Precision chilled-mirror dew-point hygrometer and method for eliminating drift of measured temperature value

Abstract

Most chilled-mirror dew-point hygrometers measure dew-point temperatures by using platinum resistors; however, since platinum resistors have the defect of temperature drift, the measured values have certain difference from actual values. Therefore, correction with standard samples is required frequently. The invention discloses a precision chilled-mirror dew-point hygrometer with a temperature self-correction function, and a method for eliminating drift of measured temperature values. Before dew point measurement begins, two precision resistors R1 and R2 with resistances equal to platinum resistor resistances equivalent to upper limit and lower limit temperatures of the sample to be measured are used to substitute the platinum resistors, and are respectively and successively connected to a measuring circuit, and the measuring circuit is corrected. After the dew point is reached, the output voltage of the measuring circuit is recorded; based on the correction result, the drifted measured dew point value is converted into a standard value.

Description

technical field [0001] The invention relates to a precision chilled mirror dew point meter and a method for accurately measuring dew point temperature and eliminating temperature drift. Background technique [0002] The chilled mirror dew point meter generally consists of a dew point chamber, a refrigeration system, a photoelectric detection system, a temperature measurement system and a control system. The measurement principle and process are as follows: the sample gas flows through the condensation mirror in the dew point chamber, and the sample gas reaches a saturated condensation state through equal pressure refrigeration. The degree of condensation is determined by the photoelectric system, and the thickness of the dew layer is fixed by adjusting the refrigeration system through the control system. value; the temperature of the mirror surface measured by the temperature measuring system is the dew point of the sample gas to be measured. Therefore, the accurate determi...

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Problems solved by technology

For example, the difference in the purity of the platinum wire and the internal stress can cause the temperature drift of the platinum resistance temperature sensor to reach a few percent per year; the lead nodes in the measurement circuit will also produce thermoelectric potentials of different sizes due to the difference in the temperature of the environment due to the difference in material. , which in turn affects the accuracy of temperature measurement; and with the increase of the service life, due to the oxidation of the lead wire and the pollution of the circuit, there will be a certain degree of drift in the temperature measurement, which is the so-called "time drift".

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