adccommunitymod (AutomationDirect) asked a question.
dl05 analog input
Created Date: November 07,2000
Created By: schneire
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I am using a dl05 with analog input to read current through a 4-20ma 0-50 amp curren transformer. The problem is when a scale the value at a specific amperage, when I adjust the amperage the read value doesn't coincide any more. The further I move the further it goes away from the real value. I am measuring a split-wave current, and the device is reading in RMS. I am scaling using the formula (v2000 * 500 / 4095)+8(to a line with house standard) Ron
Created Date: November 07,2000
Created by: schneire
I am using a dl05 with analog input to read current through a 4-20ma 0-50 amp curren transformer.
The problem is when a scale the value at a specific amperage, when I adjust the amperage the read value doesn't coincide any more. The further I move the further it goes away from the real value.
I am measuring a split-wave current, and the device is reading in RMS.
I am scaling using the formula
(v2000 * 500 / 4095)+8(to a line with house standard)
Ron
Created Date: November 07,2000
Created by: Tom Jenkins
Skip the +8. V2000 will = 0 at 4 mA and 4095 at 20 mA. Assuming your transmitter and C/T are accurate the formula is:
Amps = V2000 x 500 / 4095 This will give results with an implied one decimal place (amps + tenths). Make sure you do the multiply before the divide to maintain accuracy.
You may have a problem with the C/T. Sometimes on low ratio C/Ts (like a 50:5 C/T) the allowable burden is very low, and even a few dozen feet of #14 AWG wire can be more resistance at high amperge than the C/T can handle. Check the total loop resistance at the C/T, including the transmitter burden. Check your PLC readings against the mA signal and use a clamp on ammeter to check your C/T output.