Capacitive transducers have proven to be very effective sensors of small displacements, because of inherent stability and noninvasive high resolution. The most versatile ones have been those of a differential type, in which two elements are altered in opposite directions in response to change of the system parameter being monitored. Oftentimes, this differential pair has been incorporated into a bridge circuit, which is a useful means for employing synchronous detection to improve signal to noise ratios. Unlike previous differential capacitive dilatometers which used only two active capacitors, the present sensor is a fullhyphen;bridge type, which is well suited to measuring lowhyphen;level thermal expansions. This analog sensor is capable of 0.1 mgr;m resolution anywhere within a range of several centimeters, with a linearity of 0.1percnt;. Its user friendly output can be put on a strip chart recorder or directed to a computer for sophisticated data analysis.
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