Electronic gage amplifier and display

Abstract

The invention provides an electronic gage amplifier which converts sinusoidal signals representing measurement data from a gage head into a visual display of measurement data. The measurement signals are received by the amplifier at the input of a mixer where they are combined with a coarse adjustment signal. The coarse adjustment signal, which is provided by a multiplying digital-to-analog converter (MDAC) which is controlled by a microcomputer, yields a fine adjustment signal when mixed with the measurement signal. The resulting fine adjustment signal is amplified by a preamplifier, translated into a steady-state voltage by a programmable-gain demodulate-and-hold circuit (D/H) and converted to a digital word by an analog-to-digital converter (ADC). The microcomputer further causes a known reference signal to be processed through the MDAC, mixer, preamplifier, D/H, and ADC. The microcomputer compares the resulting digital word to a known reference value and determines any errors introduced by the aforementioned circuitry. The microcomputer then combines the digital word obtained in response to the fine adjustment signal with a digital word representative of the coarse adjustment signal and a digital word representative of the calculated error introduced by the circuitry in such a manner so as to obtain a correct measurement value which is then displayed.