Reading analog inputs

[chand345]

Hey,

For some reason my UIA-0800N is getting readings without my CT being plugged in its a fluctuating number and its happening with all inputs. Also does anyone know how to scale a CT(current transducer) and why when i put a constant voltage source in as an input it still fluctuates?

 

Thanks

[AlexUT]

Please check if your CT device is compatible with UIA-0800N  module.

And if you configured right UIA-0800N  current loop channel.

You have to use linearization to convert current loop input to engineering value.

B.R.

 

[chand345]

Thanks for the response,

What determines whether or not your CT is compatible? I put 0-10V as the electricity type because the CT returns voltage which the black wire was in CM0 port and the white wire was in the I0V port and I tried smoothing and  noise rejection but it still returns a fluctuating number. What could I be doing wrong. Also, the ct's we are using are for  test we are using different CT's for the final product of the system just an FYI.

Any suggestions?

[AlexUT]

If you mean CT is a Current Transformer, then output is current, not voltage.

For current input you have to configure analog input in hardware configuration as current, and use I input.

For voltage input you have to configure analog input in hardware configuration as voltage, and use V input.

B.R.

 

[chand345]

The CT takes in 0-75 Amps and outputs 0-1 V. The hardware configuration is set to the 0-10V option and our cables are plugged into CM0 and I0V. Even when supplying the analog input pins with a constant voltage from a DC power source the readings would fluctuate between 0 and the value which was input.  When reading the CT's output with a multi meter there was a constant AC reading, so I believe the CT is working as intended. If we use the smoothing option it just averages everything out to a value just under half of what it should be.

[Gabriel Franco]

I suspect you´re using a CT with AC volts output.  Analog input is only DC, 0 ... 10 Vdc range, then you need a converter from AC Volt to DC Volt.

[Ausman]

Agree with Gabriel. 

Also, it is possible that you have damaged something by not looking into all the parameters in the first place before connecting AC to something that is DC.  This may account for the fluctuations you experience with the tester.  You should be using the final CT product in your testing, not something that is different.....it's not much of a durability test if it isn't the product you're going to be using. Finally, ensure that you have all the wiring as recommended in the install literature.

cheers, Aus

[Joe Tauser]

Please post the make and model of the CT.  A link to a data sheet would be even better.

Joe T.

[chand345]

The link to the first CT's data sheet is here:

https://www.crmagnetics.com/Assets/ProductPDFs/CR3100.pdf

Another CT we tried is here (this one requires a resistor to be put in parallel across the output).

https://datasheet.octopart.com/CR8410-1000-CR-Magnetics-datasheet-17019953.pdf

Although I think that was the case. These CT's only send a small AC signal back which could be the cause of the fluctuation .

Would you have any recommendations? could we use a rectifier possibly?  anything would be great.

Also, thanks for the help and patience on this post.

 

[chand345]

Do you know of any CT's that can read alternating current and maybe somehow outputs a constant rms value? thanks.

[Joe Tauser]

You need something with a DC output compatible with what the PLC is looking for.

These are the ones I use (full disclosure: and sell as a distributor)-

http://www.dwyer-inst.com/Product/ProcessControl/CurrentTransformers-Switches/SeriesCCT60-70

 

Joe T.