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Power meter kW over Modbus is ten times the clamp meter reading

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 edj
(@edj)
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Joined: 2 years ago
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Topic starter   [#203]

Put a panel power meter on the compressor MCC feed, Modbus RTU, 600:5 CTs, reading it into a CompactLogix through a Modbus gateway. The meter's own display says 187 kW and 231 A, which is what the clamp on the feed says as well.

The register in the PLC comes in at 1874 for kW and the amps register at 2310. kVA, kVAR, every one of them ten times what the display shows. I swapped the word order in the gateway and got garbage in the millions, so I put it back, and the CT ratio in the meter checks out, 600 primary and 5 secondary. Bit stuck now.

Meter and clamp agree with each other and the PLC is the odd one out. is there a decimal setting in the meter that the display honours and the register doesn't?


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(@scott_m)
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Joined: 1 year ago
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Every register out by exactly ten is scaling, not word order. Word order gives you the garbage you already saw. Which meter is it, and does the register map have a scale or multiplier column next to the kW register?



   
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