Apparatus for monitoring the liquid level in a tank
AssigneeSiemens Aktiengesellschaft
InventorHelmut Glaser
Life of this patent
Estimating the term…
Abstract
In apparatus for monitoring the liquid level in a tank which includes a resistance bridge supplied with d-c current having two bridge arms arranged inside the tank, one of which is electrically heated, with the output of the resistance bridge followed by a signal stage with a binary indication and by a current regulator for the heating current, and a testing arrangement for simulating a given filling level, the resistance bridge is supplied from a constant current source whose current is switched from one current value to another upon the operation of the testing device in order to preclude operating disturbances during the testing.
Claims9
In apparatus for monitoring the liquid level in a tank, which includes a resistance bridge supplied with DC current having two bridge arms arranged inside the tank with one of these bridge arms electrically heated, an output signal stage with an output indication in the form of a binary level, and a current regulator for the heating current of the heated bridge arm having the output of the resistance bridge as a control input, said apparatus including means for testing the operation of the monitoring device by simulating a given filling level, an improved means for testing comprising:
- a. a constant current source for supplying at least two DC currents of different magnitude;
- b. means for initiating testing;
- c. a switching device, having its control input coupled to said means for initiating testing, for selectively coupling one of the two currents of different magnitude to the resistance bridge;
- d. an analog value storage device interposed between the current regulator and the bridge;
- and
- e. means responsive to said means for initiating testing for interrupting the connection between the output of the resistance bridge and the current regulator when the testing device is operated.
Dependencies are inferred from the claim text.