| Gas meters are one of the six key management of measuring instruments constrained in mandatory verification imposed by China and widely applied to domestic,industrial and commercial fields.As production license of gas meters is abolished,the position of pattern evaluation of gas meters is increasingly important.Moreover,the temperature adaptability test is an important component of pattern evaluation items of gas meters.Therefore,offering a temperature adaptability test device for gas meters and carrying out high-low temperature test have great significance.In this article,the temperature adaptability test device for gas meter is designed based on non-isothermal measurement method.A root flowmeter or wet gas flowmeter is selected as the standard meter.The tested gas meter and the standard meter are connected to each other which are placed separately inside and outside of the thermostat respectively,then converting the gas volumes of both the tested gas meter and the standard meter measuring are corrected and compensated automatically by temperature and pressure to the same conditions for comparison,and finally obtaining errors of indication of the tested gas meter.The test of the temperature adaptability for diaphragm and ultrasonic gas meter is carried out based on the device.The main research contents and contributions are showed as follows:(1)A means to simulate gas meters work at actual ambient temperature is researched.The temperature adaptability test device for gas meters is designed,which is composed of a condenser,a dehumidifier,a thermostat,a heater,a heat exchanger,three standard meters,two variable-frequency fans,etc.Tests have demonstrated that every technical performance index of the device can reach the predetermined design goal.The expanded uncertainty of the facility is better than0.3%(k=2).The device can be applied to the test of temperature adaptability for gas meter.Its applicable flowrate range and temperature range are(0~16)m~3/h and(-40~60)?respectively.(2)The test of flowrate measurement of domestic diaphragm gas meters with different use ages has been performed at different temperature conditions.The influence of temperature on their metrological performance has been analyzed and a few of mathematical models based on the method of data dimensionality reduction assessing the relationship between indications measured by diaphragm gas meters and actual gas supply from gas companies are offered.(3)The temperature characteristic of ultrasonic gas meters has been tested and the influence of flowrate and temperature on their metrological performance has been analyzed.The results showed that the metrological performance of ultrasonic gas meters at high flowrate was much better than that at low flowrate.The relative error and repeatability of ultrasonic gas meters deteriorated as the temperature deviated from the reference temperature of 20?. |
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