Welch Allyn PneumoCheck 61000, Service Manual

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24 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E
The handheld spirometer’s electronics are contained on
two boards, designated the “Digital Board” and the
“Analog Board”. The analog board contains the power
control circuitry, as well as the analog signal amplifiers.
The digital board contains the digital circuitry, as well as
the front panel components.
The spirometer is designed to minimize power
consumption by having four separate operational
states:
a. OFF When SW1 is off only the battery charge
circuit is enabled. Only diode leakage
current flows.
b. ASLEEP In this state SW1 is on and Vcc is
present but the processor is not running. The
switched analog power is off.
In this state:
i. CR1 is not oscillating
ii. RB is oscillating (100Khz)
iii. All port bits are tri-state except for P6
which has all bits low
iv. The data and address bus is passive
v. The RAM is disabled (U5 pin 26 is low)
vi. TP6 is low
Normally in this state, since the LCD controller is
running, there will be something on the display. The
software can, however, intentionally blank the display.
c. AWAKE In this state the digital circuitry is
operating, but the analog power is off. This
state is entered when the processor has some
work to do.
3.1 Spirometer Circuit
Description
General
Section 3 - Theory of Operation