6. Component Functions and Parts
This chapter provides a detailed description of the functions of the
main components of the QA-90, as well as a parts list for cross-
reference.
The QA-90 comprises three printed circuit boards: a metering board,
processor and keypad board. There is are two sets of schematic dia-
grams in Appendix B for the measuring system (comprising eight
schematic diagrams) and a set for the processor/keypad system (com-
prising six pages).
The circuit boards are supplied from a 40 W "medical grade" power
source, which delivers +12 Volt and +5 Volt. In addition, a tempera-
ture-protected transformer is connected to the mains to supply a test
current of up to 30A for "protective earth" measurements.
6.1 Theory of Operation
The QA-90 is an electrical safety analyzer based on a 68HCll Motoro-
la microprocessor and a measuring system that is galvanicly isolated
from the processor. The unit is controlled from the front panel and it
is possible to select either manual mode for measuring voltage, cur-
rent and resistance, or an automatic test cycle that provides full safety
testing in accordance with specified standards.
The following standards may be compiled either fully or in part:
IEC 601.1, UL 2601.1, IEC 601.1.1, UL 2601.1.1, IEC 601.2.4, IEC
1010-1, EN 60601-1, VDE 0750 Tl/12-91, BS 5724, CAN/CSA-
C22.2 No 601.1-M90, AS 3200.1, NZS 6150:1990, VDE 0751
T1/12-90, ÖVE 0751, UL 544, HEI 95, HEI 158 among others.
The measurement results, which are shown in the unit's LCD display,
may be stored in the unit's internal memory, or printed out on an ex-
ternal printer. A serial port (RS-232c) enables the unit to be con-
trolled from a PC, simply by using the PRO-Soft QA-90 soft, rare
program.
The unit has a separate input for a bar code pen, which may be used to
record instrument code and class, module code, and number of patient
leads and classes.
The instrument is controlled from an alphanumeric keypad, contain-
ing nine blue "soft-keys," and seven function keys located around the
LCD display. These are used to select the functions shown in the dis-
play. In addition, there is a separate key for selecting patient leads, a
CLR a return key and a confirmation <ENTER> key.
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