PM8240 Issue of Digital Input Signal

[mimi1002]

Hi everyone,

I would like to ask for your help due to a problem that occurred during the digital input signal test of PM8240.

 -CB Status, OCR, and OCGR signals were sequentially connected to the onboard digital input terminals S1, S2, and S3 of the PM8240 and an external power supply was used for DC24V power.

 -During the S1 terminal test, the counter of the S2 and S3 terminals rises, and the S1 terminals also rise by two or more.

 -Therefore, the debounce setting of the digital input module was changed to 1 second, and the test was completed normally.

 -Since then, the counter of the s1 terminal has risen even though 3 out of 15 products have not been tested. S2, S3 terminals clear.

Q1) Is there anything that causes the above symptoms, or is there anything you suspect, or what you want to check?

One test was that the counter did not rise when the DC16V power of the digital input option module was connected.

It is presumed to be caused by electrical noise during the signal test process, but it is not clear. If anyone knows the content well, I would appreciate it if you could let me know.

Thansk a lot.

Best Regards.

[Charles_Murison]

Hello @mimi1002 ,

May be helpful if you could provide a wiring diagram to show how the system was connected.

Regards,

Charles

[mimi1002]

Hello @Charles_Murison 

This is wiring diagram.

As I said, the DC24v power source used an external power supply.

[Charles_Murison]

Hello @mimi1002 ,

Wiring looks good, as to why you are seeing that behavior is strange. To troubleshoot this likely would need to measure the inputs to the meter to see if signals match what meter is reporting.

Regards,

Charles

[DanL · Accepted solution]

This looks great to me assuming:
1) the "24v" supply is a DC voltage source capable of supplying >= 10mA DC (and source impedance is << 1000 ohms)

2) the 24v DC supply does not have significant common-mode (voltage with respect to ground) AC voltage. If the supply is ground-referenced or properly isolated this is not an issue. 

3) the 3 signals "CB Status, OCR, and OCGR" are simple low impedance and dry contact switches as shown.

[Charles_Murison]

Hello @mimi1002 ,

Did you still need help with this topic?

Regards,

Charles