It's small! I know the size is stated clearly, but I was still surprised. You can hook this meter up in 2 ways: 1) 2-wire: Black to ground, red & white to pos. power source. The meter is powered by the same source it is measuring. Pros: Simple setup, only 2 wires needed. Good for placing in a vehicle. Cons: Limits the measuring range to approx. 3-30v. In a dark room, I could start to see the display at about 2.4v, and at about 3v I could see it in a lit room. It seemed to reach full brightness at about 4v. 2) 3-wire: Black to ground, red to 3-30v power source, white to pos. power source to be metered. Pros: Allows full range of metering, 0-100v (according to specs). Good for benchtop needs, and for measuring outside the 3-30v range. Cons: Requires a separate power supply for the meter. Power supply and source to be metered both need to share the same ground. The pros and cons cited above must be weighted to your requirements; they may not be pros or cons at all for you! No instructions come with the meter but the product description on amazon is sufficient for hookup. The green color is bright and looks nice. I just got it so I have no feel for the longevity. For the price it seems like a nice product if the limited accuracy isn't a problem. For mounting in a vehicle, it is probably OK, although there are many nicer looking options available for that. For the benchtop, it is OK for quickly ball-parking or checking a voltage. Some Details: The leads are 6" long and tinned at the tip. My power supply has a range of 1.25-18v, so I did not test it outside of this range. It has a (very) small calibration pot on the back, I had to hunt for a screwdriver that could turn it. I finally found one with a 1.5mm flat tip that was just large enough without being too large. With my power supply reading 17.82 on my multimeter, the volt meter read 18.1 and I was able to calibrate it back to 17.8. Under 10v, you only get two digits. A third digit would have earned it another star. At any voltage of course, the low digit is suspect. When you change the voltage being metered, the display is a little slow to catch up due to the 2Hz measurement rate. Not crisp, but ok. Using the 3-wire hookup, I measured 0mA current draw at 1.25V, and 0.04mA at 17.8v, across the metered power, not the supply power. Using the 2-wire hookup, I measured 2.5mA current draw at 2.5V, 11.4mA at 12V, and 12.5mA at 17.8v.
