Abstract: The output of a condition sensing bridge is linearized by providing a feedback from the output to the bridge supply which feedback is in the linear form of V.sub.B =KV.sub.O +V.sub.X where V.sub.B is the bridge supply voltage, K is a proportionality constant, V.sub.O is the bridge output and V.sub.X is the feedback offset voltage.

Abstract: A catalytic combustion type CO gas sensor which is composed of an electrical circuit by serially arranging two coils composing an active section and a compensating section, and by providing serial bridge resistances, r.sub.1 and r.sub.2, opposing to the said coils, respectively, and via a gas sensitometer, and which determines the CO concentration based on the difference in value of resistance of both coils of the active section and the compensating section on catalytic combustion of CO, characterized by:(A) that the values of the resistance of coils of the active section and the compensating section and bridge resistances, r.sub.1 and r.sub.2, at a definite temperature are made substantially the same, and thus the temperature coefficients of the coil of the active section and the bridge resistance r.sub.1, and of the coil of the compensating section and the bridge resistance r.sub.2 are made approximately the same.(B) that the value of resistance of the coil of the active section at 150.degree.-200.degree.

Abstract: In a switchable impedance tester for measuring very small impedances, the effect of switch impedances is eliminated by connecting the test load between two switching transistors in their emitter-collector circuit, and driving them with operational amplifiers arranged to urge their inputs into equality. A test voltage source is connected across first inputs of the amplifiers, and the other inputs are connected between the respective transistors and the load. This produces an operational condition in which the voltage across the load is independent of the parameters of the switching transistors, i.e. the switching transistors appear to have zero impedance.

Abstract: For measuring the inductance of a workpiece, a device which includes an inductance meter, respective D.C. and A.C. power sources as well as a guard line circuit. In order to simulate conditions of actual use of the workpiece, the D.C. power source is connected to provide a direct current bias through the workpiece. A measuring current produced by the A.C. power source and applied to the workpiece is detected via the inductance meter. The guard line circuit is coupled so as to prevent any portions of the A.C. measuring signal from undesirably flowing through the D.C. power source.

Abstract: The invention concerns apparatus for the non-destructive measurement of the ohmic resistance of thin layers. The apparatus is based on a capacitative measurement process wherein the plates of a capacitor are formed by an electrode (3) with the thin layer (6) to be measured, the dielectric of the capacitor being constituted by a carrier foil (5) on which the thin layer (6) is carried, for instance by means of a vacuum-depositing process. The electrode (3) is supplied via an oscillator with high-frequency voltage (U.sub.HF) so that a displacement current flows from the electrode (3) over the carrier foil (5) to the thin layer (6) and from there back again. This displacement current is composed of an ohmic part and a capacitive part. In order to maintain the capacitative part constant even for fluctuating capacitances, caused e.g. by changes in the thickness of the carrier foil (5), an additional capacitor is connected in a regulated manner to the capacitor that is present.