The MQ 0117 combined bimetallic instrument is intended especially for thermal monitoring of transformers, cables, etc. due to its slow reaction to current changes. It indicates mean r.m.s. current value during the measuring period of the instrument. The instrument does not react to short current pulses essentially. Maximum mean value in a response time period is indicated by the red slave pointer. The latter can be reset or set to zero by means of a knob which can be sealed. Besides the bimetal system the instrument also includes a moving-iron system which measures instantaneous r.m.s. values.
Combined bimetal maximum current meters are provided with a built-in bimetal system and a system with a moving iron. Special instrument design enables quick replacement of the scale both in case of a new or an already used instrument. This is especially suitable for instruments which are connected to current transformers.
The exchangeable scale has a number of advantages:
MQ 0117 is the same as the one on the photo, except its front frame is 144x144 mm.