Isotech Better Accuracy in Temperature new ADC free download

File name Better_Accuracy_in_Temperature_new_ADC.pdf

Better Accuracy in Temperature Calibration and Measurement through a New Type of Analog-to-Digital Converter Paul Bramley Metrosol Limited, UK John Pickering Metron Designs Limited, UK This article describes a new reversal-switched DC precision thermometer that achieves performance levels previously attained only with AC resistance bridges. The microK is designed for use in secondary temperature calibration and high accuracy temperature measurement applications (to 0.4mK uncertainty) and is the only precision thermometer that can work with both resistance thermometers and thermocouples at sub mK uncertainties. The use of a touch-screen interface and the elimination of switches, relays and potentiometers from the design make this the first solid-state instrument of its type, thereby providing the highest possible reliability. The core technology is a wholly new type of ADC (analog-to-digital converter) based on the - (sigma-delta) technique but in which the single-bit DAC (digital-to-analog converter) in the feedback loop is replaced by a 5-bit PWM (pulse-width modulation) DAC. The effect of this is to reduce the quantization noise from the - ADC technique by more than two orders of magnitude. The noise performance is then determined by the electronic devices used in the ADC and measurement system, which are lower than existing comparable instruments. Introduction (above ~1000