| 摘要 |
1,147,655. Measuring peak light intensity photo-electrically. MANUFACTURE BELGE DE LAMPES ET DE MATERIEL ELECTRONIQUE. Oct.3, 1966 [Oct.1 1965], No.44104/66. Heading G1A. [Also in Division H3] In apparatus for measuring the peak value of a light signal e.g. from a thermoluminescent dosimeter, the voltage across a capacitor is made to follow the voltage across a resistor carrying the current from a photo-cell while the current is increasing and to hold the maximum voltage attained. This voltage is then measured. In Fig 1, the resistor 2 and capacitor 3 are effectively connected to the inputs of a differential amplifier 4 so that so long as the voltage across resistor 2 is greater than across capacitor 3, current flows through a diode 5 to charge the capacitor. In a modification, Fig. 2 (not shown) the resistor and capacitor are respectively connected directly between the two inputs of the amplifier and earth and the polarity of the diode is reversed. In order that the capacitor may not be substantially discharged when connected to a voltmeter to determine the voltage attained, an auxiliary capacitor is charged in parallel with the main capacitor and when the apparatus is switched for measuring voltage, the auxiliary capacitor replaces the resistor as input to the differential amplifier, the output of which maintains the charge on the main capacitor, Fig. 5 (not shown). In Fig. 6, the amplifier is a self-oscillating dielectric amplifier (see Division H3). When the capacitor 3 has been charged to its peak value through the diode 5 the switches 16, 17 and 18 are changed over and the short circuit removed from an auxiliary capacitor 3'. The auxiliary capacitor is charged from the output of the amplifier through a diode 19 to a voltage dependent on the voltage on the capacitor 3 and the voltage thus attained is measured by a meter 15. The switching may be effected by transistor switching circuits, Fig. 7 (not shown). |
