充气型紫外光敏管降噪研究

充气型紫外光敏管噪声过大是紫外火警探测系统最难克服的问题。本文从器件制造和使用的角度分析了影响紫外光敏管噪声的重要因素,探讨了降噪措施:制造工艺方面,采用高纯度金属镍基阴极材料和保持阴极表面质量良好,充分老化器件,选择高纯度氢气为主充气体并控制充入氦气比例不高于15%;使用方面,降低器件工作电流和工作电压可进一步减小器件噪声。最后采用锁相放大进行噪声测试,在120ms内,测得紫外光敏管噪声电压均值为0.0065V,测试不确定度为7.4%;在无外界紫外照射下,经脉冲计数,测得单位时间内紫外光敏管累积输出噪声脉冲为10cpm,显著降低器件噪声。

Study on noise reduction of gas-filled ultraviolet phototube

Overlarge noise of the gas-filled ultraviolet phototube is the most difficult problem to overcome for the ultraviolet fire detecting system. In this paper, the most principal influence factor of gas-filled ultraviolet phototube had been analyzed and the noise reduction technique been investigated through discussing device preparing process and application. During the device preparing process, the ground noise can be reduced by means of selecting high-purity Nickel as the cathode material and keeping the cathode surface quality perfect, by ample ageing processing, selecting high-purity hydrogen gas as the main filling-gas and filling the tube with helium gas at a ratio of no more than 15%. The noise can be further reduced through decreasing the operating current and voltage of the ultraviolet phototube during using it. By adopting phase-locked amplifier noise measuring technique, the average noise voltage of the tube was measured to be 0.0065V and the measuring uncertainty degree to be 7.4% in 120ms. On condition that no outside ultraviolet radiated, the accumulated noise pulse output of the tube in one unit time was measured to be 10cpm by pulse counter. The result demonstrated that the device noise had been notably reduced.