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Topic: Gilson pipette with reverse error  (Read 171 times)

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Offline pcm81

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Gilson pipette with reverse error
« on: May 27, 2019, 05:35:23 PM »
I bought a used Gilson-P1000 pipette on ebay. Supposedly refurbished and calibrated. When i am testing it with DI water i am seeing a reverse error. At 1000uL setting i actually get about 1.01 grams, so its 10ul off. At 100ul i get 140 milligrams, so it is over delivering by 40ul. In between volumes follow this pattern. Bigger absolute error with smaller volume. Normally i'd expect to see bigger error with bigger volume or a fixed offset error. Anyone can give me some ideas of what i might be dealing with?

Thanks

P.S. The frustrating part is that i can get more accurate transfer using a glass 2lm pipette with pipette pump, which this gilson was supposed to replace.
« Last Edit: May 27, 2019, 06:03:28 PM by pcm81 »

Offline pcm81

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Re: Gilson pipette with reverse error
« Reply #1 on: May 27, 2019, 06:29:00 PM »
I know you not supposed to go below 100 im P1000, but mine adjusts all the way to 0 and below 100uL i get a consistent 40uL error. Delivered 50ul at setting 10uL etc.

Offline pcm81

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Re: Gilson pipette with reverse error
« Reply #2 on: May 27, 2019, 09:21:31 PM »
This seems to be an old version of pipette. After tinkering with it for a bit i found a way to adjust it, but still not perfect. Sharing my findings for the benefit of others. This is an older version with SN: L16004J.
This version does not have screws holding the adjustment wheel, but rather the top of the pipette, the back of the wheel has a nut that unscrews. The depth to which this nut is set controls the travel of the plunger. Theoretically it should be an offset adjustment, not slope. There are no set screws holding the nut in place, so turning it you adjusting it.
After tinkering with position of the nut i determined that any position other than real tight, which is how it was, makes things worse. The thinned down portion of  the plunger goes through the center of that nut and that nut determines plungers travel distance. The piston, which is what actually doing the fluid evacuation is moved by this plunger. I added a 3mm washer to the back of the nut to push plunger forward. This addition has made things better but i am still dealing with slope error. Before adjustment i was 22ul over at 1ml and 40ul over at 100ul. I am now 15ul under at 1ml and 10ul over at 100ul.

Hope this helps to anyone else that is trying to calibrate Gilson P-1000

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