T J SHARON

OMRON CJ2M-AD08V1 - AD data fluctuation

9 posts in this topic

HI, 

I am re-posting this thread as i did'nt  manage to solve. The AD conversion values are fluctuating during open circuit (refer to video).

And values remains stable once it is powered.My 8 AD channels are sharing  power supply. Refer to pic.

 

Appreciate all  help and suggestions.

 

thanks

capture.png

15faad186bf0b0124a0db59248b78c34.mp4

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Inputs going negative - below 4ma if you are using 4-20ma devices. The input devices need calibrating up or the analogue card calibrating down.

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1. Why are there switches (rectangle with a lever arm is a switch?) in an analog input circuit ?

2.  Are these 8 signals current signals or voltage signals?

3.  What are the field signal generators?   pure current through a variable resistance?   output of a transmitter?  

4.  What is an A/L screen?  If it's the cable shield, then connect it to chassis ground, not to the AI (-)

5.  The video appears to show some high count value toggling with the value 0.  Is that a correct interpretation?

Is that happening with the switches in the open state?

If the switches close, what happens?

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hi Dan, 

1) those are button switches in the control console.The reason added a switch to prevent someone accidently using potentiometer. 

2) these are voltage signals.

3) Pure voltage from PSU to the ADunit via push button and potentiometer 

4) Currently i don't have have any screens. Just copied from the manual for future use.   but fluctuation reduced after i connected A5 & B5 to 0V.

5) the values should be &0-4000 UINT. high count is only on open circuit condition. The values are accurate and stable at closed circuit.

capture.png

Capture1.PNG

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Apparently a high value during the open circuit state is not acceptable?  What is acceptable, zero volts?

Your AI will show 0 volts when shorted.

What about using a SPDT switch where the terminal shown as the open switch state connects to the AI (+) input, so that when the switch is open the AI (+) is shorted to V (-), but when switch toggles the AI reads the pot voltage drop as shown?

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Hi Dan, 

Thanks for the reply.

Yes, Values in open circuit fluctuates as the previous video. 0v is acceptable

SPDT as show in the pic? 

capture.png

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That will certainly work but now you have to activate 2 switches.

13/14 is SPST.  If it were SPDT with another terminal for the open position (as shown), say 13/14/15 then with only one activation you could ground the input through the unpowered 10K pot which is effectively a grounded input which should give you zero volts (I'd try it just to make sure that is doesn't draw a bias current somewhere and give you an offset).

open-circuit-voltage-AI-goes-to-max-scal

 

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