| 摘要 |
PURPOSE: To set off the effect of reactance having positive temperature coefficient against the effect of resistance and improve the measurement precision by installing a primary and a secondary coils, a sinusoidal oscillator to send a.c. signals to the primary coil, a first and a second operational amplifiers, and a means which amplifies a.c. signals induced by the secondary coil and displays the signals. CONSTITUTION: A sinusoidal oscillator 11 generates a.c. voltage e1 , the voltage is applied to an operational amplifier 12 through a resistor RS1 , and at the same time the voltage is applied to one end of a primary coil L1 having resistance R1 , and the other end of the coil L1 is connected with the output of the operational amplifier 12. A secondary coil L2 having resistance R2 is connected with a resistor RS2 , the a.c. voltage e2 which the resistor RS2 shows is applied to one input of an operational amplifier 13, and the output of the operational amplifier 13 is connected with an input of another amplifier and at the same time the output is sent to an amplifier 14. The signal is converted by an AC/DC converter 15, converted by an A/D converter 16, and computed by a computer 17, and shown as film thickness by a display 18. |
