Apparatus for calibrating gas instrument

Abstract

The invention discloses a gas instrument calibration device, which comprises a calibration platform for assembling a flowmeter to be tested. The calibration platform is at least connected with a stagnation container, a sonic nozzle, a negative pressure pipe and a Roots vacuum pump adopting the variable frequency control in turn. The calibration platform and the gas inlet of the calibration platform are arranged in a lockable calibration chamber, and the gas outlet of the vacuum pump is communicated with the calibration chamber through an underground duct. The gas instrument calibration device which has the advantages of low noise pollution, low energy consumption and small error is particularly suitable for the calibration of a gas flow measuring instrument.

Description

technical field [0001] The invention relates to verification or correction of flow meter equipment, in particular to a device for verifying gas flow detection meters. Background technique [0002] Standard meter method There are many methods for flow standard devices, and the gas flow standard device using the sonic Venturi nozzle (or sonic nozzle) as the standard meter is one of them. Compared with using other flowmeters as standard meters, using sonic nozzles as standard meters has many advantages, such as simple structure, stable performance, high accuracy, no moving parts, easy maintenance, long verification period (five years) and so on. The sonic nozzle method gas flow standard device is suitable for the detection and calibration of various gas flowmeters, and can detect mass flowmeters, velocity flowmeters, volumetric flowmeters, rotameters, differential pressure flowmeters or other types of flow count. [0003] The structure of the traditional sonic nozzle method g...

AI Technical Summary

Problems solved by technology

The disadvantage is that when the gap between the required flow rate and the rated flow rate of the vacuum pump is large, the pipeline needs to be bypassed, otherwise the vacuum pump will also burn out

On the other hand, its pressure difference ratio is insufficient, and the highest foreign products can only reach 0.7 at present.

If the pressure loss of the verified instrument is slightly larger, the pressure difference ratio <0.85 at both ends of the sonic nozzle cannot be guaranteed, thus limiting the scope of use of the device

[0008] No matter which type of vacuum pump is used, the traditional gas meter verification device has one of the biggest and common defects: since the gas used for the verification is extracted from the outdoor atmosphere and discharged to the atmosphere, three problems arise. : One is that the temperature of the air extracted by the test cannot be controlled and is greatly affected by the outdoor temperature. Although it can be corrected by software, it brings additional errors in the correction calculation

The other is that because the air is discharged to the outdoor atmosphere, the noise is also taken out during the discharge, causing environmental noise pollution

Another one is that it is impossible to use frequency conversion technology

If the frequency conversion technology is used, for the gas ring vacuum pump, the decrease of the speed will make the pumping capacity of the pump drop rapidly, which cannot meet the verification requirements. For the water ring vacuum pump, when the speed drops, the average flow rate will be uniform The stability also deteriorates rapidly, which will bring uncertain factors to the test, which will cause errors in the test data and affect the authority of the test data.

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