Posted Mon, 17 Oct 2022 02:24:13 GMT by Robert Liang
Hi, experts.

I have searched a lot, but no result.

I want to achieve periodically auto-zeroing using the trigger model every two seconds. That is because I have tested that the 'auto-zero on' configuration clearly lower the data output rate. To achieve the balance of offset and data rate, I have to reduce the frequency of auto-zero but not close it.

I found there's no block in the 'trigger model' is about the auto-zero configurations, but some blocks for moving the 'configuration lists'. So currently I set two configuration lists, one with AZERO on, another off. For every two seconds, I change configuration from OFF to ON and then to OFF immediately to emulate 'AZERO once' function. This ON-OFF-ON switching will take 0.7 seconds as I tested.

My questions are:
1. I'm not sure that this method can work, and is there easier or more elegant way to achieve that?
2. My DC measurement for one time will last for at least 500 seconds. If I have to choose AZERO ON or AZERO OFF, which is better on precision?

Thank you very much.
Posted Tue, 18 Oct 2022 00:27:28 GMT by C, Andrea
Do you feel the auto zero needs updated within the 500 second measurement time?  Do you think the instrument is drifting within the 500 seconds?  Is it fully warmed up (1 hr)?
How much drift are you seeing?

Auto zero updates every 2 seconds does not seem likely to give benefit.

If no need to update so frequently, I would just call the auto zero with setting once to force the update then.
Next command to trigger init the 500 second acquisition.
Posted Tue, 18 Oct 2022 01:32:38 GMT by Robert Liang
Thanks for your answer!

It seems that the auto-zero once remote command will abort the trigger model. Actually my trigger model is like this: Wait for ext trigger -> Acquisition 500s -> Wait for ext trigger -> Acquisition 500s -> ... So except for the beginning, no other time that I could insert the AZERO once command. Although I'm still in the designing step, I'm afraid that it will drift during the whole measurement progress.

At least I think the support of auto-zero once in trigger model is necessary, but as I known it doesn't.

So please tell me if this instrument will update its autozero value if I switch the AZERO configuration from OFF to ON then to OFF by moving the configuration list in trigger model? Will it work? 

Thanks again.
Posted Tue, 18 Oct 2022 15:25:30 GMT by McKinney, Ty
The only option if you want to use autozero sometimes, but not all of the time during one 500s interval is to swap between config lists as you had mentioned before - I agree with Andrea that every 2s could possibly be too often and will lead to extra time being added.

Swapping config lists seems to work - we set up a trigger model that recalls a config list with azero ON, take 10 readings, switches to azero OFF, takes another 10 readings, and repeats. The resulting data shows that when azero is ON the readings take longer than when azero is OFF. You also would have to consider the time it takes to swap between the config lists. When the swap between azero OFF and ON is performed, the instrument will refresh its reference measurement each time.
Overall consider if the timing delay incurred by the settings swap via various config lists is worth the time saved by not using a zero all of the time.

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