For certain highly loaded mechanical drive elements,
performance. Monitoring the joint with an IRt/c pro-
such as the main rotor drive for a helicopter, it is
vides a fast and direct indication of joint temperature,
imperative that impending failure be detected
thus the decreased efficiency due to wear or failure.
before a catastrophe occurs. A central element of
An even more sensitive method of monitoring the
the drive, such as a universal joint or coupling, will
joint is to employ two IRt/cs wired differentially.
telegraph its impending failure well in advance by
Connect the two minus leads together and measure
displaying an increase in temperature. For example,
across the plus leads, as illustrated. This allows you
consider a drive transmitting 1,000 hp (750 kW) of
to measure the difference in temperature between
shaft power through a universal joint, losing only
the joint and adjoining shaft. The difference is a direct
0.1% in drive efficiency. The joint will increase in
Quick installation guide
measure of the heat created in the joint and will not
temperature as much as several hundred degrees
be influenced by ambient temperature effects,
until it is able to dissipate an additional 750 W of
energy as heat. This increase in temperature is
pre-calibrted models
since the differential pair arrangement cancels those
effects. Accordingly, a very high precision can be
a direct and reliable indication of the increased
achieved. An IRt/c with built-in air purge is recom-
inefficiency caused by a degradation in parts
mended if the environment is oily or dusty.