dc.description.abstract | This research proposed a design of the innovative airglow instrument, which can extend the measure range of the light intensity, and also have the influence of strong light protection. The innovative instrument uses the photomultiplier tube to detect the photon count, then by the photon count to feedback and control the high voltage of the photomultiplier tube to reimburse for the change in light intensity and remain the photon count fixed. While the photon count is controlled to maintain fixed, the light intensity is inversely proportional to the high voltage, and then the light intensity can be reckoned from the high voltage. The photon count is the function from the light intensity and the high voltage, representing the characteristic surface of the photomultiplier tube. The experimental data can be used system identification algorithm to establish its mathematical model of quadratic polynomial equation. On the characteristic surface of the photomultiplier tube, the feedforward control function is the high voltage calculated from the photon count and the light intensity, and the function of the light intensity calculated by the photon count and the high voltage. Substituting the measured photon count and measured hight voltage into the light intensity function can calculate the measured light intensity. Substituting the measured light intensity and the preset photon count into the feedforward control function can calculate the feedforward compensation high voltage and feed it into the high voltage power regulator. The loop completes the feedforward control compensation of the photomultiplier tube. In addition to the photomultiplier tube characteristic compensation feedforward control loop, the feedback control can also be parallel connected with a PI linear feedback control loop to remove the effect of system identification model errors to let the measured photon count more similar to the preset photon count.
In order to calibrate and test the innovative airglow instrument design, this study also developed and constructed a photomultiplier tube calibration platform. The calibration platform can help the researcher to measure and establish the photon count corresponding to the light intensity characteristic curve. The calibration platform by an 10-fold optical attenuator to let the optical power meter can increase 10 time resolution to calibrate photomultiplier tube. This study proposed a preliminary validation of the simulation data, and then constructed the calibration platform, including optical, circuit, and software design. Finally, the calibration platform is verified by the experimental data, and the light intensity corresponding to the photomultiplier tube characteristic curve is established. By using the calibration platform, the photomultiplier tube characteristic compensation feedforward control algorithm with/without linear feedback control has been tested. The data shows that the new designed instrument can not only expand the linear dynamic range (Form 450 pW to 4500 pW) and but also increase the sensitivity (Maximum error is 1.69 pW, standard deviation is 0.73 pW). | en_US |