Measurement ranges and switch levels

RE: Measurement ranges and switch levels

Jared — Thu, 22 Dec 2022 14:36:46 GMT

Hi,

You can adjust the gain by pressing ALT-SHIFT-CTRL-A in the nRF Connect Desktop app but this is not recommended for normal usage. The resistors in the measurement resolution isn't directly corresponding to a specific resistor in the schematic, and you are not meant to modify them directly. Instead you can configure the gain by adding an offset to the gain settings. For example if you notice that you have an offset when you measure current in the 200 nA to 50 µA range, then you can configure Range 1 in the gain settings. Only using one level without switching is not supported as far as I know.

regards

Jared

RE: Measurement ranges and switch levels

Maryam Shadi — Tue, 20 Dec 2022 16:07:36 GMT

Hi,

I appreciate your response.

Based on the schematic there are 4 paths that changes the value of the resistor baes on the current value to measure the current. I found that the R42 parallels with R41 is used when the value of the current measurement is around 5m A~ 50 mA. I would like to map these resistors consisting of R42,R46,R50,R54 with the measurement resolution table. Maybe the name of the R1_Resol and R2_Resol , so on should be change by R42,R46,R50,R54 in order to understand which resistors used in each current range.

Could you help me to understand which resistors is used for different current ranges?

And, one thing more, how can modify theses switch manually? Can I fixed this switch to SW4 ?

Best Regards,

Maryam

RE: Measurement ranges and switch levels

helsing — Tue, 13 Dec 2022 15:27:29 GMT

I believe the resistor you are asking for is R42, which is 110 Ohms.

The schematics for PPK2 can be found on our website.

The PPK2 is selecting automatically between the resistors. However, you could try to modify the boards by manipulating SW1, SW2, SW3, SW4 to turn on and off the loads.

Here is a description of the Measurement system from the PPK2 user guide:

The Power Profiler Kit II (PPK2) is driven by the nRF52840 System on Chip (SoC), which uses its analog-to-digital converter (ADC) to measure a voltage drop over a series of measurement resistors. Resistor values are used to calculate the power consumption. The PPK2 has five different measurement ranges, which are managed by an automatic switch circuitry.

The Measurement accuracy is specified for the various ranges:

Name	Range	Typ	Description
R1_Accuracy	100 nA–50 µA	± 10%	Readout on average value
R1_Offset	100 nA–50 µA	± 2%
R2_Accuracy	50 µA–500 µA	± 10%	Readout on average value
R2_Offset	50 µA–500 µA	± 2%
R3_Accuracy	500 µA–5 mA	± 10%	Readout on average value
R3_Offset	500 µA–5 mA	± 2%
R4_Accuracy	5 mA–50 mA	± 10%	Readout on average value
R4_Offset	5 mA–50 mA	± 2%
R5_Accuracy	50 mA–1000 mA	± 15%	Readout on average value
R5_Offset	50 mA–1000 mA	± 5%

Table 1. Measurement accuracy

Does this answer your questions?

RE: Measurement ranges and switch levels

Maryam Shadi — Mon, 12 Dec 2022 08:20:32 GMT

Hi Hakon,

Very mrch thanks.

Best Regards,

Maryam

RE: Measurement ranges and switch levels

helsing — Fri, 09 Dec 2022 14:49:44 GMT

Hi Maryam,

Thank you for your request. We will look this up and get back to you.

Best regards,

Håkon