| 摘要 |
PURPOSE:To obtain a water depth detecting circuit for an electronic wrist watch wherein an LCR oscillating method having excellent temperature characteristics is used in a simple constitution, and inductance which is varied with the water depth is detected by an LCR oscillator using a resistor having the temperature characteristics. CONSTITUTION:The gate voltages of an invertor 4 and a driver 5 are always the same, and internal resistances do not impart large effects to each other. When the temperature of the invertor 4 and the driver 5 increases, the oscillating frequency is increased. However, the resistance value of temperature compensating resistor 3 such as a thermistor having negative temperature characteristics is decreased and the resistance value of a detecting coil 1 is increased. Therefore the oscillating frequency is increased. As a result, the oscillating frequency change is offset as a whole. If the value of the temperature compensating resistor is made large to some extent, the effect of dispersion in resistance values of the invertor 4, the driver 5 and the detecting coil 1 can be alleviated and current consumption can be decreased. |
