Power/Current Consumption Measurement with DC Power Analyzer

[omergokmen]

I am trying to measure current consumption with different setups on nrf52dk_52832 such as humudity, temperature sensors etc.

To do that i plug dc power analyzer to external supply pins after cut sb9 and soldering sb12. My main assumption is if dc power analyzer gives 3V to nrf52dk and i run with this, i should see correct results for current consumption analysis.

But it gives approx. 23mA average and i can not decrease it. Even in idle(by erasing memory) it is 28mA average with this measurement method. 

My questions are:

1- Is my measurement method wrong?

2- If so, or even if not, What are other ways to measure average current/power consumption?

3- How can i decrease average current/power consumption to make my battery last longer?

4- Also, What is power cycling in "After programming the nRF52832 SoC, the USB must be disconnected and the DK power cycled to reset the debugger chip before current measurement."?

Thanks in advance.

[Hieu]

Hi omergokmen,

1- Is my measurement method wrong?

2- If so, or even if not, What are other ways to measure average current/power consumption?

It depends on what you are trying to measure.

As you plug it in the External Supply port, you are powering the entire nRF52 DK. That will include things such as the Interface MCU circuit and IC not relevant to the applications. Is this what you are trying to measure?

If you want to measure only the nRF52832, then please plug the cable following this guide: Measuring current in Source Meter mode.
The image there can appear a little small on the page. Please open the image in a new tab and zoom in.

3- How can i decrease average current/power consumption to make my battery last longer?

We have a few guides on this:

https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/optimizing-power-on-nrf52-designs
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/test_and_optimize/optimizing/power.html
https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/optimizing-power-on-nrf53-designs (the guide is for the nRF5340, but many tips are applicable to the nRF52832).

4- Also, What is power cycling in "After programming the nRF52832 SoC, the USB must be disconnected and the DK power cycled to reset the debugger chip before current measurement."?

It just means turn it off and on again. You can cut off the power with the switch or cut off/turn on power from the Power Profiler tool.

Hieu

P.s: We are entering the summer vacation period here and are currently understaffed. Therefore, please excuse some delays in responses. Our apologies for the inconveniences.

[omergokmen]

Thanks for your detailed answer. 

I will follow those guides for my DK.

But there is something unclear to me.


Now i am using nrf52dk_52832 with humudity sensor sht20. This is just for development process. In the near future i will produce PCB design of my setup(nrd52832 chip, sht20, ble antenna etc.). 

For now I want to see my improvements on power consumption with correct measurements on DK. But when i get my PCB i will also measure power consumption on that.

For now I measured in two ways:

1- plug dc power analyzer to external supply pins of DK with 3V, then do analyzing for some time then observe results such as average current/power consumption. (approx. 25mA)

2- plug dc source to external supply pins of DK with 3V,and plug amperemeter to current measurement pins. then observe current value calculated. (approx. 1.5 mA)

What equipments do i need to get reaasonable measurements?

* I have DC power analyzer and amperemeter. And I want to measure average current consumption(power consumption) with my equipments. Can i do it by plugging required connections according to prepared DK part in your document.

Also, while measuring on DK, will results be reasonable, such as DK has different peripherals, mcu interface etc. and i want to measure only my setup which also will be on PCB not unused things in my use case?

I watched the video of measurement with PPK2, the average current measured in the video was approx. 3.5mA which seems quite high.

If this will not give a reasoanble results for my application lifespan with battery, is the only way of getting correct lifespan of my application waiting for my PCB(as simplified DK)?

Since till now, I have only measured around 1.5mA which is quite high for my application and make me skeptical about my measurement method. Why is my result is high? -> Since I have a battery 590mAh, and if i divide 590 mAh with 1.5mA the result is 16 days lifespan for my application which is low. 


Lastly, if measurement with these scenarios give correct observations , which equipment is suitable for me ? (PPK2 vs my measurement equipment.)

If not, how can i estimate lifespan of my application? and how can i observe results of my power management improvements on DK?


sorry for my long question,

Thanks in advance.

[Hieu]

omergokmen said:

What equipments do i need to get reaasonable measurements?

* I have DC power analyzer and amperemeter. And I want to measure average current consumption(power consumption) with my equipments. Can i do it by plugging required connections according to prepared DK part in your document.

Yes, you can use the power analyzer or the amperemeter to measure following the guide I linked. 

The ampere meter can only give you the average instantaneous current of the setup, so perhaps that is the least helpful method. However, you can do so by following the Measuring current in Ampere Meter mode guide, replacing the PPK2 with the ampere meter instead.

It seems your power analyzer is also more than sufficient for the job. You can similarly use it with the Measuring current in Source Meter mode guide.

omergokmen said:

I watched the video of measurement with PPK2, the average current measured in the video was approx. 3.5mA which seems quite high.

I am not sure which video you are referring to here, but at 3.5mA, the device might be running some work, such as actively scanning on Bluetooth Low Energy, or running several high-power peripherals such as TIMER at high clock. 

As a sensor reading device, there are certainly designs to keep the nRF SoC current consumption low, under 1mA, or even in the uA range, depending on the specific requirements.

You can find reference current consumption of the nRF52832 documented here: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/pmu.html?cp=5_2_0_16_0#unique_1667566419.

omergokmen said:

For now I measured in two ways:

1- plug dc power analyzer to external supply pins of DK with 3V, then do analyzing for some time then observe results such as average current/power consumption. (approx. 25mA)

2- plug dc source to external supply pins of DK with 3V,and plug amperemeter to current measurement pins. then observe current value calculated. (approx. 1.5 mA)

omergokmen said:

Also, while measuring on DK, will results be reasonable, such as DK has different peripherals, mcu interface etc. and i want to measure only my setup which also will be on PCB not unused things in my use case?

I think you are referring to your measuring setup #1 with this question. The measurement will not be a good reflection of your final PCB setup then. 

Setup #2, following the guides I have linked, is going to give you only the SoC current draw. For the whole product consumption, you could include your sensors into the setup for better measurements, or you could estimate the sensor current draw based on their datasheet.

omergokmen said:

Lastly, if measurement with these scenarios give correct observations , which equipment is suitable for me ? (PPK2 vs my measurement equipment.)

If not, how can i estimate lifespan of my application? and how can i observe results of my power management improvements on DK?

As noted at the beginning, your power analyzer should be sufficient. I think it will be better than most estimation methods.

We do provide a tool call the Online Power Profiler (actually linked up on the DevZone header banner), which help with estimation, but with a focus on the consumption of the radio and how the SoC is powered and how clock sources are provided.