Neurotechnology Research Systems
© Plexon Inc
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Once the parameters for a channel have been loaded you may start the stimulation by clicking on
the “start” button:
The stimulation begins, and because the number of repetitions is set to infinite, the pulses will
continue until the “Stop” (or “Edit”) button is pressed.
5.5
Verifying the output on an oscilloscope
Now examine the current and voltage waveforms on an oscilloscope to see if they make sense. Note
that both the current and voltage monitors output a voltage signal and that there is a scaling factor
that relates what you see on the monitor output to what is happening at the electrode. The scale
factor for the current monitor is 2.5 mV/µA and by default the scale factor for the voltage monitor is
0.25 V/V. That means that if there is a 100 µA current flowing into the electrode from the
stimulator, the current monitor will read:
Likewise, if the stimulator was applying 1V to the electrode, the voltage monitor would read:
The current monitor waveform you see should appear similar to the figure below:
At the beginning of the pulse, the current monitor (I
MON
) jumps from 0 mV to +250 mV and stays at
+250 mV for 50 µs. Then the current monitor drops back to 0 mV for 25 µs and finally drops to
−250 mV for 50 µs. Considering the 2.5 mV / µA scaling factor on the current monitor these 250 mV
steps represent current steps of 100 µA as expected from our channel configuration settings. The
durations also match our settings.
50 µs
50 µs
25 µs
+250 mV @ I
MON
= +100 µA @ electrode
–250 mV @ I
MON
= –100 µA @ electrode