Fx2424 analog port read issue

[cch1955]

I have a very strange ADC issue on a Fx2424

With a simple ADC test program (attached) I show no ADC inputs when in online monitor mode on the lines 5 and 6 as I would expect ( they show DC voltage on the inputs with DVM of between 1.5 to 2.5 volts from attached pots). I show a ADC value of 4091 on line 1 with nothing connected and DVM voltage shows no voltage at the input. The 5 volt reference voltage supply is not being pulled down by the pots.

Have run this on two different Fx2424 with same result.

Disconnected everything from the PLC except the analog input daughter board ( and I swapped those also) Ethernet and 24VDC coming in clean. If remove the analog daughter board analog 1 register stays at 4091 when watch with online monitor mode.

I suspect I have developed some kind of software/firmware version issue.

Now have:

Tri version 7.11 build 04

Java 8 up to date

Swapped my router and cables, same result.

Scoped the 24VDC – nice and clean and 24 volts

Tried different scan times for the read, no difference.

When I run online watch I see nothing for ADC inputs 5 and 6, 4091 for ADC line 1 and

The variables assigned for the ADC reads show nothing except input 1 which shows 4091

What am I missing???

[cch1955]

Found the problem. It was an analog input ground wiring issue. Fixed that and it responds as it should.

[support]

Thank you for the updates. Our tech support team has also emailed you some suggestions on the possible causes of what you observed but we are glad that in the end you found out that it was a simple ground wiring issue.