Who has experience dealing with interference?
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Who has experience dealing with interference? It’s like this: there’s a pressure gauge installed on the extruder, and it keeps showing high readings. Sometimes it gives high readings even when the machine is shut down. We’ve tried replacing the sensor, transmitter, and the on-site display instrument, but the problem persists. It happened twice today. We checked and tested the connection wires, and no issues were found. It’s strange – when the door of the instrument cabinet is opened, the alarm goes away automatically. You might think it’s a problem with the wiring terminals (in practice, the sensor signals are sent to the transmitter, which then sends the signals to the on-site display instrument installed on the cabinet panel; another set of signals is sent to the DCS. When an alarm occurs, both the on-site display instrument and the DCS show it). We’ve checked the wiring terminals several times, and no problems were found. The quality can’t be that poor, right? The terminal is loose; it can’t be detected in 2/3 of the cases. So interference is suspected, but it’s not clear where the interference is coming from
If possible, try a transmitter from another brand. Generally speaking, interference should be present continuously. Check the real-time trend of the measurement values; if there is interference, spikes, that is, sudden changes, will appear. Check whether the grounding of the shield wire is proper; try both single-point grounding and double-point grounding – sometimes that will solve the problem ； Measure whether there is voltage between the shield wire and ground. Try running another cable. Check whether the cabinet’s grounding wire is in good condition. Ensure insulation between the cabinet and the bracket, then connect it to the ground wire via a grounding cable. I can only give it a try.
The question you mentioned is indeed very strange; it’s hard to believe such a phenomenon could occur when one isn’t at the scene. I think the problem lies with the two cables that have overreported readings; short circuits can occur temporarily, and it’s difficult to identify them.
The secondary meter should be checked first; there might be electromagnetic interference, so improve the grounding and see what happens, especially in that pressure detection circuit； If nothing else works, check the circuit connection wires
1. First, check whether the signal cable is in the same trunking as the 220VAC and 380VAC cables, and measure the induced voltage； 2. Inspection of other sources of electrostatic interference, such as capacitive coupling sources, inductive coupling sources, and electromagnetic field coupling sources ； 3. Grounding test: whether it meets the design requirements ； 4. Eliminate external strong magnetic interference sources, such as disabling walkie-talkies, mobile phones, etc.
The interference from the extruder is quite strong; it is recommended to add a signal processor module with safety isolation, which should help improve the situation. Last edited by Shaboluang on 2009-3-17 at 18:25.]