Chromatography Forum

Dear All

I hope my question will not confuse people.

We have an OLD chart recorder which use pen. Recently the recorder can not use the full page (i.e., the pen stop moving upward whenever the absorbance is above 0.3, as a result, the peaks all look like a plaetau).

Because the recorder is too old, no one in the lab knows what could be the problem. W don't even know the model name of the recorder.

So I went online and found the following article:
http://caspar.bgsu.edu/~courses/HPLC/HPLCManual.html

The article says:
"ED LAB: The setup of the chart recorders is a story of it's own. The recorder dealing with the EC detectors displays the output of two channels, namely of detector 1 and detector 2. For both channels it is critical that the gain on the chart recorder itself is calibrated. Calibrate by using the calibration buttons for the two channels on the ESA detector module. For each channel, press the respective button and adjust the gain knob on the recorder until the trace is offset by approx. 1/10 of the width of the page. (Now never, ever touch this knob again!). To zero the trace set the channel on the chart recorder to calibration, put the trace where you want it using the horizontal adjustment knob and zero it with the zero button on the detector module, then set the chart recorder back to 10mV."

Suppose our chart recorder is the one described in the article and that you have ever used the recorder before, what do you think our problem is (recorder can not use the full page) ? How to fix the problem?

Thank you very much for your time!

Does the pen slide along metal rails or rods, and is it moved by string or thin wire cable ?

Try cleaning whatever the pen slides on. Also make sure that the string or wire is not getting jammed.

If that does not work and you cannot find a manufacturer's name anywhere on the chart recorder take a photo of it and post it here - maybe someone will recognise it.

Peter

Thank you very much.

The chart recorder, which is connected to a "waters 486 tunable absorbance detector", is the one shown in the picture below.

Suppose we want re-connect the chart recorder to the "waters 486 tunable absorbance detector", what step we should do to make the recorder work properly?

This recorder looks familiar, if I remember correctly the pen carriage rides on two guide rods and is pulled back and forth by a cable attached to a stepper motor. If you take off the top you can clean the guide rods, they probably have a buildup of material that is interfering with the movement of the carriage. The problem could also be with the stepper motor and cable, and with a unit that old parts may be hard to come by.

You have a dual pen recorder, so also check to make sure that the second pen carriage is not interfering with the movement of the first pen carriage.

I believe the zero adjustment range of this recorder is large enough that you may be able to move the pen the full range of movement, and that could help to determine the source of the problem.

I think Ron has helped you, but here are some further suggestions.

Look on the back of instrument - ensure you are connected to the suitable output ( normally most instruments that used chart recorders provided 0-10 mV or 1 V. ) .Confirm that your recorder is set to the same scale.

Disconnect the lead to instrument, and short the recorder input wires together. Use the zero adjust/offset knob for that channel to set it at 10% of the chart scale.

Then reconnect to instrument ( note that some recorders will drift up if leads are open circuit, don't worry about it or change the scale ).

Use the instrument zero/scale controls to see if the instrument readout and recorder output match ( being at 10% means you'll see negative movements ).

If they don't, then set instrument to zero readout, and reset chart recorder zero to 10 %, as above. Set instrument to 80-100% of reading. Then find the recorder span adjust ( usually set by default at 100% ) and use that to match instrument scale, using a value at 80-100% of full scale.

Please keep having fun,

Bruce Hamilton

Thank you

Finally it turns out some wire got stuck. Thanks for your suggestions.

Besides, does any one know where I can get a mannual of such recorder?

If my aging gray matter hasn't deceived me, I believe that you have a Linear brand strip chart recorder. These were often relabeled with a different brand name to go along with a set of instruments. A web search may produce more information. Good luck!

Thank you all very much!