Functional
Description
ComTec GmbH
3-1
3. Functional
Description
3.1. Introduction
The 7072T has three different modes of operation:
•
PHA: Pulse Height Analysis
•
SVA: Sampling Voltage Analysis
•
TDC:
Time-to-Digital
Conversion
Any channel can be set in any mode of operation independently.
All settings of each channel are done via push buttons on the front panel. In normal operation the
range and conversion gain are set using the corresponding UP/DOWN push buttons of each
channel. To change any voltage level or the GATE mode from coincidence to anti-coincidence
pressing the MODE button will switch into the adjustment mode indicated by the ADJUST LED lit.
Now the corresponding voltage level is changed by the UP/DOWN buttons. Subsequent pressing
the MODE button cycles through the different adjustments until you are back to normal operation.
3.2. Modes of operation
3.2.1. Pulse
Height
Analysis
In this mode of operation both channels accept analog input signals between 0.025 and 10 V and
measure the peak amplitudes that are higher than LLD and lower than ULD thresholds. Outside
of that range between LLD and ULD there is no conversion.
To prevent triggering from noise and to adjust for small input offset voltages an ADC threshold is
settable in the range of –100 mV … +1.0 V. The default value is +20 mV. PHA is triggered only
when the input signal rises over this ADC threshold. A subsequent conversion is enabled only
when the signal has been fallen under this threshold again. Thus, pile-up rejection is provided.
When adjusting the ADC threshold it "pushes" the LLD if reached. Thus, the LLD level is always
greater or equal to the ADC threshold.
3.2.2. Sampling
Voltage
Analysis
In this mode of operation the corresponding channel accepts analog input signals between 0 and
+10 V and measures the voltage when the GATE signal goes low to high in coincidence and high
to low in anti-coincidence mode. In the SVA mode of operation, if the analog input voltage to the
ADC is outside of the normal 0-10 volt range (exact range may vary slightly from unit to unit), the
converted digital output will be channel zero if the voltage is greater than the normal range, and
channel 8191 if it is below the normal range (firmware version V84 starting Feb 2007). The
firmware version and date can be found on a label at the backside of the 7072T board.
