Weighing device with electromagnetic force compensation - has permanent magnet with compensation coil and resistor network with temperature compensation

摘要

The load to be weighed is applied to the compensation coil. The device comprises further an indicator for the compensation coil zero position. A control amplifier for a signal delivered by the indicator, whose output current is applied to the compensation coil, tends to hold the coil in its zero position; this current is a measure for the load. The permanent magnet has an additional correction coil which corrects the magnet field strength changes due to the compensation current. Its temperature variations are compensated by a resistor network with a temperature sensitive PTC resistor. The correction coil itself serves as the temperature compensation resistor and its material is a metal having good electrical conductivity.