Multichannel Systems STG4004+STG4008 Manual - Manual (Page 100)

Stimulus Generator 4000 Series Manual
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12.4 Signal terminated when using Trigger In
If you use the Trigger In to start the STG and the stimulation protocol is terminated right after
start, check the Trigger Settings. If the Use Trigger as Gate function is selected, a protocol will
only be active as long as the Trigger is HIGH. If the Single Trigger function is selected, the STG
is armed and waits for an external trigger to execute the stimulus protocol one time only.
Switch to Stop, Restart or Ignore.
12.5 Strong Peak Artifacts
Strong discharges or other artefacts of the output voltage or current.
Possible causes:
? One or both current outputs are open, that is, nothing is connected to them. The stimulus
generator tries to hold a stable current against the indefinite resistance of the open current
output. Therefore, the stimulus generator will increase the output voltage on the open current
outputs to its maximum, which will result in a heavy load on the power supply. This situation
may cause the power supply to become unstable, which may lead to artifacts on all channels.
 In current mode: Connect the unused current output to ground (GND). Please see also
the recommended setups in the chapter “Current Mode”.
12.6 Output Signal Does not Match Programmed Signal
The amplitude or the duration of the output pulses differs from the programmed signal.
Possible causes:
? The stimulus protocol works near the resolution limits of the STG, that is, the pulses are very short
or the amplitudes very low (smaller than 50 mV or 10 μA).
 Check the output signals with an oscilloscope and modify the pulse protocol so that the amplitude
and timing of the pulses will match your requirements.
? You operate the STG in current mode, and the electrode resistance of the stimulating
electrodes is too high. According to Ohm's law, the electrode resistance directly affects the
kinetics of the current output. The rise time increases with an increasing electrode resistance. If
the electrode resistance is too high for the compliance voltage, the output signal will be clipped.
 Try to stimulate in voltage mode.
 Try to use stimulating electrodes with a lower impedance.
 Check the output signals with an oscilloscope and modify the pulse protocol so that the amplitude
and timing of the pulses will match your requirements.