FID Signal Fluctuation

Hey guys,

I noticed that my FID Signal (6890N) started fluctuating and deducted that the signal fluctuation corresponds with a fluctuation of the H2 Gas Flow for the FID.

Has anybody had this problem before? Is the FID leaking? Might the PCM Module for the FID be broken ?

Thanks for the help

  • Hello  ,

    Since the FID baseline is reacting to the pressure fluctuations in your H2, it is more likely for you to have a contaminated gas source. At least that is my assumption right now.

    What is your baseline usually at, when you are not running samples? And is your H2 source a tank or a generator?

  • Hi,

    My baseline is around 8pA in standby state. H2 is coming from a tank and I can rule out contaminations in the gas source because the gas line is splitted with T piece: one is going to the FID EPC and one is going to the inlet PCM. H2 is the carrier gas. I monitored the H2 front inlet pressure during samples and it doesnt show any fluctuation at all (as it should be). Thats why im afraid the FID EPC has a problem :/

  • Hello ,

    Well, in this case I'd say maybe PCM is having a problem. The way I see it, signal spikes can either come from either an electronic issue or contamination. Since in your case the baseline increases and decreases along with H2, I assumed H2 tank/lines are contaminated. It definitely doesn't look like an electronic issue.

    I couldn't be too sure what is going on here, but PCM could be a potential problem. Whether or not it is the reason for the baseline spikes, I feel like the pressure bumps shouldn't be present; maybe a valve in the PCM is sticking or somehting.

  • ill try changing the pcm module to see if that resolves the issue.. i see no reason where any contamination comes from (we have a lot of other gcs using the same h2 tank and none show this signal behavior) so i believe its a electronic problem.. sigh.. im running out of spare parts for 6890 gcs.. thanks for the suggestions

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