Abstract: This invention relates to an analog to digital convertor in which zero drift and span drift are eliminated. The first differential amplifier has inputs of an analog voltage which can be switched between its positive input terminals in polarity and a reference voltage which can be switched between its negative input terminals. The output of the summing amplifier is integrated in a positive differential integrator, preferably, and fed through a crossover detector to detect crossover of the signals from the two sides of the integrator. Integration is carried out while adding the reference voltage and the analog voltage over a first fixed time period. The reference voltage is then reversed over a second time period to perform a first conversion. The start and stop signals of these time periods are used to start and stop a pulse counter.

Abstract: Column-type load cells having recessed portions on opposite sides to receive strain gauges mounted on the web in the recesses for more linear response are improved by reduced cross sections off each end of the recesses, and/or by flexures off each end, with adjustment of the diameter of the reduced diameter portions and the distances of the flexures from the recesses to adjust the linearization effect of the recesses. Diaphragms arranged either at one end or both ends are used to support a tube cover. Utilizing two diaphragms, one at each end of a tube cover has been found to improve linearization even without reduced cross sections and/or flexures.

Abstract: Two operational amplifiers are hooked in a different mode by unique circuitry so that the common mode gain is unity and the open loop gain is the same as the open loop gain of the individual amplifiers. Essentially, a negative feedback network feeds the common mode output signal back to the negative input terminals which cancels the common mode output signal. Practical applications are achieved by adding appropriate integrating capacitors between the output and negative inputs of the amplifiers with appropriate series resistances in the input leads.

Abstract: The scale includes a horizontal load plate and base plate supported in spaced parallel relationship by first and second generally rectangular members lying in vertical spaced planes extending between the load plate and base plate. Opposite end portions of each rectangular member are symmetrical about a vertical axis passing midway therethrough, these opposite end portions defining corner flexure supports connected between the vertically opposed corner portions of the load plate and base plate.A load element in each of the corner flexure supporting means will flex under load and has strain gauges attached thereto to provide electrical read-out signals constituting a function of a force applied to the load plate. The design of each of the corner flexure supporting means is such that the strain gauges are isolated from extraneous strains resulting from off-center application of a force on the load plate.