Welch Allyn PneumoCheck User manual

Service Manual

Operator Manual

Cardio Menu

PneumoCheck™

Spirometer Model # 61000,

Printer Charger #’s 76100 & 76106

Part 610132

Welch Allyn Medical Division

4341 State Street Road

P.O. Box 220

Skaneateles Falls, NY 13153-0220

Copyright 1997

.oNtraP.veRegnahCfonoitpircseD#NCEetaDdevorppA

231016D noitamrofnIgnitoohselbuorTedulcniotnwardeRdnadesiveR 09563-579tcOerbmetteS.R
231016E 2noitceSnitseThcneBregrahC/retnirPdeddA 52324-500.voNorreLnarF

DRAWINGS AND/OR ILLUSTRATIONS AND/OR PART NUMBERS CONTAINED IN THIS DOCUMENT
ARE FOR REFERENCE PURPOSES ONLY! FOR CURRENT REVISIONS CALL WELCH ALLYN.

Service Manual 610132 Rev. E Pneumocheck Handle and Printer/Charger 1

2 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Contents

General Information........................................................................................................... 5

1.1 Handheld Spirometer ................................................................................................................6

1.2 Printer .........................................................................................................................................8

Service ...............................................................................................................................11

2.1 Bench Test Of Pneumocheck.................................................................................................12

2.2 Bench Test of Printer Charger................................................................................................17

2.3 Required Tools and Equipment .............................................................................................21

2.4 Test and Adjustment Procedures ...........................................................................................22

Theory of Operation ..........................................................................................................23

3.1 Spirometer Circuit Description ..............................................................................................24

3.2 Spirometer - Printer Circuit Description ...............................................................................30

3.3 Messages.................................................................................................................................33

Troubleshooting................................................................................................................37

4.1 PneumoCheck Handle Technical Troubleshooting ............................................................. 40

4.2 Customer Service Questions and Answers.........................................................................43

Disassembly and Repair...................................................................................................49

5.1 Pneumocheck Handle Disassembly Procedures ................................................................ 50

5.2 Pneumocheck Printer/Charger Disassembly Procedures ................................................. 56

Pneumocheck Handle and Printer/Charger Spare Parts ...............................................65

List of Drawings and A Specs ..........................................................................................67

Service Manual 610132 Rev. E Pneumocheck Handle and Printer/Charger 3

Help Information:

• All service and repairs must be performed by authorized Welch Allyn personnel or

agents, using Welch Allyn replacement parts. Failure to do so will invalidate the
product warranty.

• If you have any questions about servicing the 61000 Pneumocheck or the 76100 or
76105 Printer Chargers, please call or write Welch Allyn:

Attn: Product Service Department

Welch Allyn, Inc.

4341 State Street Road

Skaneateles Falls, NY 13153-0220

U.S.A.

Telephone: [phone]

Fax: [phone]

• Troubleshooting assistance is contained in Section 4 of this manual.

• Please read and understand the PneumoCheck and Printer/Charger Operating

Instructions PN 610140-3.

4 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 1 - General Information

1.1 Basic Description - Handheld Spirometer

1.2 Basic Description - Printer

General Information

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 5

Section 1 - General Information

1.1 Handheld Spirometer

Refer to Owners Guide

P/N 610140-3

The handheld spirometer is a small, battery operated
device incorporating a laminar flow sensing pneumatic
liquid crystal display, and electronic circuitry in an
injection molded case.

The front panel of the handheld spirometer includes the
eight character, alphanumeric display, two push-button
keys labeled TEST and DATA, an ON/OFF slide switch
and a battery charge indicator light. The flow sensor is
housed in the top portion of the device and is removable
for cleaning and sterilization. The mouth piece is at one
end of the flow sensor and fits disposable cups or
disposable cardboard tubes. There are two electrical
contacts on each side to the spirometers batteries. On
one side of the spirometer is a DC jack for battery
charging in case the operator chooses not to purchase
the optional printer base.

The main function of the handheld spirometer is to
gather data from two kinds of spirometry maneuvers by
patients: the FVC maneuver and the MVV maneuver.

The TEST key is used to select and perform the desired
test. It is normally pressed when the spirometer is
displaying the word SELECT. It can also be pressed
during a maneuver or during the results display to
prematurely quit a test and begin another.

The DATA key is used to continue whenever the device
pauses to display some information. When the word
SELECT is being displayed, the DATA key can be used
to show the results of the test that is currently stored in
memory.

The general flow of usage of the device starts with the
selection of a test. The operator then waits for an
audible beep, indicating that it is ready to acquire data
from the maneuver. The patient puts the mouth piece to
his mouth and performs the maneuver. Upon
completion indicated by another audible beep, there is
a brief delay while the results are calculated then the
result messages are displayed. This completes the
loop, and the machine goes back to SELECT and waits
for another keypress.

6 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

6 Pneumocheck Handle and Printer/Charger

Section 1 - General Information

When not in use, the handheld spirometer sits-in the
cradle of the printer base (or it is connected to an outlet
via a DC power adapter,) and the battery is charged.
The battery indicator light remains on whenever a
source of charge current is present. The spirometer
becomes operational when it is lifted from the printer
base or disconnected from the DC adapter. The
spirometer is functional only while disconnected from
the charger or printer base and the ON/OFF switch is
ON. The word SELECT appears on the display and the
device waits for a keypress from the operator.

When the word SELECT is on the display, you can do
one to the following:

1. Press the test key which will start the sequence
for doing an FVC test, and MVV test, or a
calibration of the spirometer.

2. Press the DATA key which will display the test
values of the best test of a test is currently
stored in the spirometer’s memory.

3. Put the spirometer back into the printer cradle
which will start the sequence for transmitting
any test data in the spirometer’s memory to the
printer’s memory, and then resume charging
the battery.

4. Connect the spirometer to the DC power
adapter, which will resume charging the battery.

5. Turn the unit off using the ON/OFF slide switch.

A more detailed description of the operation of the
spirometer is contained in the Operator’s Manual.

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 7

Section 1 - General Information

1.2 Printer

The printer base consists of a receptacle to hold the
spirometer, a battery charging circuit, a high speed
thermal line printer, and associated microprocessor a
power circuitry, all housed in an injection molded case.

The front panel of the printer includes 2 indicator lights,
and 3 push button keys marked STOP, FEED, and
PRINT. Also on the front panel are 5 numeric rotary
switches: 2 digits for AGE, and 3 digits for HEIGHT.
The are also 2 slide switches for selecting SEX and
RACE.

There is a set of 4 option switches located on the
underside of the unit.

The main function of the printer base is to print reports
of spirometry tests performed by the handheld
spirometer, and to charge the spirometer’s battery.

The general flow of usage is as follows:
When the spirometer is placed in the cradle of the base,

it immediately begins sending data to the printer base
during which time the message SENDING appears on
the panel of the printer base. Once the data transfer is
complete, the printer base gives a compound beep and
continues to charge. The READY light on the printer
base turns on solidly, indicating that there is a test
stored in its memory. The operator then sets the patient
demographic switches for the patient, then presses the
PRINT key to print the report.

There are two indicator lights on the front panel of the
printer base. One is labeled POWER and is on
whenever the unit is plugged into a powered outlet. The
other light is labeled READY, in the memory of the
printer base. When the device is receiving data from
the spirometer, this light flashes. Once the transfer is
complete and test is in memory, the light remains on.

8 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 1 - General Information

The READY light is also used to indicate an error
condition. Errors are numbered from one to three.
When an error occurs, an alarm sounds and the
READY light flashes in groups of 1, 2, or 3 flashes (at a
rate of times per second), corresponding to the error
that was detected. A one second pause occurs between
these flashes. This continues until the error condition
has been cleared.

The PRINT key is used to print a report. If there is no
report to be printed and the PRINT key is pressed, a
short chirp will sound and no report is printed.

The FEED key is used to feed paper out of the printer.
The paper is fed as long as the key is held down. The
key is not operable while a report is being printed or
while the data is being transferred from the spirometer.

The STOP key aborts the current task (report printing or
data transfer) and returns to the wait state of the base.
It is also used to clear the machine of any error
condition that it might be in. It does not clear the printer
base’s memory.

The demographic switches are used to indicate the
patient’s age, height, sex, and race. The AGE switch
consists of two digits, each of which can range from 0 to

9. The range of valid values depends on the normal

being used.

The HEIGHT switches operate in the same manner as
the AGE switch, except that it has three digits. Either
inches or centimeters can be used for the height. As
was the case for AGE the range of valid values depend
on the normal being used.

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 9

Section 1 - General Information

If the value for either age or height fails outside of valid
range, then the normal values are not calculated or
printed on the report.

The SEX switch is a slide switch. The up position
indicates the patient is a female, while the down
position indicates that the patient is male.

The RACE switch is also a slide switch. The up position
indicates race group 1 and the down position indicates
race group 2. Race group 1 is used if the patient is
Black, Oriental, East Indian, or Pakistani. Race group 2
is used for all other races.

There are four option switches located on the underside
of the printer base. The switches are dip switches that
can be in either the ON or OFF position. These switches
can be changed while the printer base is on. The
options specify certain aspects of the report printing.
They are:

1. OFF

2. OFF Knudson, 1983

1. ON

2. OFF Knudson, 1976

1. OFF

2. ON Morris, Crapo et al

1. ON

2. ON European

3. OFF: Short report form

3. ON: Long report form

4. OFF: Flow/Volume plot

4. ON: Volume/Time plot

These options are discussed in further detail in the
Operator’s Manual.

10 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 2 - Service

2.1 Bench Test of Pneumocheck

2,2 Bench Test of Printer/Charger

2.3 Required Tools and Equipment

2.4 Test and Adjustment Procedures

Service

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 11

Section 2 - Service

2.1 BENCH TEST OF
PNEUMOCHECK

SECTION A

1 Remove pneumotach if necessary.

Caution: Adequate ESD protection
must be worn at all times when
working on the Pneumocheck,
handle or printer/charger.

2 Obtain a good set of batteries and insert in

pneumocheck.

3 Replace pneumotach. Turn pneumocheck on. If

unit powers up continue testing (steps 3 &
beyond). If unit doesn’t power up, take apart.
Refer to troubleshooting guide.

4 Put into data mode (hold down white button,

turn unit on and release white button).

5 Observe LCD; all segments should be on.

6 Depress and release ‘test’ button. Unit should

step through a self diagnostic.
Testing > ROM OK > RAM OK > EEPRM OK>
ASLEEP

In ‘ASLEEP’ mode, the unit will stop and await
further instruction.
If unit stops before sleep mode, there is a
failure. Refer to troubleshooting guide.

7 Depress & release test button: ON reading

should be displayed. It should read
between 30 and 80. Continue testing whether
on reading is in range or not.
Calibration of this circuit will be covered in
SEC B, STEP 6.

8 Depress & release test button: Unit should give

BAT reading. This should be 815 +/- 1%
(807-823). Even if number is outside of range,
continue on to steps 9-12. Refer to
troubleshooting guide to diagnose after
completing step 12.

12 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 2 - Service

9 Depress & release test button: Ambient

temperature should be displayed.
20 degrees C = 68 degrees F
22 degrees C = 72 degrees F
24 degrees C = 75 degrees F
25 degrees C = 77 degrees F
27 degrees C = 81 degrees F
30 degrees C = 86 degrees F
If unit displays a reading outside ambient
temperature range, complete steps 10 thru 12.
Then, refer to troubleshooting guide. If unit
displays a reading of 390-400 degrees F,
check battery voltages. If battery voltage is
low, replace battery and repeat steps 4 thru

12.

10 Depress & release test button: Unit should

read FO = 55. This is a software coefficient.

11 Depress & release test button: Unit should

display a flashing ‘BAT OK’ message.

12 Depress & release test button: Unit should

display ‘DO DCV’ message.

13 Turn unit off. Depress test button and turn unit

on, release test button. Unit should read:
‘Test Mode’ >VER.3.5 >clear > select. The
latest software is VER 3.5: If unit reads VER

3.2, the software must be changed. The
PROM is part no 610102-535. It goes into
position U4 of the LCD digital PC board.

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 13

Section 2 - Service

Disassemble Unit:

SECTION B

Wear ESD wrist strap when performing the
following operations.

1 Observe backplate; notice what must be

present:

If there is a raised surface where the ‘flat’
should be and/or if there is no recessed circle,
replace backplate (610015-503).Remove
battery holder before discarding old
backplate.

NOTE:Observe back of LCD board. If back of
LCD board does not have a metal bar, you
must replace this board.

2 Apply a moderate amount of force to the side

of each battery contact. Contact should hold
firm. If it does not, take battery contact off and
clean any dried epoxy off of metal conducting
surface on PC board.
Obtain a new battery contact (610067-1) and
solder to PC board, noting proper
positioning.

Before soldering, screw contact onto PC board
with appropriate hardware.

Lastly, tighten to specifications (approx. 12-16
in/oz.) or until moderately firm. Take note that
black fiber washer is not destroyed. Perform
this step whether epoxy was adequate or
contact had to be soldered.

14 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 2 - Service

3 If required, change Red LED to orange

(230015-6).

4 If necessary, change software. You must

remove digital board from front plate to do
this. PROM is location U4 on digital board.

5 If necessary, reverse side contacts. To do this,

remove the two metal contacts from the black
plastic piece. Reverse the plastic piece so that
metal contacts will be raised outside of plastic
surface of main frame. Do this for each side.

6 Calibrate the transducer circuit: to get to ON

reading, see steps 4-7 section A. If ON
reading was in spec.(see step 7, section A),
set to 50 or as close as you can get (within
5 cts.), using R33 (pot at bottom of PC board).

Apply 58.8 DPA (60 mm of water with
manometer) to transducer via long hose.

Adjust R36 (pot just above R33) to 844 +/- 5
cts. Return to ODPA, reading should be 50 +/­5 cts. Readjust if necessary.

If the transducer reading is outside of the 30-80
range, measure the transducer output ofpins 2 and 4
of the transducer. They are the two white wires
coming from the transducer. You should see no more
than approx. 300 micro volts (.3mv). If this is the
case, readjust ON reading to spec. as per sec. B,
step 6.

If you see more than 300 mcvolts (.3mv), replace
transducer.

If you cannot build pressure in transducer,
diaphragm is torn, replace transducer.

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 15

Section 2 - Service

Once transducer is replaced, calibrate according to
Section B, step 6.

Once transducer is calibrated, re-assemble unit.

7 With unit assembled and good batteries in,

without the pneumotach (top piece), insert
into working printer charger. With a DC
ammeter, measure current between the top
of each battery. You should see approx. 11 ma
recharge current.
If reading is outside of 10-12 ma, refer to
troubleshooting guide.

8 If reading is good, assemble pneumotach onto

handle. Obtain final test form.
Step through, test in ‘DATA’ mode as per
Section A, steps 4-12 .
Observe ‘ON’ reading . As you do this and
write down in appropriate place on form.
Continue to move forward until you see DO
DCV.

At this point throw switch on test printer to RXTX OK
position. This puts a short circuit between the RX and
TX communication lines. Insert handle. The following
messages should appear:

DCV SEEN > RXTX OK > CHARGE > screen blank.
If they do, remove handle, the message DO DCV

should re-appear. Return switch on test printer to RX
fail position.

These tests are taken from spec. A01943 Rev.F.

Get ready to calibrate w/3.0 liter syringe according to
spec. A01945 Rev.D.

16 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 2 - Service

1. ESD protection is required whenever working with the
pneumocheck printer .

2. Apply power to the unit. It should beep twice and the
“power LED” will light. The “data” light should not be
lit.

3. Note and record “dip” switch settings if customer
owned. These switches will have to be returned to
these positions when testing is complete.

4. Check printer well to make sure there is no foam pad.
If there is one, it must be removed. Make sure printer
is powered down. Remove pad by walking and rolling
back pad from ends. Move slowly as to not tear the
pad if possible. Continue until pad is removed. Clean
remaining adhesive with an adhesive remover solution.
Try to avoid scratching the printer well plastic piece.

2.2 Bench Test of the

Pneumocheck Printer/charger

5. Complete the following tests: A .
With a DVM set on the 200VDC range, measure 14vdc
across contacts as shown below that are marked with
an (**).

14 vdc

** ##

gnd

## **

B. Check voltage between ground contact in printer
well and pin 8 of the J2 connector. The J2 connector is
the longer of the two groups of pins in front of the
printhead. Pin 1 is at the left end of the longer group,
counting left to right. The voltage should be between

4.75 and 5.75 vdc.

C. Check voltage between ground contact in printer
well and pin 1 of the J2 connector. The voltage should
be 24vdc +/- .5 volts.

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 17

Section 2 - Service

D. Install a paper roll if one is not installed. Measure the

dc voltage between the ground contact in printer well
and pin 3 of the J1 connector . The J1 connector is the
smaller of the two groups of pins in front of the
printhead. Pin 1 is on the left, counting left to right.
The voltage should be 3.00 vdc or less.

6. Making sure the red capped lever at right of printhead
is pushed all the way toward the back of the printer,
hold down the feed button. The paper should advance
steadily forward.

7. Hold down feed button, then press and release the
stop button. The paper should automatically feed in
the reverse direction. Release the feed button. Paper
will stop feeding.

8. Push the print button. The unit should beep,
indicating that it has no data. The data light should
remain unlit.

9. Download data into printer by placing spirometer
handle, in on state, with data in it, into the printer well.
The data light should flash repeatedly for several
seconds. After this, the data light should be lit.

10.Make sure all dip switches on bottom of printer are
set to the “off” position. On top of printer, set the
following: Age: 36; Height: 159; Race: 2; Sex: F .

Depress and release the print button to obtain a
printout. The printout should agree with the settings.
Also, the standard printed should be Knudson 1976
(dip switches 1 and 2 in off position), short form (dip
switch 3 in off position), and the flow over volume graph
(dip switch 4 in off position).

18 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 2 - Service

1 1.Set dip switches on bottom of printer to “on” position.

On top of printer, set the following: Age: 59; Height:
96; Race: 1; Sex: M.

Depress and release the print button to obtain a
printout. Observe printout. The printout should agree
with the settings. Also, the standard should be Euro
CCS (dip switches 1 and 2 in on position), the long
form, which is a questionnaire (dip switch 3 in on
position), and the volume over time graph (dip switch
4 in on position).

12.Return dip switches to position they were when unit
came in from customer. If unit is a loaner , or a new unit
being returned to stock, set all dip switches to off
position.

13.Hold down the print button and press/release the stop
button. Release the print button. A test printout should
print. At right side of top line, check the version of
software. It should be V3.2. If it is V3.1, it needs to be
changed. The “PROM” that controls this is in position
U5 on the main

pcboard. Replace existing Prom with

part number 610102-506. This Prom is software
version V3.2.

14.Perform agency tests on printer. These include the
ground continuity test and the leakage current test. If
the main pcboard, transformer or line filter was
replaced, perform the hypot test. Observe standards.
They are:

Ground continuity test: .2 ohm maximum
resistance with 10 amperes of current flow through the
earth ground line from the wall plug to a distant metal
point on the unit, probably the transformer screw
opposite where the ground wire is connected;

Leakage current test: 100 microamps or less
from any dead metal part on printer to earth ground,
with the printer ungrounded and powered up.

Hypot test: 1200 vac across the hot and neutral
(tied together) and earth ground for one second without
breakdown (voltage reduction).

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 19

Section 2 - Service

15.This concludes the printer bench test. Make sure there
is an ample supply of paper in printer. When loading
paper, feed about 2-3 inches, put leading edge of
paper through paper cutter envelope before putting
paper cutter in place. Any questions call Welch Allyn
Technical Service at 800-535-6663, Technical
Support.

20 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 2 - Service

Required Tools:

1. Compression ring tool - Welch Allyn tool
number T8608

2. Snap ring pliers (external) VACO #22

3. #1 Phillips head screwdriver

4. 1/4 inch flat head screwdriver

5. 3/32" Hex Key

Required Test Equipment

1. Merriam M131 Manometer with C34259
mount kit or Welch Allyn Pressure
Applicator Box.

2.3 Tools and Test
Equipment Listing

2. Pressure Source - Welch Allyn number

T9161

3. 0-7VDC Power supply with 100 mA current
limit

4. 0-14VDC Power Supply

5. 0-50mADC ammeter

6. 0-14VDC voltmeter

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 21

Section 2 - Service

2.4 TEST AND

ADJUSTMENTS

PNEUMOCHECK HANDLE

A set of specification drawings have been included in
Section 7 with reference made to them here. The
following tests should be done before the unit is
returned to the customer.

1 Calibrate and test the handle per specification

drawing A01945. “Calibrating with Welch Allyn
Spirometer.

2. Perform all tests on specification drawing
A01951, “Dynamic Waveform Testing”

For troubleshooting use, specification drawing
A01943 has been included for testing at the
PC Board Level.

PNEUMOCHECK PRINTER/

CHARGER

22 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

1. Perform Dielectric Strength Test per:

A00167- UL/CSA Models
A00178- IEC Models

2. Perform Leakage Current Test per A00171

3. Perform Grounding Continuity Test per:

A00172 - UL/CSA
A02242 - IEC

4. Perform all tests listed on A01958, “Base Final
Testing”

For troubleshooting use, specification drawing
A01946 has been included for testing at the PC
Board Level.

Section 3 - Theory of Operation

3.1 Spirometer Circuit Description

3.2 Spirometer - Printer Circuit Description

3.3 Messages

Theory of Operation

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 23

Section 3 - Theory of Operation

3.1 Spirometer Circuit Description

General

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.

24 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E

Section 3 - Theory of Operation

In this state:

i. VA+ and VA- are not present
ii. U12 and U13 are not powered
iii. U8 i s not operating
iv . CR1 is oscillating (8Mhz)
v . The CPU clock (pin 22 of U4) is running

(2Mhz)

In normal operation this state will terminate and
return to the sleep state as soon as the p ro ce ss or
has nothing to do, such as while it is waiting for a
keypress.

d. FULL ON In this state all of the circuitry is turned

on. The charge pump may or may not

be operating.

If everything is correct the power consumption in the
four states should be:

State 1: OFF: Less that 0.1ma, typ 0.001ma
State 2: ASLEEP: Less than 2.5ma, typ 1.6 ma
State 3: AWAKE: Less than 16ma, typ 10ma
State 4: FULL ON: Less than 35ma, typ 25ma

NOTE: That achieving these levels is both a hardware
and a software function. Malfunctioning software can

raise the power to as much as 5ma in State 2 and 70ma

in State 4.

The maintenance mode of the spirometer allows it to be

placed in each state for testing purposes.

2. Power Consumption

Service Manual 610132 Rev. E Pneumocheck Handle Printer/Charger 25

Section 3 - Theory of Operation

3. Spirometer Power
Circuit Description

The battery charge is supplied by U14 which is a voltage
regulator wired as a 12ma current source. D6 and D7
provide reverse polarity protection.

Transistor T1 is the source for the current used in the
spirometer if it is turned on while plugged into the
printer. Its output voltage is regulated by the zener D13
to a voltage which will reverse bias D18 while at the
same time insuring that the voltage reaching U8 does
not exceed its design limit of 10v. This means that the
tested voltage at TP1 must lie between 7.7 and 9.6v
with 14-20v applied to the DC jack.

R22 and R23 divide the zener voltage to provide the
sense voltage so that the processor can tell when DC is
applied. This voltage should be between 4.20 and 4.85
volts with DC applied to the charging jack. This sense
voltage is taken to pin 35 of the CPU and pin 1 of the U1.

The raw power for the spirometer comes from either the
battery via D18, or if DC is supplied, via T1. It goes
through the ON/OFF switch SW1 to the 5v regulator

119. U9 also supplies the low battery warning if Vcc
comes out of regulation. This will occur when the
battery voltage drops below about 6.3 volts.

Power for the analog sampling circuitry is taken directly
from the battery so that it is impossible to test patients
while powering the unit from the DC jack. T5 and T6
form a software controlled switch to turn analog power
on only while actually needed and thus conserve
battery power. This voltage will be on when CPU pin 2
is high. The voltage at the collector of T6 will be 6 to 10
volts when on, and can be easily tested at pin 1 or U1.

This switched analog voltage is inverted by U8, which
should have a visible charge pump oscillating at eight
kilohertz across C18. It will develop at least -6 volts
across C20.

The switched analog voltage and its inversion are
regulated by U7, T3, and T4 to provide +/- 4 volts VA+
and VA-. R18 and R19 divide Vcc to provide a guide
voltage. U7A and T3 use this voltage to give VA+. U7B
and T4 invert VA+ to provide a matching VA-.

26 Pneumocheck Handle and Printer/Charger Service Manual 610132 Rev. E