Study Of The Key Technology In DC Nanovolt Meter

When spacecrafts are in testing, a lot of parameters are measured by voltage measurement. The outputs of some sensitive element in spacecrafts are low voltage signals. The measurement of direct low voltage is an important link of spacecraft's testing. Direct-nanovolt gauge is a meter of direct low voltage measurement. The key technology of low voltage signal measurement is studied in this article.The direct low voltage signal is a weak signal. The weak signal has low amplitude, and is in a state of tangled with noise. The background noise such as low thermoelectric, resistance noise, 1/f noise, is studied in this article, And the direct-nanovolt gauge can meet the need of design request in noise suppression.The direct low voltage signal has low amplitude, it is necessary to amplify the voltage, if we want to measure it. The conventional direct-nanovolt gauge employ modulation demodulation amplifier, which is an active amplifier. The modulation demodulation amplifier has a high input noise level, so the CCD-photoelectric amplifier is employed in this article. Different from the modulation demodulation system, the CCD-photoelectric amplifier is a passive amplifier. So the system noise of CCD-photoelectric amplifier is smaller then that of modulation demodulation amplifier. The CCD- photoelectric amplifier has a high sensitivity of nanovolt, and we can get a digital signal of voltage, when it is used to amplify the direct low voltage.The weak signal is in a state of tangled with noise, so a IFIR digit filter is designed in this article to improve the signal-to-noise ratio. Finally, another key technology of 20Bit digital-analogy converter based on PWM is studied in this article. The PWM digital-analogy converter has lower nonlinear scales and higher dynamic range then the digital-analogy converter in use.All these key technology guarantee direct-nanovolt gauge a higher resolution of 1nV then existing direct-voltage meter which has a resolution of 10nV. Direct-nanovolt gauge, together with standard source of the direct-low voltage, will establish unified standards of direct-low voltage measurement in the realm of national defense. It will play a important part in scaling a quantitative guideline about the measurement value of the direct low voltage, and will be helpful to improve the quality of Chinese spacecrafts.