Techne Gene E thermocyclers

Dr. T.E. Cullingford tculling at
Thu Nov 24 13:59:06 EST 1994

We have recently purchsed two of the above machines, without heated
lids, from Techne. I have found that, using an external thermistor
placed in mineral oil in a 0.5ml PCR tube, that there is a lag between
the thermocycler display showing that it has reached a certain temp. 
(eg. 94oC) and the thermistor display. This means that if one has set 
the hold time at 60 seconds, for example, the thermocycler begins to
count down from 60 secs. when the display reaches 93.5oC (which is as
I expect), whereas the thermistor only registers this temperature with
as little as 10 seconds remaining on the hold time. More disturbingly, there is variation in the lag between my two macines and another possessed
by a colleague. If from time to time a PCR reaction fails I must consider
whether this lag is a possible explanation. Have others found similar results
with external thermistors, or can offer rational explanations?

Tim Cullingford

Institute of Neurology
Queen Square
London WC1N 3BG, U.K.

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