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    • 摘要: 在利用紫外荧光法对油含量小于10 mg/L的油田回注水进行检测时,光源热功率过大会降低测量结果的精度。为减小光源热功率,提出了光源的脉冲调光方法(占空比小于50%),替代原有的方波调光方法(占空比为50%)。分别建立了基于脉冲调光方法与方波调光方法的噪声分析模型,比较了两种方法的测量结果信噪比(SNR),并推导了测量结果信噪比与光源功率的关系,在信噪比相同的情况下, 可以得出脉冲调光方法的电流幅值与占空比的最优选择方案。结果表明,当测量结果信噪比相同时,脉冲调光方法光源功率不足方波调光方法的21%。最后通过MATLAB软件对两种调光方法的信号解调过程进行仿真,比较了两种方法的测量结果信噪比,仿真所得信噪比关系与理论推导结果一致。

       

      Abstract: When measuring the oil concentration lower than 10 mg/L in reinjection water based on ultraviolet fluorescence method, high thermal power of the light source will reduce the accuracy of measurement results. To reduce the thermal power of light source, pulse modulation dimming method (duty ratio less than 50%) was proposed to replace square-wave modulation dimming method (duty ratio equal to 50%). Two noise analysis models for pulse modulation and square-wave modulation dimming method were built. Signal-to-noise ratio (SNR) of measurement results for two methods were compared. The relationship between SNR and light source power was derived. The optimum choices of current amplitude and duty ratio for pulse modulation dimming method were proposed under the condition of the same signal-to-noise ratio. Results show that the light source power for pulse modulation dimming method is less than 21% of that for square-wave modulation dimming method under the condition of the same signal-to-noise ratio. Finally, signal demodulation models of two dimming methods were simulated by MATLAB software. The simulated relationship of SNR for two methods is consistent with the theoretical analysis results.