Range adjustment

Started by GJK, October 02, 2020, 05:28:55 PM

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GJK

October 02, 2020, 05:28:55 PM
Nice product
Most of the currents I wish to measure are in the 1-100mA.
Given the equipment I have the resolution is not that great

Can I just change the resistor on the mA from 0.01ohm to 0.1ohm.
So that I can get 10mV/1mA
Does it need to be re-calibrated?

thx

Felix

#1
October 02, 2020, 05:34:02 PM
Haven't tried something like that. Not sure I can advise to do that or not.
You risk overloading the amps if you put anything more than 300mA at the input, if you ever forget.
The OLED would obviously read 10x more than the actual value.
Calibration is more about the ADC linearity than the accuracy of the shunts which can be independently off from each other. So no to recalibrate.

But to circle back to your statement - "given the equipment I have the resolution is not that great" do you mean the DMM that you read the CR's raw output with?
Even a basic multimeter should give you enough resolution. Or maybe I'm not understanding this properly?

GJK

#2
October 05, 2020, 07:46:18 AM
Felix

Thanks for the reply.

I am measuring a low power IoT device.  Therefore the Tx signal is about 50mA, but sleep currents are in the 20uA range.  So the range of the uA/nA is fine but the mA is a problem.  I am using a PC Scope in datalogger mode so my resolution is only 10bits. 

Back to my question is there any reason I can't just change the resistor for the mA range.  What is the package size
Also, what is the part number for the green terminal block.  I would like to pick up a few more.

thx

Felix

#3
October 05, 2020, 09:31:13 AM Last Edit: October 05, 2020, 09:50:05 AM by Felix
All my thoughts I had on the change I put in my first reply.
I can't really give a definite answer to that question because I haven't designed the CR to work with a 100mOhm shunt.
Any changes to the CR are at the owner's own risk. I am not able to give warranties or back such experimental changes.

Here's the green terminal: https://www.digikey.com/product-detail/en/1792863/277-2518-ND/

Felix

#5
October 05, 2020, 11:10:19 AM
2512 footprint
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