Posted 22 Nov 2019 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 15faad186bf0b0124a0db59248b78c34.mp4 Share this post Link to post Share on other sites
Posted 22 Nov 2019 Inputs going negative - below 4ma if you are using 4-20ma devices. The input devices need calibrating up or the analogue card calibrating down. Share this post Link to post Share on other sites
Posted 25 Nov 2019 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? Share this post Link to post Share on other sites
Posted 26 Nov 2019 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. Share this post Link to post Share on other sites
Posted 26 Nov 2019 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? Share this post Link to post Share on other sites
Posted 27 Nov 2019 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? Share this post Link to post Share on other sites
Posted 27 Nov 2019 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). Share this post Link to post Share on other sites
Posted 28 Nov 2019 Hi Dan, Thanks for the reply. I will try as u said. Share this post Link to post Share on other sites