R
13
divisions every half-centimetre (5 mm) up to 6 cm on the LOW range and up to 8 cm on the HIGH range,
and every centimetre thereafter.
The black 0-100 scale at the bottom can be used to compare signal strengths, or for preparing calibration
curves for bar sizes outside the 12 mm to 20 mm range (see “Bar size” below).
4.2 PRECAUTIONS WHEN MEASURING COVER
BATTERY VOLTAGE
The Elcometer Protovale 120 Rebar Locator is calibrated for a battery voltage corresponding to a BATT test
indication in the middle of the green diamond. This voltage corresponds to a battery halfway through its
usable life, and so yields adequate accuracy during most of the battery life. A brand new set of batteries
which, on BATT test, indicate to the right of the green diamond will, on cover measurement, indicate to the
right of the true cover, and therefore read low by up to about 5 mm. Similarly a nearly-exhausted battery
which reads to the left of the diamond on BATT test, will read to the left of the true cover, ie. high by up to
5 mm.
BAR SIZE
The Elcometer Protovale 120 Rebar Locator is calibrated for a bar of 16 mm diameter, and this calibration
also adequately suits the adjacent sizes of 12 mm and 20 mm. For bar sizes outside this range, the
Elcometer Protovale 120 Rebar Locator will overestimate the depth of smaller bars, and underestimate the
depth of larger bars. For example, at nominal battery voltage, a 10 mm bar will read high by 3 mm to 4 mm
on the LOW range and by 5 mm to 7 mm on the HIGH range; a 25 mm bar will read low by about 4 mm at
shallow covers or about 10% when deeper. If measurement of cover over bars outside the 12 mm to 20 mm
diameter range is a regular requirement, a calibration chart could be drawn up, using the linear 0 to 100%
DISCONTINUED