| 摘要 |
PURPOSE:To attain high accuracy over a wide range, by obtaining a signal nearly independent on a temperature from a difference (beat) signal of an output from plural oscillation circuits having a piezoelectric element which has nearly the same frequency and a temperature primary coefficient and counting output pulses of either one or the sum from the plural oscillation circuits by a time interval determined by the difference signal. CONSTITUTION:An output f1 of an oscillation circuit 12a and an output f2 of an oscillation circuit 12b vary nearly linearly for temperature and each output is expressed by expression [ I ]. Both beat outputs having nearly the same temperature coefficients a1, a2 are shown by expression [II] and are independent on the temperature. When a counter dividing ratio of a counter for gate time 14 is regarded as 1/N (N is an integer), a gate time Tg(sec) at T deg.C is shown by expression [III]. Then, a pulse number DT sent to a counter for counting 16 through an NAND15 is shown by expression [IV] and the pulse number DT in proportion to the temperature T is obtained. Accordingly, the temperature is known by the expression [IV]. |
