Can inverters interfere with the signal of electromagnetic flowmeters?
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The electromagnetic flowmeter outputs a 4–20mA signal. The frequency converter is located very close to the flowmeter; could the frequency converter interfere with its signal? Are there any solutions for this?
This post was last edited by zhaohh3211 on 2010-6-3 at 15:23. Interference is inevitable; it can be reduced by using shielded cables for grounding. The interference caused by current signals is much less than that caused by voltage signals. In Siemens frequency converters, interference at 0-10V levels is more severe, but it generally does not affect normal operation.
Additional note: The cable from the inverter to the motor is also a shielded cable, an output reactor is used, and the inverter enclosure is properly grounded.
Try to use two power supplies for the frequency converter and flow meter
If the inverter has a high power rating, in addition to what has been mentioned above, an input reactor should be installed as much as possible. Moreover, there are also specific requirements regarding the point at which the signal cables connecting the inverter to the DCS system are grounded for shielding purposes; it is best to ground them at the inverter side rather than at the DCS cabinet
Interference will exist to some extent; as the power of the inverter increases, the interference also intensifies, but it should not affect normal use. If you are concerned, you can take some measures to reduce interference: 1. Use shielded cables as much as possible, and ground the shielding layer in accordance with the specifications. 2. The 4-20mA model circuits use active signal isolators. 3. The inverter enclosure is properly grounded.
If there is interference, add an isolator to the signal line of the electromagnetic flowmeter. Then there definitely won’t be any impact. We have encountered it too. With it added, there is no interference.
Signal isolators are divided into two types: active and passive. Active signal isolators perform very well, but they are expensive. Passive signal isolators have relatively poor performance, but they are very cheap. Which one to use depends mainly on the importance of the location of use.