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Table of Contents
Current Measurement
Nordic Power Profiler Kit II
Limits
- Max V: 5.5V
- Max I (measured): 1A
- Max I (sourced): 600mA
Accuracy
- < 50mA: ± 10% and ± 2% offset
- >= 50mA: ± 15% offset ± 5%
Qs
- Is it robust to output overcurrent or overvoltage?
- What does LED mean?
There is a third party python API: https://github.com/IRNAS/ppk2-api-python
Forum post about using it: https://community.element14.com/technologies/test-and-measurement/b/blog/posts/nordic-power-profiler-kit-ii-python-api
ACS758
Suitable for high current, high or low side, measurement where isolation is needed. Noise limits low current performance.
- Hall effect
- Isolated: 450V rms working voltage or higher, depending on standard.
- ~100uR conductor
- 3.0 - 5.5V supply
- 120kHz
- 10mV noise typical, with 10nF output filter. Corresponds to 0.25A.
- +-35mV offset
- 2% typ total error
- Zero current output is half Vcc.
https://www.allegromicro.com/-/media/files/datasheets/acs758-datasheet.pdf
LCB-050B variant: +-50A, 40mV/A typ. Ratiometric though - I think that is 40mV at 5V and changes with Vcc.
There are higher current variants.
Module
Purple Aliexpress module also has a TLC2272 opamp as a buffer after an RC filter. Sensor output is high impedance.
https://www.ti.com/lit/ds/symlink/tlc2272.pdf
- Opamp supply: +-2.2 to +-8V
- Input recommended max Vdd - 1.5. At 5V in, that is 3.5V.
- ACS758 will put out 4.5V with that supply and 50A measured.
This looks like an unsuitable choice of amp for general use.
Module pinout:
- Vcc: 3.3V or 5V ok. For 50A it wants to put out Vcc/2 + 2V, so will need at least 4V.
- Out1: Output of RC filter.
- Out 2: RC filter through buffer amp. Probably want to just use this one.