With the sensor head located in position adjustment belt tension adjustment can now be undertaken. This can either be performed manually or fully automatically in a closed loop setting technique.
Manual adjustment requires the operator to adjust the belt tension into the required frequency range either by looking at the frequncy readout or by following 'SLACK-O.K.-TIGHT' indicator lamps on the equipment.
Closed loop operation removes any decision making from the operator. For applications where belt tension is set by a screw jack adjuster, a power tool is placed onto the screw adjuster which is then wound down under the command from the tension measurements. This is a very high speed operation and takes as little as 4 seconds. For applications where the belt tension is set by swinging one of the driven components (such as the alternator) outwards, a pneumatic cylinder is used, with air admission and release, again under the command from the tension measurements.