| 摘要 |
1,228,708. Analogue/digital converters. BAXTER LABORATORIES Inc. 21 May, 1969 [19 June, 1968], No. 25911/69. Heading G4H. An analogue input signal for example from a spectrophotometer is stored on a capacitor 46 (Fig. 1) and compared at 38 with an exponentially decreasing signal from the capacitor C, at equality a relay K2 being operated to change over its contact AB and so terminate the supply of clock pulses to a counter/printer unit 10. In the embodiment described the capacitor C is charged from a reference source until a start switch 30 is operated to energize relay K1 to change over its contacts A, B, C, D, to allow the capacitor to discharge and to start the count of pulses derived from a mains transformer 24. Calibration.-The gain of an amplifier 40 connected to the spectrophotometer output is first adjusted, with an input sample of pure water, by varying the potentiometer 44 until relay K2 becomes energized, the gain being slightly decreased from that position. The potentiometer may include both coarse and fine adjustment. A known sample is then tested and a relay R in the capacitor discharge circuit adjusted until the counter 10 gives the required digital value. |
