Service manual

LUMISCAN ACR-2000 SERVICE MANUAL - SECTION 4.0 THEORY OF OPERATION
4-3
4.4 Digital and Electrical Systems
The electrical subsystem of the LUMISCAN ACR-2000 READER consists of the Data Control Board,
(DCB), that is located in a PC-type host computer an interconnecting cable to the LUMISCAN, and the
scanner, which houses six printed circuit boards. These include:
Data Acquisition Board (DACQ),
PMT PreAmp Board,
Galvanometer Board,
Indicator Board.
Indicator/ff Interface Board
Reference LED Board
4.4.1 Data Control Board
All operations are controlled by the Data Control Board via means of control registers. Although some of
these registers are physically located on the Data Acquisition Board, they are accessed through the Data
Control Board. Once a scan is initiated, data acquisition is automatic, requiring no intervention until the
image has been written into image memory on the Data Control Board. Image data can be transferred out
of image memory during or after image acquisition. The Data Control Board receives its power from the
host computer. No power is transmitted over the interconnect cable.
4.4.2 Data Acquisition Board
The Data Acquisition Board performs all the signal conditioning and data acquisition functions, including
calibration and lookup table functions.
4.4.3 PMT PreAmp Board
The PMT PreAmp Board contains the first stage preamplifier. This board provides power connection, a
high voltage divider network for the PMT tubes and a first stage amplifier for the PMT signals.
4.4.4 Galvanometer Board
The Galvo board contains a high-accuracy feedback servo amplifier for controlling the position of a mirror
mounted on the shaft of a scanning galvanometer. Position feedback is from a sensor integral to the galvo.
The galvo motor shaft oscillates back and forth through an arc of approximately 30 degrees at a rate of
50Hz. A small mirror attached to the shaft intercepts the static laser beam and sweeps (scans) it across the
width of the image plate. It important that the Galvanometer Board be adjusted so that the beam scans
across the plate at a consistent speed. Proper performance of the Galvo PCB is dependent upon the
adjustment of several of its potentiometers.