sources? 9. Is the pressure sensor damaged? Severe overloading can sometimes damage the diaphragm. 10. Are there any sands, impurities, etc. inside the pipeline that could block it? The presence of such impurities can affect the accuracy of measurements ； 11. Is the temperature of the pipeline too high? The operating temperature range for the pressure sensor is -25~85°C, but in practice it should be within the range of -20~70°C. Solution 1: If the transmitter’s power supply voltage is less than 12VDC, it is necessary to check whether there are any heavy loads in the circuit. The input impedance of the transmitter’s load should satisfy the condition RL ≤ (Transmitter supply voltage – 12V) / (0.02A) Ω. 2. If the accuracy of the pressure gauge being used is low, a pressure gauge with higher accuracy should be used instead. 3. The range of the pressure indicating instrument must be consistent with that of the pressure transmitter. 4. If the input for the pressure indicating instrument is 4~20mA, the transmitter’s output signal can be connected directly ； If the input to the pressure indicating instrument is 1–5V, a resistor with a precision of at least one thousandth and a resistance value of 250Ω must be connected in parallel at the input of the pressure indicating instrument, before connecting it to the transmitter’s input. 5. The input impedance of the transmitter load should meet the condition RL≤; if not, appropriate measures can be taken depending on the specific situation: for example, increasing the supply voltage (but it must remain below 36 VDC) or reducing the load. 6. If the input terminal of a multi-point paper recorder is open when no recording is taking place, then: 1. It cannot drive any other loads ； 2. Switch to another recorder that has no recorded input impedance of ≤250Ω. 7. The corresponding equipment enclosure shall be grounded. 8. Run the wires separately from AC power and other power sources. 9. If the pressure sensor is damaged, it must be sent back to the manufacturer for repair. 10. When sand, impurities, etc. inside the pipeline cause blockages, these impurities must be removed, and a filter screen should be installed in front of the pressure connection. 11. If the temperature of the pipeline is too high, use a buffer tube to dissipate heat. Fill the buffer tube with cold water before use to prevent overheated steam from directly hitting the sensor, which could damage it or reduce its service life