Author Topic: Current Ranger with DMM [SOLVED]  (Read 369 times)

alexsh1

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Current Ranger with DMM [SOLVED]
« on: November 18, 2018, 01:57:21 PM »
Hi Felix,

I wonder if you could replicate this.
My setup: a node is connected to the CurrentRanger with DMM.
I am sampling a sleeping node in autoranging mode with the CurrentRanger.
As soon as the node wakes up, my DMM goes out of range and autoranging on the CurrentRanger does not work until I switch the scale up on my DMM from mV to V.
I think this problem is only if autoranging has to go up (from nA to uA or to mA).

This problem is only for the CurrentRanger and DMM.
Without DMM it works just fine.
« Last Edit: November 20, 2018, 04:31:44 PM by Felix »

Felix

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Re: Current Ranger with DMM
« Reply #1 on: November 19, 2018, 04:06:09 PM »
I think your problem is that you're trying to stay in the mV range always on your DMM.
It will go out of range when the CR ranges, that's expected. That's how the CR detects an overload, before it can range up.
Can you use the high resolution mode in V range (assuming your DMM has one)?

alexsh1

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Re: Current Ranger with DMM
« Reply #2 on: November 20, 2018, 08:35:08 AM »
I think your problem is that you're trying to stay in the mV range always on your DMM.
It will go out of range when the CR ranges, that's expected. That's how the CR detects an overload, before it can range up.
Can you use the high resolution mode in V range (assuming your DMM has one)?

With a handheld DMM even with high resolution, I am still loosing a few digits in V position vs mV position. I think the inconvenience here is that autoranging is not working until I manual put the DMM into Volts and then immoderately back in mV. Ranging down does not have this issue.

Felix

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Re: Current Ranger with DMM
« Reply #3 on: November 20, 2018, 10:22:29 AM »
If the up-ranging produces a mV reading that is within your DMM's mV range, I would expect the DMM to readjust after an overload
It sounds like your DMM cannot readjust in mV after an overload?

Quote
Ranging down does not have this issue.
That is expected, it's because down-ranging goes to 0 rather than an overload. So when the ADC detects a very close to 0 reading, it down ranges. As opposed to an overload which up-ranges.

alexsh1

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[SOLVED] Re: Current Ranger with DMM
« Reply #4 on: November 20, 2018, 02:46:30 PM »
If the up-ranging produces a mV reading that is within your DMM's mV range, I would expect the DMM to readjust after an overload
It sounds like your DMM cannot readjust in mV after an overload?

You are right.
I have just tried Brymen bm869s and it works with autoranging up.
It seems that it is related to my new 121GW only.

Felix

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Re: Current Ranger with DMM [SOLVED]
« Reply #5 on: November 20, 2018, 04:32:31 PM »
Great, thanks for the update!