GB1096992A - Improvements in radiation detectors - Google Patents

Abstract

1,096,992. Flame and like radiation, detection and monitoring. GRAVINER MANUFACTURING CO. Ltd. and WILKINSON SWORD Ltd. Jan. 8, 1965 [Jan. 8, 1964], No. 807/64. Heading G1A. The invention relates to radiation detection systems particularly for use in the monitoring or detection of ultraviolet from flames. According to the invention a detector is provided having electrodes between which an arc discharge can be initiated by incident radiation. This is connected to an A. C. supply and means are provided performing a controlling, warning or indicating function in response to a change in radiation intensity. In a first embodiment transformer TR1 applies 600 V A. C. across detector PC1 and R1 and R2 in series. A capacitor C4 is in parallel with PC1. Above the instantaneous voltage at which the detector breaks down in the presence of radiation an oscillating voltage appears across PC1 due to the repeated charge and discharge of C4. The voltage developed across R2 is applied to a discriminator comprising a multi-vibrator T1, T2 and negative half cycles cause T2 to conduct and energize relay RL resulting in illumination of warning lamp L1. Capacitor C2 holds the relay during the positive half cycles. It is stated that a short circuit in the detector resulting in the application of the transformer secondary waveform to R1 and R2 results in a signal of lower peak amplitude being applied to the discriminator circuit, such lower signal not being capable of operating the relay. Other embodiments rely on the breakdown of the detector to apply an A. C. voltage to a bridge rectifier energizing a lamp control relay. An integrating circuit introducing a time delay may be incorporated to reduce the effect of spurious signals. In the circuit of Fig. 3 (not shown) a bridge rectifier is in series with the detector and its smoothed D. C. output applied to a relay controlling the warning circuit. In a more complex circuit the bridge rectifier output controls this warning device via a silicon controlled rectifier.