Review on Precision Measuring Made Easy With GemRed Digital Tool Set For Table Saw - GR905 Angle Gauge GRSET905 by Mark Glass

Always powers up in absolute mode (digital level). Pushing the ZERO button makes it a relative angle gauge. I have tested this with the reversal test on a surface plate, on some machine tool beds with 123 blocks, and also on a homemade angle table through a range of 0 to 2.5 degrees. The reading from the base is generally self-consistent and repeatable to 0.1 degrees, but turning it on the left and right edges reads 89.9 one way and 89.8 the other, instead of 90.0 and turning the base from 0.0 through a precise 90 angle with a 123 block, it reads 89.9 degrees. When you turn beyond 90.0 degrees, the digits turn upside down on display, then it counts back down again so it reads 0.0 (+/- 0.1) when exactly upside down. When leveling near zero, sometimes it bounces repeatedly between +0.1 and -0.1 (missing 0.0) even with slow and minute angle changes, but then a minute later 0.0 appears. It may need to settle for a minute or more upright on the base (not flat on its back) before measuring. Only one edge (the base) is magnetized. It has a solid grip on thick steel surfaces. It is not as strong, but it will just hold up its weight on a thin piece of vertical sheetmetal like the edge of my range hood, and even when that surface does not cover the full width of the base (see photo). Single AAA battery included. Backlight turns off after 30 seconds of no movement, but digits still show on LCD display. Just moving it turns the backlight on again. It turns off completely after being still 5 minutes.