The
SSP1492 (
Product
Brief) will interface directly with the
Piezoresistive Bridge Outputs provided by
RTD, or Temperature sensors. Up to 16 temperature sensors may be input into just one SSP1492. The SSP1492 utilizes a unique frequency mode data acquisition technique which converts sensor output into a frequency-based signal by placing the sensor element into a resistance-capacitance (RC) oscillator as shown in Figure 1. The oscillator circuit consists of a comparator with a positive feedback loop to create an oscillator which converts the time-varying sensor signal into a square wave with a varying time period. This signal can be counted and digitized into a value that is proportional to the oscillator frequency, and in turn, proportional to the sensor’s measurement. In the RC oscillator configuration, the sensor is introduced as a variable resistor (R) with an external fixed capacitor (C) in the circuit. A period counter unit (see Figure 2) demodulates and digitizes the output signal from the sensor oscillator section, and can measure two parameters of time-varying signals: cycle period and pulse width. The sensor data converter has scalable dynamic range, accuracy and speed and can easily be scaled from less than 8 to over 24 bits of conversion resolution.
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