抄録
The conventional moving coil meters used for temperature measurements in conjunction with a thermocouple or resistance bulb often suffer from troubles due to their small drive torque and delicate mechanical construction.
The purpose of this paper is to discuss a temperature indicator which is newly developed with the intension of solving such common problems.
The indicator unit is essentially composed of a pair of fixed cross coils and a movable permanent magnet with a pointer and used together with an IC amplifier.
A signal voltage from a suitable temperature sensor is, after amplification, applied to the junction point of the coils, being series-connected and powered with a stable DC source. The amplifier output controls the respective currents through the coils and hence induced magnetic fields. The magnet, located in the center of both coils takes the direction of the resultant field and indicates the input signal.
In order to attain reasonable damping characteristics, a pair of damping coils are placed close to the magnet. The induced voltage, nearly proportional to the angular velocity of the magnet, is applied to the amplifier for negative feedback.
The indication characteristics are theoretically analyzed and compared with the experimental data. The indication difference has been reduced to 0.2% of full scale by means of electronic adjustments and magnetic compensation.
It is possible to obtain a large indicator torque such as 5 to 6mg-cm/deg, about 10 to 30 times larger than by conventional moving coil meters.
