Thermistor sensor vehicle fuel gauge - has thermally coupled positive and negative temp. coefft. thermo-resistors on supply terminals with output taken at mid-point

摘要

A PTC thermistor (11) is connected in series with and thermally coupled (14) to a negative temp. coefft. thermistor (15) between earth and the positive terminal of a power source (12). An electrical quantity is picked-up at the output terminal (13) which is at the mid-point (M) between the two thermoresistances. Thermal coupling between the two thermistors is achieved either by joining one to the other by adhesive or solder through an opening in a PCB, or by a metallic plate with the thermoresistances soldered opposite each other one on either side of the plate. The printed circuit or metallic plate then forms the mid-point between the thermoresistances. The level gauge has several such pick-ups connected in parallel to the terminals of a power source in order to supply a common operating circuit, which has one comparator per pick-up. One input of each comparator is connected to the output of its corresponding pick-up while the other inputs are connected in parallel to the same reference source. The outputs of the comparators are connected in parallel via a galvanometer to the pick-ups power source.