| 摘要 |
1,191,277. Printed circuit resistors and capacitors. PLESSEY CO. Ltd. 1 Sept., 1967 [19 Sept., 1966], No. 41745/66. Headings H1M, H1R and H1S. In a thin film printed circuit the resistance value of resistors, formed by vapour deposition on a glass substrate, are arranged to be initially lower than the required value and then the values are adjusted within limits of tolerance by scribing an incision. For example, in Fig. 1, a resistance value of 1000# is required. A resistor 11 is therefore connected to probes 32, 33 (Fig. 3) of a measuring bridge 31 which is adjusted so that the bridge will be balanced when the resistor 14 is 990# to an accuracy of Œ0À1%. The unbalance output energizes a servomotor 35 (Fig. 3) which moves a scribe 38 to make an incision 14 in the resistor 11 which increases the resistance value until the bridge is substantially nulled. A second resistor 15 having a nominal value of 8# is provided in series with R 11. The resistance of R11 is then measured to an accuracy of 0À01% and the required value of R15, to make the series combination 1000#, is calculated. R15 is then connected in the bridge circuit which is set to the calculated required value and an incision 17 is made as described above, an overall accuracy of Œ0À011% thus being obtained. Alternatively the resistors may be connected in parallel (Fig. 2, not shown), or the adjusting device may be applied to capacitors. |
