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02-21-2021 09:47 PM

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Hi,

I am having problems on understanding the computation for PXIe-6570 Force/Measure Current Accuracy.

What comes next after finding the zone (step 6)?

Can anyone give me an example of the computation?

Thanks!

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Solution

Accepted by PatriciaM

02-22-2021 06:25 PM - edited 02-22-2021 07:07 PM

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Let me show you an example for calculating accuracy,

Steps

- FI = 1.5mA
- Using 2mA as the best range
- % Force current range = (1.5m / 2m)*100 = +75%
- Assume my impedance is 1k Ohm, Voltage Required = 1k * 1.5m = 1.5V
- Plotting the 1.5V, +75% in the Figure3, the point lies in the grey area which is designated as zone 1
- Looking at Table1, it states that +-1% for Zone1 irrespective of range
- Though not explicitly stated, you calculate the accuracy as you typically do for any measurement or value in engineering, apply +-1% to +-2mA range, now it becomes +-40uA because +-2mA constitutes 4mA total range.

Hope step 7 clarifies your question about how to apply +-1% to get the accuracy number.

Alternatively, if my impedance was 100 ohm and force current was -1.5mA, the voltage required becomes 150mV. Now, the 150mV, -75% lies outside zone1 in the graph and hence there is no warranted accuracy specification (as mentioned in step5)

02-23-2021 07:44 PM

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It makes so much more sense now.

Thank you!