Measuring Cell-To-Cell Rather Than Cell-To-Bar; Adjusting Sensitivity - Elcometer 331 Series Operating Instructions Manual

R
A
DJUSTING SENSITIVITY
Figure 14. Typical instrument configuration for half-cell measurements

8.3 Measuring cell-to-cell rather than cell-to-bar

In some instances it will not be possible to make a direct connection to a reinforcing bar. In this
situation it is common practice to use two half-cell probes connected to the inputs of the
Covermeter. One probe is fixed in position on the concrete surface and the other probe is moved
over the surface. In this way the surface can be 'mapped'.
Using this method, the absolute value of the reinforcing bar to concrete half-cell will not be
measurable, however changes from one point on the surface to the next can be measured and
interpreted.

9 ADJUSTING SENSITIVITY

The sensitivity setting is indicated by the variable wedge-shaped symbol on
the display. To increase the sensitivity, press [ ]. To decrease the
sensitivity, press [ ].
Typically, set the sensitivity to produce a slow 'clicking' sound in the absence
of metal. With the sensitivity set at this level you will be able to differentiate
quickly between bars of the same size located at different depths.
If the sensitivity is optimised, the pitch of the sound will consistently give a good guide to the extent
of cover; shallower-than-average bars will produce a clearly noticeable, more intense sound, which
will draw your attention to such bars. However, if the sensitivity has been adjusted to an arbitrary
level, the necessary degree of consistency may not be achieved.
22