Johnson Level & Tool Mfg. 40-6001 - Manual (Page 29)

©2013 Johnson Level & Tool - Rev. 3 29
Tips from the Pro’s
Take more than one measurement in critical situations where accuracy
needs to be greater than an estimation measurement. Take 3-4
measurements from the same position to compare consistency of each
reading. Prior to important measurements verify that the instrument is in
proper working order and take sample measurements of a known
distance to verify accuracy.
To accurately measure from the rear of the instrument, use a scrap piece
of drywall or other flat material. Extend the material off the corner and
butt the LDM up to the material. Then take measurement.
Place a white sheet of paper over the targeted measuring surface if error
message Err02 occurs to improve the return signal.