| 摘要 |
<p>In atomic spectrophotometers comprising a source of radiation characteristic of an element to be detected in a sample, monochromator for selecting a desired spectral line from radiation received from the source via the sample, and a detector for producing an output signal from the monochromator output radiation, the monochromator must be accurately tuned to the desired line to obtain a maximum detector signal and simultaneously the gain of the detector must be adjusted to keep the signal magnitude within the best working range of subsequent signal processing circuits. In accordance with the invention both adjustments are made simultaneously by comparing the amplified detector signal S, B with a desired reference signal level RV corresponding to the best signal magnitude and using the difference between them to adjust D the gain of the amplified detector signal in a closed loop control system to equalise the amplified detector signal with the reference level continuously. The monochromator 13 is tuned, preferably by automatic means MCP, 32, 20, to seek a minimum value of amplifier gain, at which the detector output will be a maximum at the peak of the spectral line, the amplified detector output being simultaneously equal to the desired reference level. The amplifier gain is then set to the value so obtained via DAC and absorption measurements made with the control loop open (RUN).</p> |
