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current_measurement

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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

INA3221

Aliexpress devboard notes

  • Rs: 2W, 1%, 100mOhm.
  • Solder jumpers connect a chosen pin to A0 to set I2C address.
  • Voltages are measured from -ve sense pins.
  • VS: Supply voltage
  • VPU: Pullup voltage for power valid function
  • TC: Timing control alert. Used for power sequencing test.
  • Board has 10k i2c pullups

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.
current_measurement.1712523247.txt.gz · Last modified: 2024/04/07 20:54 by river

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