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121GW: Shunt Resistors used in Current Measurements

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JDW:
What are the SHUNT RESISTORS used in the 121GW for each Current Measurement Range?

For example, when using my µCurrent Gold, I know the following to be true...

* 0-1250 nA Range (10kΩ 0.1%): 10μV/nA

* 0-1250 µA Range (10Ω 0.1%): 10μV/µA

* 0-1250 mA Range (10mΩ 0.5%): nominal 70μV/mA
And when using my Fluke 8845A benchtop meter, the following is true (click attachment)...

J-R:
Have a look at page 18 of the user manual: https://www.eevblog.com/wp-content/uploads/2017/11/121GW-Manual-5.pdf

JDW:

--- Quote from: J-R on February 19, 2023, 12:31:11 pm ---Have a look at page 18 of the user manual: https://www.eevblog.com/wp-content/uploads/2017/11/121GW-Manual-5.pdf

--- End quote ---

I just did.  Nowhere on page 18 is there any specific mention of the Shunt Resistance Values.

If you know the exact resistance values in Ohms, please post that in your reply.

Thank you.

Gyro:
You can very easily derive it from the burden voltage (voltage/current) and ohms law.

JDW:

--- Quote from: Gyro on February 19, 2023, 12:44:38 pm ---You can very easily derive it from the burden voltage (voltage/current) and ohms law.

--- End quote ---

Nobody likes to calculate when a nice graphic plainly and quickly gives all the answers, so I have done that work for others who read through this thread in the future, as per the attachment I created below.

However, the 121GW Schematic shows the actual shunts to be:

R33: 100Ω
R43: 1Ω

And it appears that Fusing also affects the actual shunt resistance too, which in turn impacts the Burden Voltage.

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