Abstract: A differential pressure unit to induce tension and compression in respective strain gages to produce a change in the output of a Wheatstone bridge. The differential pressure or some function thereof is then indicated. Error due to temperature is avoided by maintaining the bridge current constant. The bridge voltage is elevated as a function of temperature to make the bridge current or bridge output independent of temperature.

Abstract: A circuit including a strain gage bridge having a constant current supply at a constant temperature and otherwise variable with temperature. Linearization and accuracy are obtained through a feedback connection. The constant current and temperature compensation features and common mode rejection are also employed to improve accuracy.

Abstract: Analog apparatus for deriving any root of any input variable directly proportional to an input signal. A second signal directly proportional to the logarithm of the variable is divided in accordance with the root selected. The quotient is then compared by an output circuit with a third signal directly proportional to another logarithm which is a logarithm of a second variable which is, in turn, directly proportional to the output signal. The said output circuit compares the quotient and the third signal as two inputs to the output circuit preferably including a relatively high gain differential amplifier to drive a logarithmic amplifier connected to receive the output signal of the differential amplifier, the logarithmic amplifier being connected as a feedback to one input of the output circuit, the differential amplifier driving the logarithmic amplifier output signal to a point such that the said inputs to the output circuit are effectively equal to each other.