Fixing BAK Electronics IMP-2 Electrode Impedance Tester

BAK IMP-2 Tests a 1MOhm Resistor, declares impedance to be 1MOhm. 

In getting ready to do some electrophysiology I fixed up a broken a BAK IMP-2 Electrode Impedance Tester.  This unit measures impedance at 1kHz.  The device I got was given to us free in a broken state.  My guess was that some op amps got fried by a "naughty" experimenter.  This was indeed the case, however, not one, but two op amps were destroyed.  The unit runs off of two LF442CN dual op amps and one OPA111A high precision op amp.  The burned out components were the OPA111A and one of the LF442CNs.  Lucky for me, we found replacements for both components the same evening and the unit is now as good as new!  I must thank my awesome tech for helping me verify the broken op amps and find replacements! Ready for electrodes.

Sniffs and Spikes

My next technical challenge in the lab is to set up simultaneous recording of sniffing and of neural spikes.  I am planning on putting together a compound device integrating a silicone probe for measuring neural activity and a pressure sensor for measuring sniffing simultaneously.  The trick will be to have all inputs and output go through a single tether wire.  Currently my thinking is that I can use a TDT ZIF-Clip with 64 channel capacity and use 32 of the channels for the electrodes and 4 channels for the pressure sensor (+V, -V, Gnd, Out).  For a commutator, I am thinking of getting a 36 channel slip ring system from the orbex group.

UPDATE:  Turns out there are issues with integrating other inputs/outputs into the ZIF-Clip from TDT.  Currently, the clip uses nearly all of its channels for electrode signals and it is difficult to break any channels out.  My alternate solution is to just put up with a second (third) wire to the head and continue attaching the sniff sensor via a magnet.  We are now miniaturizing our sniff sensor so that it may fit better on the head alongside the electrode and micro drive.