CA330 RTD Calibrator: High-speed Response and High-resolution Resistance Simulator

摘要

Yokogawa Meters & Instruments Corporation has developed the CA330 handheld process calibrator, a resistance temperature detector (RTD) model. We thoroughly reviewed the design of the ohms source function which has been a long-standing problem. In particular, high resolution and high-speed response were achieved by using a new technology of the improved feedback type PWM method, thus successfully raising the carrier frequency without degrading the PWM resolution. As a result, we changed the demodulation processing of the multiplying digital-to-analog converter (DAC) with pulse width modulation (PWM) from the conventional section integration method to a simple low-pass filter method, increasing the processing speed. As a result, the CA330 has achieved a response of less than 5 msec with the setting resolution of 10 mW. This paper introduces the redesigned ohms source function and improved feedback-type PWM.