Note: Specification-wise, this is a drop-in replacement for my USB type-C power meter

Hey, wait a minute - there are much cheaper USB power meters on the market! What makes yours so special? Well, it's actually accurate.

You see - most USB power meters have measurement errors of 5% or more - and they often only display 3 significant digits. This is of course fine for just checking roughly how much power something is drawing, but for accurate energy measurements (e.g. debugging mobile apps, seeing how much power they draw over a longer period of time) you have to use tools that have well-defined accuracy specifications. This is your tool.

Even if you don't necessarily want to measure USB devices, you can use it for anything else, as long as the voltage stays between 4.1 and 20V. I have a useful little adapter board to tie this product to a removable terminal block.

If you want to use this product as a nice development board for the ATSAMD09D14A (with a snazzy OLED and some decent analog frontend circuitry), you can additionally buy the SWD to ribbon converter ($5 add-on) so you can use your Segger J-Link or other SWD debugger to program and debug the microcontroller on this board. Binaries of the default firmware are available.

Why did you make it?

This is a USB type-A modification of my USB type-C power meter.

Specifications

• -5 to +5A current measurements
• 2.5 Hz refresh rate
• Shows on-time since last reset (up to 99 days 23h59m59s)
• 4.1-25V voltage measurements (accuracy only guaranteed up to 20V)
• Measures current (A) with 100µA resolution
• Measures voltage with 100µV resolution up to 9.9999V, then 1mV up to 25.000V
• Calculates power (100µW resolution, up to 125.00W)
• Accumulates energy (100µWh resolution, accumulates up to 5000.0Wh with 0.1Wh resolution)
• Accumulates charge (100µAh resolution, accumulates up to 500.00Ah with 10mAh resolution)
• Shows maximum voltage variation over 10-sample period
• USB 3.1 Type-A connectors
• Up to 10Gbps data rate (transparent connection - as far as USB devices are concerned, the meter is just a passive cable)
• 4.1-20V operating range
• Bidirectional - arrow indicates current direction
• Usable as a general purpose power meter - use my USB power/data merger to easily connect to a lab power supply!
• +/- 1% + 20 counts accuracy over operating range
• +/- 0.6 mV/mA precision over operating range
• 17.2 mA self-consumption
• Improved auto-calibration routine over USB-C model