| 摘要 |
1,203,049. Electro-chemical analysis; voltage measurement. ALBERT MEASUREMENTS Ltd. Nov.27, 1968 [Dec.6, 1967], No.55426/67. Headings G1N and G1U. A high input impedance, differential, transistor voltmeter is used with e.g. glass electrodes for pH measurement. The DIFFERENTIAL TRANSISTOR VOLTMETER comprises an F.E.T., Q1, with a high-gain, emitter follower Q2; microammeter M1, and a mirrorimage-circuit including F. E. T., Q4 and transistor Q 4 . OVER-VOLTAGE & TRANSIENT PROTECTION is provided by a filter circuit R9, C1, together with neon N1. Also the input may be shortcircuited by switch S1 to protect against surge voltages when changing the electrodes from one sample to another. pH CALIBRATION. With the electrodes in a standard solution of known pH, R4 is adjusted to obtain a required deflection on M<SP>1</SP> corresponding to the pH. Sample temperature compensation may be introduced manually by R7 or R7 may be replaced by a platinum resistance thermometer. |
