Close enough?

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NE (9.06 miles @5.9 Degrees from Winged Horses)
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EC - retired
We used some 4-20ma current transducers to monitor the current on 4 motors. To make it short the displayed current, via PLC and HMI, is a bit low, 1- 2 amps, when we compare it to our amp clamps. Using the same setup with a different PLC on other jobs with comparable ranges delivers a closer tolerance.

For my purposes I can scale the results to whatever I want but how close are the adjustable overload settings of the starters we use? My FLA may be 24.6 amps but there is no way my glasses focus well enough to dial that in on most of the ones we see.
 

Smart $

Esteemed Member
Location
Ohio
We used some 4-20ma current transducers to monitor the current on 4 motors. To make it short the displayed current, via PLC and HMI, is a bit low, 1- 2 amps, when we compare it to our amp clamps. Using the same setup with a different PLC on other jobs with comparable ranges delivers a closer tolerance.

For my purposes I can scale the results to whatever I want but how close are the adjustable overload settings of the starters we use? My FLA may be 24.6 amps but there is no way my glasses focus well enough to dial that in on most of the ones we see.
You didn't say which ones you use... but if they are the typical adjustable overloads probably +/- 10%. I'd just scale the results.
 

Crohnos01

Member
Location
BG, Washington
In my experience, low amperage readings with CT's can be a bit iffy on accuracy depending on the manufacturer. On low amperage applications like 1 or 2 amps as you describe, I have found it helpful to loop the conductor through the CT two or more times to increase the accuracy.... might help, can't hurt.
 
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