GC TCD detector troubleshooting - gas chromatograph, detector - Education Industry

Published: 03rd March 2011
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1, the bridge current fault The TCD carrier gas through the premise, open the bridge current switch, current control knob for adjusting the bridge. Bridge current should be transferred to a predetermined value stable. If the adjustment is not found in current tune up, especially the thermal conductivity cell at high temperature, the current adjustment less than the maximum rating of the bridge, the bridge can be considered to be less than current book value of transferred fault.



Such malfunctions are the following: thermal conductivity unit not connected to the connection; thermal conductivity of the pool open hot wire disconnected or lead; bridge Power Supply Faulty; bridge configuration circuit disconnect or current meter is faulty.



2, the baseline zero fault Bridge current transfer good and stable, respectively, zero adjustment of the thermal conductivity of the knob, so that the baseline on the recorder instructions back to zero. If you adjust the knob, no matter how, no change or adjust the baseline are less than zero is considered to have zero thermal conductivity of failure.



Zero thermal conductivity can not fault the following causes are several: hot wire resistance, or lead a wrong asymmetry; hot wire into a wall, or serious pollution; zero potentiometer lead open circuit; Recorder Open or no response; Double Air Road traffic by very much.



Thermal conductivity can not rule out zero failure, according to the following steps:

(1) attenuation block test: the discovery of a baseline shift relative to zero, it will decay from the small to the largest block adjustment to observe whether the gradual reduction of deviation from the baseline.



(2) the role of zero knob check: each spin of brute force, in small knob, observe whether the baseline response.



(3) two-way flow check: In the gas line leak testing based on the use of soap film gas flow meters were tested two-way flow of value, see if that much difference.



(4) between the hot wire resistance error check: on the hot wire thermal conductivity cell levels socket for terminal resistance Measure. In general, the resistance group the difference between the hot wire should not be



0.2 ~ 0.5 , as beyond this value, shall be (6) treatment.

(5) hot wire into a wall or smear: hot wire hot wire into a wall and by measuring the insulation resistance between the cell body to be confirmed. Hot wire of a serious stain on the thermal conductivity cell by cell body



Cleaning and removing or part of the elimination of the specific steps to see the cleaning of a detector.



(6) hot wire or lead a wrong asymmetry: This usually occurs in the repair of thermal conductivity cell circuit, the experience of such situations need to carefully check the connection between the hot wire pinout. Correct



The hot wire connected in the four form a bridge, and bridge the two arms of the heat on just the same air route.



(7) two-way traffic by very much or pneumatic leak treatment: two-way flow of difference is too large can be controlled by adjusting the pneumatic valve to be resolved, but this time there should be two vent gas line



Leakage. (8) open-zero circuit. (9) recorder open or no response.

3, the baseline noise and drift

Cause instability in the baseline thermal conductivity detector are many reasons, some dozens of species common are:



(1) power supply voltage is too low, or fluctuations in the power load on the same phase change too much;





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