Setting the Multiplier Voltage
When you acquire the multiplier gain curve (Auto EMS), the computer is
automatically setting the multiplier voltage. This voltage is displayed in the Pulse
Count Settings area of the Multipliers Properties dialog box. This procedure
also determines which input mode is used, pulse count (PC) or V/F.
As an example, you are trying to set a survey to 800K counts. For our
example, 800 is the V/F Setpoint (in thousands of counts per second, Kcps) and 1500
volts is the voltage in the Pulse Count Settings area of the dialog box.
- The analyzer goes to the highest kinetic energy in the range of the survey
(for example, if the survey is from 30 to 1030, it uses 1030). The analyzer will
set the multiplier voltage there because that’s where the highest counts are.
- The computer ramps the voltage based on the settings in the Gain Curve
Settings area of the Multiplier Properties dialog box. (The smaller the value of
V/Step, the more precisely the multiplier voltage will be set, but the longer it
will take to ramp the multiplier up each time.)
- Using the V/F Setpoint voltage for the acquisition type (this is also in the
Multiplier Properties dialog box), the computer ramps the multiplier voltage
from there to get 800K counts.
- If there is a lot of signal and you reach 800K counts at 750V, the system
acquires data in V/F mode because it reached the number of counts before it reached the pulse count voltage of 1500 volts.
On the other hand, if it gets to 1500 V (the pulse count voltage) before it
reach 800K counts, this indicates there isn’t a lot of signal. Therefore, the system acquires data in PC mode.
Note that the system will never go higher than the PC voltage.