Photoionization detector and method for dynamically adjusting range of detector

Abstract

The invention relates to a photoionization detector and a method for dynamically adjusting the range of the detector. The detector comprises an excitation power supply output module, an ultraviolet lamp, a pair of ion collecting electrode plates, an amplifying circuit and a feedback control circuit. The input terminal of the excitation power output module is connected with a direct-current power supply; the output terminal of the excitation power output module is connected with an excitation electrode of the ultraviolet lamp; the pair of ion collecting electrode plates is arranged in an ultraviolet light emitting direction of the ultraviolet lamp, the electrode plates are connected with the input terminal of the amplifying circuit, the output terminal of the amplifying circuit is connectedwith the input terminal of the feedback control circuit, and the output terminal of the feedback control circuit is connected with a control terminal of the excitation power supply output module. With the excitation power supply output module and the feedback control circuit, the detection precision and sensitivity are optimized according to the concentration range of the to-be-detected gas.

Description

technical field [0001] The invention relates to the technical field of detection, in particular to a photoionization detector and a method for dynamically adjusting the range of the detector. Background technique [0002] A photoionization detector (PID) is composed of a vacuum ultraviolet lamp, an ionization chamber, an ion collecting electrode, and an amplifier circuit. The working principle of PID is: the gas to be measured absorbs the photons emitted by the ultraviolet lamp that are higher than the ionization energy of the gas molecules to form charged ions, and the ions migrate under the action of an external electric field to form a weak current. At present, the optional values ​​of ultraviolet light energy are 9.6eV, 10.6eV, 11.6eV, etc., among which 10.6eV is the most common, which can ionize most organic vapors and some inorganic gases. In the amplification circuit, the weak current generated is generally amplified into a voltage value that can be easily measured b...

AI Technical Summary

Problems solved by technology

In the case of the same circuit, small range often means high accuracy and high signal-to-noise ratio, but too small range will be saturated when measuring over-range gas, so that accurate concentration cannot be obtained

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