A way to step up 30uV-300uV to 1mV+?

So I'm working at a TV repair shop but really we fix and work on almost anything electronic. In this situation we have a NEUROSIGN 100 which is used to tell the surgeon when he's near the nerve, but he needs the voltage spike to be recorded on paper when he touches the nerve. The problem is that the machine only gives out around 30uV-300uV as he is working and the electronic ghraph we have only startes recording at 1mV. We need a way to step up that voltage coming out the machine so that ghraph will record it. We tried a small audio amplifier but that didn't work at all so we're back to the drawing board.

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This thing has a bargraph output, thats a LOT more than 30-300uV. Use the input to the bargraph.

Really, if you have to ask this kind of question, you really, really shouldn't be messing inside a piece of neurosurgical test gear.
Jimmy Proton (author)  steveastrouk5 years ago
We have to work with the output coming from the back, were just trying to find a way to step up the voltage for the graph to read.
Show me some pictures of the thing.

The safest place by far is to pick off the bargraph signal, and even then, I'd use an isolation amplifier.
Jimmy Proton (author)  steveastrouk5 years ago
We want to record channel 1 & 2. The graph has a red and blue pen that will show the results on paper. I'm not sure my boss wants to open this thing up and poke around but I'll be sure to pass on the idea(:
You need a gain of only between 3 and 30.

Use a Burr-Brown (Now Texas Instrumetns) ISO122 and ISO 150 and you have all you need. The datasheet has some clever circuits http://www.ti.com/lit/ds/symlink/iso122.pdf
Jimmy Proton (author)  steveastrouk5 years ago
MY boss was able to get it to work somehow but thanks anyways(:
Which channel are you intending to monitor ? The EMG or the stimulation current record ?
-max-5 years ago
You can get an amplifier and amplify the voltage. That is your only option