HP5890 FID signal output problems

[www_ups]

hi all,
I am trying to setup an old 5890 for my research. I bought a peaksimple data board and hooked it up to a computer (with all the drivers properly installed) and the analog signal detector port of the GC. My problem is that when the FID is lit, it displays the signal properly on the machine, but on my computer, it still shows the signal to be zero. I tried injecting some acetone down the column to see if the databoard is able to pick anything up, with no improvement. I then troubleshot the databoard by connecting a 1.5V battery across the inputs; it reads 1.3 V (properly). The wires were checked for continuity and all turned up ok.
So, I am not able to get a signal from the GC detector pins to the databoard. I believe I am connecting the pins properly. Can anyone tell me how to troubleshoot this?
Thanks.
p.s.I am using the following pin ordering to connect my analog cables:
12 11 10 9 8 7
1 2 3 4 5 6
(The pin number assignments are as given in the HP manual, pg #APPXA-7).

[Peter Apps]

It is some time since I used Peak Simple, but I remember that you have to select the channel that is displayed on the screen - if you have the wrong channel selected it looks as if there is no signal. Also it has a huge range of sensitivity / attenuation settings that can make a signal disappear completely if you have them set too high.

Peter

[www_ups]

It is some time since I used Peak Simple, but I remember that you have to select the channel that is displayed on the screen - if you have the wrong channel selected it looks as if there is no signal. Also it has a huge range of sensitivity / attenuation settings that can make a signal disappear completely if you have them set too high.

Peter

Peter,
Thanks for the reply. I think I have the correct channel displayed on screen with appropriate sensitivity/attenuation ranges. ( I see a 1.5 V signal on the computer when I connected a AA battery across the databoard instead of the GC). Instead, I see random noise when I plug the analog cables to the GC. That is why I think that this is a problem with the GC rather than the DAQ system.

[AICMM]

www_ups

Which pins of the signal cable are you connecting to the Peak Simple data +/- points on the board? Also, have you made sure that you have assigned the proper signal to the proper output connection. Meaning, if the detector is in the A slot and the signal cable is connected to Signal 1 pins, you have to tell Sig1 = A.

Best regards.

[www_ups]

AICMM,
Thanks for the reply. I am connecting pins 4,6 or 7,9 to get the 1V signal out. When I do this, I get a constant voltage of 1096 mV. This signal (observed on the computer) does not change even when I shoot some acetone through the FID (though the numeric display on the GC indicates the FID peak) . I got the pin assignments from the Agilent website: http://www.chem.agilent.com/cpdocs/a15966.pdf
Regards

[AICMM]

www_ups,

Looks like you are using the correct pins assuming that Pin 2 is towards front of GC and towards the oven. I have an analog signal cable configured the same way. However, the fact that you have 1065 mV at the output suggests a different problem. That means the electrometer is "pegged out" and putting out the maximum signal. You either have a very unhappy detector or an electronics problem. What is the signal on the keypad?

Also, a bit perplexing is that the Peak Simple does not see the 1065 mV unless you zeroed it and all it is seeing is 1065 all the time which would explain why no response. Disconnect signal cable from PeakSimple, zero PeakSimple and re-connect to see if it picks up the 1065 (it should based on what you have said so far.)

Best regards.

[www_ups]

AICMM,
Thanks for the inputs. The signal on the keypad (when the FID has been working for 2-3 days) is ~500. I might need to clean the FID jet to get rid of the residual signal. Peaksimple does see the 1065 mV signal even without zeroing it. Are there any other means to test the electronics on the GC?
Thanks,
www_ups

[AICMM]

www_ups,

You do indeed have an unhappy FID if it is showing about 500. Should be well under 50. Having said that, you can cheat for a bit and see what it does to the signal at PeakSimple. If you set the zero for signal A at 450 or so (punch the value in on the keypad after you hit the zero button), it should electronically offset the output to the PeakSimple and get it back on scale. You can also use the range setting for the detector to divide the signal output and get yourself back on scale. If either of these do the trick, you will have a very limited working range but it should output real signal.

It would be better to find the reason for the high standing current on the FID, dirty gases, dirty collector, column bleed, carryover, injector bleed, whatever, than to play with the signal conditions to force it to work. From your comment, it sounds like the FID starts even higher than 500 and goes down with time?

Best regards

[www_ups]

AICMM,
Thanks, the FID signal starts ~45000 or so before it comes down to ~500 (with the oven being baked @ 200 C). It looks like a dirty jet might be causing this. Will clean the detector soon..
Regards

[www_ups]

AICMM,
I got the FID cleaned and the signal now shows 8 mV. (The fid was dirty and had some rust). I can see peaks from injecting acetone on my computer. Thanks for the guidance.

I have to depress the ignitor to keep the flame lighted, is there a way to troubleshoot this?

Regards

[AICMM]

www_ups

Good to hear your signal is better. Regarding flame ignition, your flows are probably wrong. If you are using HP's bizarre four way flow controller, this really means that your cylinder pressue for the air and hydrogen are wrong since the pressure sets the flow. Look in the manual for proper flow rates and adjust your cylinder pressure until you get the flows you need. Should work fine then.

Best regards.