Boiling cycler nightmare

Dr. Duncan Clark Duncan at
Wed Aug 16 10:47:56 EST 2000

In article <160820001549122963%jpcd100 at>, John Dixon
<jpcd100 at> writes
>So far the only accurate temperatures we can think of to test our
>thermocouple with are:
>37C using waterbath with medical thermometer
>100C boiling water bath
>Anyone got any cunning ideas of any other defined temperatures to check
>our thermocouples accuracy?

You will need a very fine thermocouple else the wire actually pulls heat
from the 50ul of liquid you have in your microtube so it measures wrong.
You will need a mineral oil overlay as well to stop evaporation. It's
also not so much (I think) the accuracy of the thermocouple as the
accuracy of the meter it is attached to. If I remember rightly the
thermocouple's voltage is constant due to the dissimilar metals and the
change in voltage per degree and voltage at a set temperature should be
identical for every manufacturer's thermocouple's. 

I would test the thermocouple meter calibration in boiling water, ice
water and how about liquid nitrogen? 

How come the orange dye is getting across the wells? That would suggest
(apart from possible boiling) that the well seal is leaking? Can you
eliminate the problem being poor plastics?

On machines we run 9700's and 2400's and touch wood, haven't had

Good luck

The problem with being on the cutting edge is that you occasionally get 
sliced from time to time....

Duncan Clark
DNAmp Ltd.
Tel: +44(0)1252376288
FAX: +44(0)8701640382

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