Measurement and Calibration

The following information may help in selecting the appropriate measuring device for your needs.

Accuracy
The precision of the instrument which can be reported in three ways.
1. By quoting the guaranteed tolerance as a percentage of the reading or indicated value, (eg. “0.5% of Reading”).
2. By quoting the guaranteed tolerance as a percentage of the full scale value of the instrument, (eg. 0.1% FS or 0.1% FSD).
3. By quoting a ‘class’ of device in accordance with BS7882:2008 “Method for calibration and
classification of torque measuring devices”. (See page 90).

Modes of Operation
First Peak of Torque - when a “click type” torque wrench signals that the set torque
has been achieved, the applied torque will momentarily drop before climbing again. Generally
the fastener stops rotating at point 1, and from a standstill, the breakaway torque to achieve
further rotation of the fastener will be higher than point 3b. Only if the operator is very
insensitive to the break point will the final tightening effort be incorrect.
“First Peak of Torque” mode will detect the break point of the torque wrench, not the
highest torque applied.

Peak Torque - this mode of operation will record the highest torque applied. In the
case of a “click type” torque wrench this may be higher than the actual break point if the
wrench continues to be loaded beyond the break.
Consequently, Peak Torque is more useful for calibrating devices without a break signal such as dial or electronic wrenches.

Track - this mode has no memory at all.When the load is removed the display will return to zero.
Track is used for calibrating the device itself or for monitoring a fluctuating torque.