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--- current_measurement [2024/04/07 01:40] – river
+++ current_measurement [2025/04/27 20:17] (current) – river
@@ Line 3: / Line 3: @@
 ===== Nordic Power Profiler Kit II =====
-[[https://infocenter.nordicsemi.com/pdf/PPK2_User_Guide_v1.0.1.pdf|Manual]]
+{{ :ppk2_user_guide_v1.0.1.pdf | Manual}}
 == Limits ==
@@ Line 12: / Line 12: @@
 == Accuracy ==
+Specified:
   * < 50mA: ± 10% and ± 2% offset
   * >= 50mA: ± 15% offset ± 5%
+At points I checked, it was within 1.5%.
 == Qs ==
@@ Line 20: / Line 24: @@
   * Is it robust to output overcurrent or overvoltage?
   * What does LED mean?
+== Usage ==
+In ammeter mode, it requires a ground connection. Only connecting power in and out will cause weird / oscillating or maybe just slightly wrong readings.
+It also needs enough voltage to give a proper reading. Low voltage from the input to ground can cause readings that are a bit off.
+USB is not isolated. Ground is shared with power output / target device.
+== Log ==
+April 2024
+I connected it to a faulty device which drew too much current. The ppk2 firmware crashed as soon as power was switched on, and the device disconnected from USB. It seems like it does not have any overcurrent protection. A forum post said the sense resistors were damaged by overcurrent, and another suggested that they could be partly damaged and ruin the accuracy. Can it be recalibrated?
+April 2025
+Checked readings against good multimeters. It seems it is still in spec. Within about 1.5% for values I checked.
+== Misc ==
 There is a third party python API: [[https://github.com/IRNAS/ppk2-api-python]]
@@ Line 31: / Line 55: @@
   * 350 μA consumption (quiescent though - working unspecified)
   * 13 bit ADC. 40uV resolution on current sense.
-  * VSHUNT Shunt voltage input –163.84 to 163.8 mV. Quite limitng.
+  * VSHUNT Shunt voltage input –163.84 to 163.8 mV. Quite limiting.
   * [[https://www.ti.com/tool/download/CS-AMPLIFIER-ERROR-TOOL]]
   * [[https://www.ti.com/lit/ds/symlink/ina3221.pdf]]
@@ Line 46: / Line 70: @@
   * Board has 10k i2c pullups
+mR shunts gives max measurable current of 1638mA. I think it shouldn't be damaged with more though - abs max values are all much higher.
+{{:ina3221_board.png?600|}}
 ===== ACS758 =====