The XTR108 is a “smart” programmable, two-wire transmitter designed for temperature and bridge sensors. Zero, span, and linearization errors in the analog signal path can be calibrated via a standard digital serial interface, eliminating manual trimming. Non-volatile external EEPROM stores calibration settings.
The all-analog signal path contains an input multiplexer, autozeroed programmable-gain instrumentation amplifier, dual programmable current sources, linearization circuit, voltage reference, sub-regulator, internal oscillator, control logic, and an output current amplifier. Programmable level shifting compensates for sensor DC offsets. Selectable up- and down-scale output indicates out-of-range and burnout per NAMUR NE43. Automatic reset is initiated when supply is lost.
Current sources, steered through the multiplexer, can be used to directly excite RTD temperature sensors, pressure bridges, or other transducers. An uncommitted operational amplifier can be used to convert current into a voltage.