MicroAmp-Meter is a current measurement tool featuring auto-ranging, Wi-Fi current profiling, SD card logging options, and more. It is a portable current meter that can record and profile the current consumption of devices in real-time. It has an automatic shunt-switching mechanism that enables it to measure the dynamic range of current levels ranging from 1uA to 1Amp. MicroAmp-Meter has Wi-Fi and an inbuilt Websocket server which provides an application in the web browser to display and record the current consumption in graphical form. It can also log current and other parameters on a micro SD Card for more than 12 hours.

Feature Highlights


The heart of the MicroAmp-Meter consists of a precision Current-Sense Amplifier INA190, three high precision shunts (30mΩ, 68mΩ, 30Ω), and 12bit ADC BU79100G for high-speed analog sensing. The shunt-switching topology is based on David Jones's design EEVblog #929 - Designing A Better Multimeter.
The brain of the MicroAmp-Meter is ESP32 running at 80Mhz. The used variant of ESP32 has two physical cores. Each core is pinned to a separate task in RTOS. The primary core of ESP32 is responsible for reading analog data from external ADC, calculating current, and switching shunts accordingly. Dedicating the physical core to shunt switching makes the process happen in about 200 microseconds. A secondary core is responsible for handling LCD, Voltage, Battery SOC, SD Card, and Wi-Fi functionalities.


MicroAmp-Meter is calibrated to the high precision voltage reference LDO output during flashing. The calibration values are stored in the EEPROM of the MicroAmp-Meter. These values are loaded from the EEPROM during the startup of the software and all readings are compensated accordingly.


Display Parameters

The description of the parameters of the main display page is given below:

Wi-Fi Mode

Wi-Fi mode is the main feature of the MicroAmo-Meter that provides an application to visualize current readings and other parameters over the web browser at a high speed of 4000 samples/second. The webpage application code resides inside the memory of MicroAmo-Meter. MicroAmp-Meter and web browser both need to be connected to the same Wi-Fi network. No internet connection or installation of software is required. For more details visit the section How To Use.

SD Card Logging Mode

SD card logging feature is useful to measure the current performance of a device over a long run. For more details visit the section How To Use. This feature logs the following parameters in the SD card over a time interval of 1 second:
TIP: LCD backlight consumes almost 40% of the total device current. Turning off the backlight during logging can drastically increase logging time.

Output Control

The output control feature provides access to disconnect the source from the load. This feature is controlled by a dedicated button switching the DUT on and off. LED is also attached to represent the state of the output.

Brightness Control

The brightness of the LCD is adjustable by button. This feature is useful to turn OFF the LCD backlight to save power during SD card logging mode. LCD has 3 brightness levels.

Overvoltage PROTECTION

The hardware protection circuit for overvoltage is used to clamp the input to the range of the ADC. In this case, the Schottky diodes are chosen for their low forward voltage drop. The Schottky diodes are connected to the ground and a 3.3 V system rail capable of sinking current. The series resistor after the Schottky diodes also helps limit the current into the ADC. There is also indication on LCD and Buzzer for measured voltage over range.

Overcurrent PROTECTION

The Overcurrent/Short protection is handled by software. MicroAmp-Meter automatically turns off output if the current exceeds over 1000mA. The feature is implemented with the highest software priority to execute the routine in less than 150us.

How to Use


Create a wifi.txt file in the root of the SD card. In the wifi.txt file, enter the SSID of your Wi-Fi in the first line and then enter a password in the second line. Then Insert the SD card in the MicroAmp-Meter.
Click the Wi-Fi Mode button. MicroAmp-Meter will connect to Wi-Fi and display the IP address on the screen.
Enter the IP address in the browser. Make sure the device is on the same network as of MicroAmp-Meter. The webpage will display the Current Profiler application.
Tip: The graph has an interactive Zoom/Drag feature. To zoom along only one axis place the cursor over the corresponding axis and then use the wheel/trackpad to zoom in/out without pressing a mouse button.