DROK 0.5" +/- 0-2A DC Current Measurement Panel Ammeter Digital Ampere Meter

I'm a big fan of these guys. I've bought around a dozen over the last year. I work a lot with -20,000V or so and needed something cheap and sacrificial for measuring various loads with that crazy high potential and these are perfect. I used high-capacity rechargeable 9V with a 5V regulator circuit (78L05) soldered to the connector to keep it isolated/floating safely. For powering these, you must have 4.75V - 5.25V. They do use a bit of current if you are using battery, so keep that in mind. It's mainly the LEDs for the 7-seg. I changed the current limit resistors for those 7-seg LEDs to dim it down and cut the current consumption down to 30% and were still bright enough for me.Note that there is a trim pot (variable resistor) for calibrating the offset on the display reading. You do this at 0.000A with no current flowing, obviously and if it's displaying a reading, you adjust it clockwise or counter-clockwise. This is the rectangular blue component with slotted knob shown in their product photo labeled as "Precision Calibration." I calibrated mine vs a Keithley 197A and it holds pretty well within it's 3 1/2 digits ~1% accuracy.I couldn't find a better range for my wanting of milliamps of these since the ones listed here are "0 to 2A," but looking at the back, it was easy to tell that you can configure it with resistor change and jumper change. Adjacent to R11 for the range (200mA, 20mA, 2A) and RA for the current sense resistor. If you change the range 10x's, you simply change the current sense resistor 10x's the other direction. When you change the range, the decimal on the display will move, so don't expect to have 3 after the decimal if you do this.This whole thing is based off of the IC/application circuits of Maxim Integrated ICL 7107 if you want the whole details on all of the circuitry, the IC and everything you could possibly want to know about it.I've been using these for almost a year and haven't had any fail or even need to recalibrate. They're thin, lightweight, accurate, bright, large display, easy to use. My only complaints were the high current consumption, which I resolved, and the range I wanted, which I also resolved with some of my Electronics background.