If you are an embedded hardware engineer who is into product designing, then you must be aware about the importance of understanding the power consumption by each and every part of your circuit in order to validate and optimize your circuit. Nordic’s Power Profiler Kit II is a device essential for validating and optimizing the performance of your embedded system. Apart from that it also helps you in deciding the battery or energy storage system and the PPK2 kit can tell you exactly about that. This device can accurately measure the energy consumption of your embedded prototypes, even the ones utilizing miniscule quantity of current.
In this article, I will tell you about the specifications, features, functionality of this board and also demonstrate you how to connect and use it to measure the power of your embedded system. I will also briefly talk about its comparison with other similar products in the market. So, without further ado, let’s get started and dive deeper into this product.
Nordic Semiconductor’s Power Profiler Kit II (PPK2) is an affordable and flexible tool which provides engineers capability to measure current as low as 200 nano amp all the way to 1Amps with resolution as high as 100nA for lower current. A special feature about this device is that it has both the Source meter mode and Ampere meter mode. In source mode, the PPK2 acts as a source which is capable of supplying voltage in the range of 0.8V to 5v with a maximum of 1Amp of current, i.e. it can act as a 5W power supply. This feature makes it capable of working as a standalone system for analyzing power consumption of your system.
Apart from the instantaneous current, it is capable of measuring average current over a period of time.
The company also offers an application called nRF Connect software to connect it with the PC which helps in analyzing and exporting the data for post-processing.
- Variable power supply voltage 0.8 V to 5.0 V
- Up to 1 A current measurement
- Source mode and ampere meter mode
- High resolution, down to 0.2uA
- Auto switch to 5 different measurement range for higher efficiency and better resolution.
- 100k sample/sec
- 8 pin digital port for digital tracing
- Real-time current measurement display
- Feature rich desktop application with a simple user interface.
- USB communication, enabling simple porting to other applications
- Desktop application for measurement analysis
- Export measurement data for post processing and analysis
What’s inside the box?
The device comes in a simple cardboard box with minimal graphics. The first thing you get in the box is the PPK2 placed inside an anti-static bag. Apart from that you get a 10-pin logic port cable and a 4-pin current measurement cable.
- Power Profiler Kit II board
- 10-pin logic port cable
- 4-pin current measurement cable
Coming to the PPK II
There are 2 USB female connector on the top side of the board., 1 is for transferring power as well as the data while the other connector is just for the power. USB connection for supplying extra power to the PPK2. Only needed in Source Meter mode (> 400 mA).
There is an on and off switch located at the center of the board.
In the bottom of the board, we have a 10 pin dupont wire connector and in the other corner we have a 4 pin dupont connector.
The 4-pin male connector is used for powering in the board and to give output power from the board. So, when using the board in the source mode, you need to provide it with external power and the first 2 pins will act as an input for your PPK2 while the next 2 pins will work as an output supplying power to your embedded system.
In the other side of the board, there is another set of 10 pins marked as Logic Port. It contains 8 digital pins along with the Vcc and ground pins. The PPK2 is capable of simultaneously measuring digital inputs from 8 different channels. It provides a low-end logic analyzer functionality.
Connector Description:
GND - Ground connection to DUT.
VOUT - Positive voltage output to DUT.
VIN - External power input. Only used for Ampere meter mode.
GND - Ground connection to DUT.
USB DATA/POWER - USB connection for power and communication with the PPK2.
USB POWER ONLY - USB connection for supplying extra power to the PPK2. Only needed in Source Meter mode (> 400 mA).
LOGIC PORT
VCC - VCC of DUT
GND - GND of DUT
D0–D7 - Digital input pins
How to use the Logic Port?
You can use your PPK2 as a low-end logic analyser. Suppose you designed a simple system that can measure temperature and humidity and atmospheric pressure, then you can connect 1 digital pin from logic analyzer to your microcontroller and pull the gpio’s high or low (depending on your code) to operate each sensor separately and measure the current consumption in each case. This method can help you optimize your system as well as help in calculation of your energy storage system.
How does PPK2 Measure Current?
The power profiler kit II has an analog to digital converter (ADC) to measure voltage drop across a series of fixed measurement resistors, the voltage drop is calculated by ohm’s law. The heart of the system is Nordic’s nRF52840 System on Chip(SoC). It uses USB Communication Device Class (CDC) and Abstract Control Model (ACM) which is supported by all the major OS, making it usable without installation of any extra driver. It features an automatic switching circuitry which can automatically change between 5 different measurement ranges to provide a very accurate output. The block diagram of the PPKII is shown below.
Installing the Power Profiler App
To start using your device, you need to have the power profiler app installed in your PC and to do that follow the steps mentioned below.
Install the nRF Connect app for desktop by downloading it from the company’s website.
Open the app and find the power profiler app in the list or alternatively, you can click on the search bar and type Power Profiler app and click install.
Now you can open the app and connect your PPK2 to start analyzing the power consumption.
Whenever a new update is available, an Update button becomes available just next to the click on the button and your app will be updated to the new version.
How to connect your nRF Connect software to the PC?
You require a USB cable to power the board as well as connect it to the PC of logging and displaying data. You need to install the nRF Connect software which you can download from the Nordic’s website. This software can be used on Windows, MacOS as well as on the Linux.
Measuring Modes of PPK II
The PPK II has 2 measuring modes, the Source Meter Mode and the Ampere Mode. To select a mode, you need to use the application. More details about both the modes are given below.
The figure below, taken from the official datasheet shows how we can connect a device with our PPK II. In the figure the PPK II is used with a nRF9160 development kit in a source meter mode.
Source Meter Mode:
When the device is being used in the Source Meter mode, the PPK II works like a power supply, powering the device under test (DUT). The voltage output can be varied between 0.8V to 5V and it can supply a max of 1A of current. In this mode, the USB power source has to supply 50mA for the PPK2 in addition to the max supply current consumption of the device under test.
Note: Incase you have to provide more than 600mA of power to Device Under Test (DUT), then you need to use both the USB simultaneously.
Ampere Meter Mode:
When the PPK II is working in Ampere meter mode, it works just like an ammeter and measured the current, in this case the nordic’s power profiler doesn’t supply any energy and the module to be tested needs to be powered from an external source.
The maximum current of device under test, in both the modes are given below:
Measurement Resolution and Accuracy:
The resolution tells us the smallest unit of current this device is capable of measuring. The resolution of PPK2 is given in the table below.
Accuracy plays an essential part of any measuring equipment. It tells the user how close the displayed values are to the actual value. The accuracy of PPK2 in different range is give in the table below.
Viewing Modes:
The power profiler App has 2 viewing mode - The data logger mode and the real time mode. The two modes provide detailed power consumption of a connected device.
Real-time view:
In this mode, the module work as an oscilloscope, showing the real time values of the power consumption.
Data Logger view:
This mode is basically used to monitor and analyze the power consumption over a period of time.
Advanced controls
The software allows you to enable few more features such as adjusting gain for individual ranges or switch on a spike filter, these features can be accessed by opening the advance control panel by clicking Ctrl+ALT+Shift+A
Testing the PPK II
To test the module, I have used 2 NodeMCUs, one is a brand-new device while the other one is a bit damaged, which causes a bit of heat generation thus wasting a power. We will connect both the device to see how much energy does the defective device consumes.
When connected to a brand new NodeMCU, it consumed an average current of 237 mA as shown in the image below.
When we connected the damaged NodeMCU, the average current consumption was around 360mA.
As expected, the damaged NodeMCU was wasting around 120mA of energy as heat, which makes it waste 35% power as heat.
Operating Parameter:
According to Nordic’s official datasheet, the board is meant to be used indoors. The operating parameters of the board is listed below in the table:
|
Item |
Description |
|
Indoor or outdoor use |
Indoor |
|
Altitude |
Up to 2000m |
|
Temperature |
5–40 °C |
|
Relative humidity |
80% max |
Alternate Tools
There are a lot of alternate tools for DC power profiling available in the market. Most of the tools for this application cost north of $500. Some of the most common power profiling tools are compared in the table below:
|
Device name |
Cost |
Voltage range |
Current range |
|
Power Profiler Kit II |
$89 |
0.8 – 5 V |
0-1A |
|
Joulescope |
$799 |
-1 – 15 V |
-1 – 3 A |
|
Otii |
$699 |
0.55 – 4.55 V |
0 – 3 A |
|
BattLab |
$99 |
1.2 – 4.5 V |
0 – 450 mA |
|
uCurrent Gold |
AU$ 89(ex. tax) |
2.7 – 5.5 V |
0 -1.25A |
Conclusion
The PPK2 is a great tool for measuring and analyzing power of your embedded system. It has a wide range with good resolution and a decent accuracy. The device has 2 modes and can work as s a power supply for low powered applications. For the cost of $89, it is a good purchase for anyone developing a battery powered device.
