AD71056 has some questionable operation.
Test setup: a relay connects a load, then the system waits a few seconds (MCU counts the pulses from AD); then the relay disconnects the load, system waits awhile and cycle restarts. AD71056 operates in high frequency output mode (which is 2 KHz). The relay is between AD71056 and the load, that is, AD71056 itself is constantly powered.
In this setup AD71056 periodically reads a doubled value, for example
[2491s] Test #415: 184 (OK)
[2497s] Test #416: 186 (OK)
[2503s] Test #417: 382 (OK) <<-- doubled impulse count!!!
[2509s] Test #418: 191 (OK)
[2515s] Test #419: 189 (OK)
Can it be that the part itself returns from no load incorrectly?
Can you please examine the inputs using a scope (the scope needs to be isolated, no earth ground) and also please include the pulses (rate of the pulses). There might be a debouncing on the relay which does not switch off cleanly. Relays are inherently noisy due to debounce.
Hi, thank you for your idea, we will check this in the lab and try to get the scope.
Hi, it looks that this is the right way to understand the issue. We can't give you the scope picture, since we don't have a device that can capture data at high voltage. However with some noise reduction workaround we eliminated the issue.