Which has a precision ground bottom surface, normally with V shape channel at the bottom for standing on round objects.
With a precision made water level scale. This level can show 4 seconds of inclination change.
You don't need to use a flat reference surface to zero it. Just simply place it on a clean, rigid surface.Shim the surface to roughly flat level, then the water bubble will move to somewhere in between of the scale.In this case, I've placed my level on x-rail.Waiting for a while, let the water bubble steady down, record the reading. Then turn the level in 180 degree opposite orientation and sit down on the same surface.
I've used the edge of the saddle for position reference, so I can put the level back to the same position.Again, waiting for a while, let the water bubble steady down, record the reading. If the readings are the same, the level was zeroed.
If you have reading different, divide it into two, that's the amount of inclination you need to adjust for zeroing this level.
Adjust the zeroing screw or set screw on the level, try to achieve half of the reading different and let the water bubble move from larger reading side to smaller reading side.
Finally, the level will be zeroed.
