| 摘要 |
1,131,136. Measuring bridge circuits. LA TELEMECANIQUE ELECTRIQUE. May 4,1966 May 6, 1965], No.19694/66. Heading G1U. [Also in Division G3] In an arrangement for measuring a number of variables, the variables are converted into electrical parameters such as resistance, and the parameters, e.g. the resistances r 1 . . . .r n , are connected in succession into an arm of a single measuring bridge, the other arms of which are resistors R 1 , R 2 , R 3 , by a switching system including transistors T 1 ...T n which are rendered conducting or non-conducting by pulses from a control unit C. In the embodiment of Fig. 1, the transistors T 1 are normally conducting and the application of a pulse to one of them renders it non-conducting, so that the related resistor is then included in the bridge. In an alternative arrangement the transistors are connected directly into the bridge in parallel and must be switched so as to conduct to include the related resistor in the bridge Fig. 2 (not shown). The output from the bridge is applied via amplifier A and transformer T across a Zener diode Z. If the output amplitude exceeds the unblocking voltage of this, a voltage pulse across the load resistor R c is obtained. The arrangement is used in a temperature control system where it is necessary to scan a number of temperature measuring resistors r 1 .. r n and provide heating when the temperature falls below a preset level. (see Division G3). |
