GBS Elektronik MCA 166 - Manual (Page 34)

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Enter the time per channel. Minimum step: 10 msec.
Maximum value: 500s.
The calculated total measuring time is then shown below the time per channel setting.
Input Type (MCS mode)
Use the spacebar to select between "extern TTL" (pulses), "Input Rate" (from the count
rate meter) or LLD/ULD (Only impulses between the LLD/ULD limit are counted). Default
is TTL.
3.4.2.4 Amplifier setup (not available if input set to TTL)
This submenu can only be activated if input Type (see 3.4.2.3) is set to LLD/ULD or input
rate.
Allows to setup the amplifier parameters like gain, shaping time, input polarity and pole
zero cancellation (PZC). PZC and gain can also be adjusted using a graphic screen to
support fine tuning.
Coarse gain
Use the space bar to select the value for the coarse gain (2-1000).
Fine Gain
Input the value for the fine gain (0.5000 - 1.5000).
Do visual gain adjustment
Press Enter to switch to a graphical screen with the spectrum. Use the screen to adjust
the fine gain while observing the spectrum. If the cursor is currently in a ROI then the
peak centroid will be shown. This is useful to do some coarse calibration, e.g. adjust fine
gain in a way that 1 channel corresponds to 0.5 keV energy using a germanium detector.
Shaping time
Use the space bar to toggle between the two time constants 1 and 2 microseconds. Use 2
microsec for low countrate measurements with a HPGe detector where the best
resolution is needed and 1 microsec in all other cases.
Input polarity
Use the spacebar to toggle between amplifier input pulses with negative or positive input
polarity. Remember: Wrong polarity is a common reason for measuring strange spectra or
getting no signal at all.
PZR Mode
Is always “manual”. Only in WINMCA there is a automatic option.
Adjust PZC now
Press Enter to access the graphical screen which visualizes the pole zero adjustment. For
adjusting PZC a count rate of 1000 - 10000 should be optimum, and the majority of these
pulses should fill the measurement range at least to the half. The bar indicates the
voltage at the ADC 8µs after the pulse peak maximum. This voltage should be adjusted to
zero. A wrong PZC setting may lead to a degraded resolution.