| 摘要 |
<p>The instrument measuring circuit comprises a terminal (A) connected to a support face of this instrument, on which can be disposed a part to be measured, and a terminal (B) connected to a mobile feeler of the instrument, which is intended to measure a dimension of this part. The terminal (A) is connected up to a source of constant current, itself connected to the positive pole of a battery (21) and consisting of the resistor (R1) and of the transistor (T1), the base of which is biased by the operational amplifier (AO1) so as to maintain the point (c) at the reference potential, which is determined by the diode (Z). The terminal (B) is connected to the negative pole of the battery (21) across a resistor (R2). At the instant when the feeler of the instrument comes into contact with the part to be measured, a potential difference appears across the terminals (d) and (e) of the resistor (R2), which is used, on the one hand, to excite the diode (24) and possibly the buzzer (26) by means of the power (AO2) and variable-gain (AO3) operational amplifiers, and on the other hand, to block the displaying of the measurement furnished by the apparatus (12), by exciting the relay (29) across the logic function (32), by choice, either directly or across a bistable flip-flop (34), which it is a question of resetting to zero by pressing the contact button (35). <IMAGE></p> |
