The AD7713 is a complete analog front end for low frequency measurement applications. The device accepts low level signals directly from a transducer or high level signals （4 : VREF） and outputs a serial digital word. It employs - conversion technique to realize up to 24 bits of no missing codes performance. The input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by an on-chip digital filter. The first notch of this digital filter can be programmed via the on-chip control register， allowing adjustment of the filter cutoff and settling time. The part features two differential analog inputs and one singleended high level analog input as well as a differential reference input. It can be operated from a single supply （AVDD and DVDD at 5 V）。 The part provides two current sources that can be used to provide excitation in 3-wire and 4-wire RTD configurations. The AD7713 thus performs all signal conditioning and conversion for a single-， dual- or three-channel system. The AD7713 is ideal for use in smart， microcontroller-based systems. Gain settings， signal polarity， and RTD current control can be configured in software using the bidirectional serial port. The AD7713 contains self-calibration， system calibration， and background calibration options and also allows the user to read and to write the on-chip calibration registers.