Axon Axopatch 200B, Theory Of Operation

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56 • INSTRUMENT OPERATION
Axopatch 200B, Copyright 1997-1999, Axon Instruments, Inc.
Static Precautions
The headstage can normally be safely handled. However, if you are in a laboratory where
static is high (
i.e. , you hear and feel crackles when you touch things), you should touch a
grounded metal object immediately before touching the headstage.
You should not switch off power to the Axopatch 200B when handling the headstage input
since this will upset thermal equilibrium.
Optical Pick-up
The Teflon input connector and the glass walls of the hybrid package inside the headstage
are translucent. High intensity light can get through in sufficient strength to activate the
input transistors inside the hybrid. Therefore, you should prevent bright light from falling
on the input connector with a shade or by dimming lights. If you notice line-frequency hum
on the current record, it could be due to fluctuating light levels from a bright fluorescent
light or equivalent. In general, low light levels are not a problem.
Acoustic Pick-up
Rare instances have been reported where the headstage was susceptible to low amplitude
acoustic pick-up. The most troublesome being a situation where the audible hum of a
nearby isolation transformer was being acoustically coupled to the input of the headstage.
This was traced to the silver wire of the electrode and was solved by trimming off a
fraction of the wire, thus changing its resonant frequency.
Tuning the Headstage
See the
HEADSTAGE TUNING PROCEDURE
(page 121).