Electromagnetic load-compensation weighing apparatus including temperature compensation means
AssigneeMettler Instrumente AG
InventorArthur Reichmuth
Life of this patent
Estimating the term…
Abstract
Weighing apparatus of the electromagnetic load compensation type is provided with a movable coil arranged in the air gap of a permanent magnet system, and which includes a load-compensation winding through which flows a load-dependent compensation current. As a temperature sensor for measuring the coil temperature, use is made of the coil, specifically, either the load winding itself or an additional winding that is in thermal contact with it. A resistance measuring device determines its temperature-dependent resistance from the voltage and the current on or in the winding. Accurate and real-time measurement of the coil temperature as a measure for controlling the compensation of its influence on the measurement reading is possible in this way.
Claims9
weighing apparatus of the electromagnetic load compensation type, comprising:
- (a) stationary permanent magnet means (4);
- (b) a load-receiving member (1) mounted for movement relative to said permanent magnet means,
- (c) at least one load compensation winding (2) connected with said load receiving member;
- (d) means (6) for supplying load compensation current (i.sub.L) to said load compensation winding for maintaining said load-receiving member at its initial no-load position, whereby the magnitude of said load compensation current is a function of the load applied to said load-receiving member;
- and
- (e) temperature-responsive means for generating a parameter for compensating for the influence of temperature changes in said load compensation winding on the measurement result, including:
- (1) sensor winding means on said movable load-receiving member;
- and
- (2) means (10;
- 11, 14;
- 15-17;
- 9) for measuring the temperature-dependent resistance (R.sub.L ;
- R.sub.Z) of said sensor winding means as a function of its voltage (u;
- U) and current (i.sub.L ;
- I).
Dependencies are inferred from the claim text.