6. Component Functions and Parts
This chapter provides a detailed description of the functions of the
main components of the QA-ES, as well as a parts list for cross-ref-
erence. Reference is made to the component location and schematic
diagrams to assist servicing personnel. These diagrams are foldouts,
and are located in Appendix B.
6.1 Processor Board
(Refer to QA-ES Processor Board Component Location Diagram
and Schematic Diagrams 1 and 2) The Processor Board is installed
on the inside of the front plate. It comprises the:
power supply;
microprocessor system;
display;
function keys;
interface towards Sampling Unit, and;
RS 232 port and printer port
The Processor Board activates and controls the sampling procedure
in the QA-ES. The data is routed back from the Sampling Unit to
the microprocessor, where the results will be calculated before being
displayed.
1. Power Supply
(See QA-ES Processor Board Schematic Diagram 2). The Pro-
cessor Board receives 12 VAC from the Transformer located at
the rear of the QA-ES via J4. The voltage is then converted with
diode D9 and filtered through C1. Voltage regulator U8 sup-
plies the circuits with +5 V. The voltage is adjusted with resis-
tors Rl0 and R11. Schottky diode D4 protects the 5V power
supply to the printer interface to avoid any power flow between
the printer and the Processor Board while the QA-ES is
switched off. Capacitive switch regulator U9 generates -12 V
from +12 V. V-comparator U10 monitors the +5V voltage and
sends a reset signal to the microprocessor when the voltage
drops under 4.75 V.
Transistor Q4 controls the voltage to the compressor at the rear
of the QA-ES. The compressor is connected to J5. The micro-
processor issues a digital signal at PWMA, depending on the
ventilation speed desired. Transistor Q2 controls the basic pow-
er in Q4. When Q4 is turned off (low ventilation speed), the
compressor receives power via transistors R8 and R17, leading
to a voltage drop.
2. Microprocessor System
1
To Next Page
Loading...
Need help?
General
