Appendix H Component Details – Standard Models
342
All other operating parameters, i.e. Lower Level Discriminator (LLD) and High
Voltage (HV), are software-adjusted using the control program's F2 – Test Menu, F8
– Discriminator Plot and F9 – Plateau Plot screens, respectively. Refer to the
previous Chapters.
Note: When an external LED/Detector ID Board is used to set the detector number,
all switches of SW1 should be in OFF position. This does not apply to the
GEM-5 monitor, which does not use LED/Detector ID boards.
Gamma Detector Board (SCN 816112)
The Gamma Detector Board Assembly includes:
• Gamma Detector Digital Board (SCN 816102);
• Gamma Detector Analog Board (SCN 816107);
• Mounting hardware.
The Digital Board is stacked on top of the Analog Board with the mounting bracket
in between. The whole assembly is mounted to the scintillator mounting bracket just
behind the PMT. The PMT assembly connects to the analog board by means of two
short (to minimize the noise pickup) cables, one for signal and the other for HV. Each
cable is equipped with a unique polarized connector.
Gamma Detector Digital Board (SCN 816102)
The Digital Board provides the following functionality:
• Detector Serial Interface Bus connectors, communication control logic (in the
FPGA chip) and line transceivers;
• Serial interface to the ADC and the DAC;
• Programmable voltage references for: HV, LLD, ULD and Test Pulser (quad
12 bit DAC chip);
• HV meter (based on the 12 bit ADC);
• Board Identification: the board number (from the on-board DIP switch
(normal usage) or from an external LED Board - if used - through connector);
• Local voltage regulators that provide stable +1.5V, +3.3V and ±5V power
(generated from the +12V interface bus power lines) needed for both Digital
and Analog Boards;
• LED indicators: Command LED flashes every time the board recognizes a
command sent from the Carrier Board; Alarm LED turns on when alarm
occurs on the corresponding detector or the board is selected during some
tests; Counts LED flashes every time analog board sends a pulse for
counting;
• Crystal controlled oscillator (24.000 MHz) that provides stable timing pulses
for the digital circuitry in the FPGA.
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