At the end of this lesson, the students would be able to
(i) show the general principle of measurement
(ii) classify and apply different transducers for converting cutting forces
into suitable signals
(iii) state the design requirements of tool-force dynamometers
(iv) develop and use strain gauge type dynamometer for
(i) General principle of measurement.
The existence of some physical variables like force, temperature etc and its
magnitude or strength cannot be detected or quantified directly but can be so
through their effect(s) only. For example, a force which can neither be seen
nor be gripped but can be detected and also quantified respectively by its
effect(s) and the amount of those effects (on some material) like elastic
deflection, deformation, pressure, strain etc. These effects, called signals,
often need proper conditioning for easy, accurate and reliable detection and
measurement. The basic principle and general method of measurement is
schematically shown in Fig. 10.1.
The measurement process is comprised of three stages:
Stage – 1 : The target physical variable (say force) is converted proportionally
into another suitable variable (say voltage) called signal, by using
appropriate sensor or transducer.
Stage – 2 : The feeble and noisy signal is amplified, filtered,
rectified (if necessary) and stabilized for convenience
and accuracy of measurement.
Stage – 3 : where the conditioned signal (say voltage) is quantitatively
determined and recorded by using some read out unit like
galvanometer, oscilloscope, recorder or computer.