Air inlet flow stabilizing device for portable FID (Flame Ionization Detector)

Abstract

The invention discloses an air inlet flow stabilizing device for a portable FID (Flame Ionization Detector), which comprises an air resistor, a pump, a sensor and a controller, and is characterized in that the air resistor is used for limiting the flow rate of air; the pump is an air pump and is used for feeding air into the FID detector; the sensor is used for detecting the air pressure difference between the two ends of the air resistor; the controller adjusts the voltage of the output pump according to the air pressure difference detected by the sensor and controls the rotating speed of a motor of the pump. Gas passes through the gas resistor and is fed into the FID detector through the pump; and the sensor and the controller form a feedback loop. The method can be applied to normal-pressure detection conditions, so that the flow control is more stable, the realizability is high, and the cost is low.

Description

technical field [0001] The invention relates to an air intake stabilizing device, which is suitable for the intake stabilizing flow of a portable or mobile FID detector. Background technique [0002] Hydrogen flame ionization detector (Flame ionization detector, FID) is a common sensor used to detect volatile organic compounds in the air. It uses a hydrogen flame to ionize volatile organic compounds (VOCs) to generate hydrocarbon ions, and the ions move in a directional manner to form an electric current, thereby measuring the concentration of organic compounds. FID needs three kinds of gas sources: gas, supporting gas and measured gas; and the gas needs to be sent to FID in proportion. [0003] Common FID intake air flow stabilization devices mainly have the following two methods: [0004] The first method adopts the method of high voltage step-down and steady flow. An electronic pressure control (EPC) module or a mechanical steady flow device is added to the pipeline, s...

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Problems solved by technology

[0006] Both of the above two methods have disadvantages. The first method of high-voltage step-down and steady-flow is suitable for occasions with positive pressure gas input, and the cost is relatively high; the second method of double-pressure step-down and steady-flow has two disadvantages. One is The lack of closed-loop control of the pump will cause the gas flow rate in channel one to be unstable, thus affecting the gas flow in the pipeline; second, the input pressure of the gas entering channel two must be greater than the pressure of the entire pipeline, otherwise the gas flow in channel one will The gas will be injected back into channel two

These two devices have requirements on the input pressure of the gas, and require many parts. They are suitable for large-scale or online detection equipment; they are not suitable for portable or mobile detection equipment.

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