Checkline MX-5 - Manual (Page 11)

MX-5 Ultrasonic Thickness Gauge
7
The Display
The numeric portion of the display consists of 4 complete digits
preceded by a leading "1", and is used to display numeric values, as well
as occasional simple words, to indicate the status of various settings.
When the MX-5 is displaying thickness measurements, the display will hold
the last value measured, until a new measurement is made. Additionally,
when the battery voltage is low, the entire display will begin to flash.
When this occurs, the batteries should be replaced.
These eight vertical bars form the Stability Indicator. When the MX-5 is
idle, only the left-most bar and the underline will be on. While the gauge is
taking a measurement, six or seven of the bars should be on. If fewer than
five bars are on, the MX-5 is having difficulty achieving a stable
measurement, and the thickness value displayed will most likely be
erroneous.