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MicroTymp Service Manual
Thank you for purchasing the Welch Allyn MicroTymp. The
operating and maintenance instructions found in this manual
should be followed to ensure many years of accurate and
reliable service. Please read these instructions thoroughly
before using your new MicroTymp.
C o n t e n t s
Introduction to Tympanometry .................................... 1
Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DisplaySymbols,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..15
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..I 6
PaperReplacementt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..19
Wall Mounting Instructions ................................... .2 1
Recharging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 22
Battery Replacement ....................................... .24
Interpretation of Results. ....................................... .26
Guidelines for Screening ....................................... .32
ChargingTransformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 36
Cleaning and Sterilization ....................................... .37
Repair and Recalibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
How the MicroTymp Works. ..................................... .43
Technical Specifications ....................................... .44
MicroTymp-U.S. Patent Number 4,688,582
Introduction to Tympanometry
Aural acoustic immittance measurements have become an
integral component of audiologic and otologic evaluation. One class
of aural acoustic immittance measurement, tympanometty, has
become routine in the assessment of ear disease. Since the original
report of Terkildsen and Thomsen (1959) tympanometry has been
used widely by physicians and audiologists as a research tool for
studying the effects of ear disease on middle ear function and as a
clinical test for detecting medically significant pathology. Recent
technological advances provide the capability for the MicroTymp, a
low-cost, portable, precision instrument that can be of significant
value for determining the need for medical referral, for diagnosis of
ear disease, and for monitoring the course of medical/surgical
The Welch Allyn MicroTymp is a single-component aural acoustic
admittance meter that records a tympanogram with a 226-Hz
probe tone. In order, to properly use the MicroTymp and to interpret
the results correctly, the user should be familiar with the basic
principles of tympanometry!
Acoustic admittance is the ease with which acoustic energy is
transferred from one system to another*. If the air in the ear canal
is easily set into vibration, the admittance is high. If the air is difficult
to set into vibration the admittance of the system is low. The ease or
difficulty of setting the air in the ear canal into vibration is determined
by the volume of air and the admittance of the middle ear. Tympanometry provides a method of evaluating the physical characteristics
of the middle ear by measuring the admittance of the air trapped in
the ear canal.
‘For more in depth information see:
Margolis, 1981; Margolis and Shanks, 1985; Van Camp et al., 1988.
Ya = v
where Ya is acoustic admittance, v is volume velocity, and p is sound pressure. The unit
of acoustic admittance is the acoustic millimho (mmho).
Tympanometry is the measurement of acoustic admittance as a
function of ear canal air pressure. The resulting graph is a tympanogram. Because ear canal air pressure changes the admittance of
the middle ear, the admittance of the air in the ear canal changes
when the ear is pressurized. Positive or negative pressure, introduced
into the sealed ear canal, decreases the admittance of the air in the
ear canal by stiffening the eardrum. The effect of air pressure on
the acoustic admittance measured in the ear canal is systematically
altered by ear disease. Tympanometry is a sensitive indicator of the
effects of ear disease on the acoustical/mechanical function of the
A normal tympanogram is depicted below. Four features of the
tympanogram can be used to evaluate the ear under test:
@Static admittance (Peak Ya) is a measure of the height of the
tympanometric peak. Given appropriate norms, static admittance
is a useful indicator of middle ear disease.
@Equivalent ear canal volume (+ 200 Vea)* is the admittance
value determined with an ear canal air pressure of + 200 daPa
(dekapascals). An abnormally high equivalent ear canal volume
suggests the presence of a tympanic membrane perforation, or a
patent tympanostomy tube.
QTympanometric peak pressure (TPP) is the position of the
tympanometric peak on the pressure axis. TPP is an imprecise
measure of the middle ear pressure. By itself, TPP is not an
accurate indicator of middle ear disease.
OTympanometric gradient (GR) or tympanometric width is a
measure of the width of the tympanometric peak. Defined as the
pressure interval required for a 50% reduction of peak eardrum
admittance, tympanometric width is a good indicator of the
presence of middle ear effusion.
GR = 070 da%
Parts of the MicroTymp
T i p
Battery Cover - R e f e r e n c e
- C h a r g i n g
1. If the instrument has not been stored at room temperature,
allow 45 minutes for instrument to return to operating
temperature range (1535OC or 59-95OF).
2. To turn instrument ON, momentarily depress START/RUN (&D)
button. The OPEN ( =I ) symbol will flash repeatedly in the
center of the screen. The RUN (=s) symbol will flash at the
top of the screen.
NOTE: The MicroTymp will automatically turn OFF 40 seconds
after the last test or activation of any button.
3. Examine the subject’s ear canal opening. Select a tip of adequate size to seal the entrance of the ear canal. Tips are not
intended to be inserted within the ear canal. Improper tip size
will cause leaks. Secure tip to instrument.
4. Grasp the subject’s pinna. Pull gently up and back to straighten
the ear canal (or straight back for children).
5. While maintaining tension on the pinna, press the tip firmly
against the ear canal opening. The tip should point straight
into the ear canal for adults and slightly anteriorly for
children. Inadequate pressure or misalignment will cause LEAK
( = g ) or BLOCK ( z ) errors which prevent the seal necessary
to complete a test.
6. Upon achieving a seal, an indication on the +200 Vea scale will
appear. Points will then progress from right to left across the
display. If BLOCK ( zl~ ), LEAK ( =+ ) or OPEN ( =I ) symbols
appear, reposition probe to start again. For further explanation,
and in case of other symbols, see Display Symbols (pg. 9) for
7. Test is complete when RUN ( =s) symbol disappears, and
ON/READY ( <I> ) symbol reappears. Typical test takes
approximately 3 seconds.
8. To store data for later review or printing:
1. Makesure unit is ON.
2. Match pattern on button with observed ear.
3. Depress appropriate MEMORY (t 3) button.
4. To insure data entry into memory observe memory
symbol on screen.
CAUTION: Holding the MEMORY button down for more than
3 seconds will cause memory to be erased.
9. To start new test, depress START/RUN (6-D) button.
10. Tips may be removed by hand or by sliding the white tip ejector
toward the tio.
1 I. To print results, use Printer/Charger #71130 (pg. 16).
12. To display right ( F ) or left ( 3 ) memory contents, press
appropriate memory button.
13. To erase right ( F ) or left ( 3 ) memory contents, depress
appropriate memory button continuously for 3 seconds. BLANK
MEMORY (-- ) symbol will appear.
14. The MicroTymp will turn OFF automatically 40 seconds after the
last test or last actuation of any button. Contents of memory are
not lost when the unit turns OFF.
The information below may be used as a guide to interpret display
symbols. Symbol names are used throughout these instructions to
describe the graphic display.
The MicroTymp is on and ready for service.
The test is in progress. When test is complete, this symbol is
replaced by ON/READY (&s>) symbol. Results may now be stored
MEMORY #l (Patent’s Right Ear)
The contents of Memory #l are being displayed on the screen.
MEMORY #2 (Patient’s Left Ear)
The contents of Memory #2 are displayed on the screen.
The admittance measurement (Peak Ya) has exceeded the scale
maximum (1.5 mmho). Points which are over the limit are plotted at
The test cannot progress because the measured admittance is less
than 0.2 mmho. This can be caused by:
probe tip lodged against canal wall
ear canal occlusion
l collapsed ear canal
l extremely small ear
Repositioning probe tip will usually alleviate this condition.
The memory location indicated does not contain any data.
The test cannot proceed because desired pressures within the ear
have not been achieved. This occurs when:
l the tip is not completely sealed in the ear canal.
l the tip becomes dislodged during a test.
l the ear canal volume is abnormally large ( > 2cc but I 23x;
above 2.5~~ the OPEN ( =I ) symbol will appear).
To alleviate this condition:
l reposition the tip.
l use a different tip.
l increase pressure against the ear.
NOTE: If a leak condition occurs after -100 daPa pressure is
reached, the pattern will be displayed with a Save the Data Symbol.
SAVE THE DATA
Desired pressures were not reached. This happens when the tip
becomes dislodged in the ear canal or if there is a very slight leak
throughout the test. Though the test has been interrupted, partial
results are displayed. A line at 1.4 mmho has been plotted after the
leak condition occurred. Provided that an identifiable peak is present,
the test need not be repeated. If no peak can be identified, follow
instructions for LEAK (=i= ) condition.
The test has not begun because the total measured admittance (the
sum of + 200 Vea and Ya) exceeds 3.5 mmho. This occurs when:
the unit is not in an ear.
the probe is not completely sealed in an ear.
used on perforated or hypermobile tympanic membrane, an ear
with patent tympanostomy tubes, or an extremely large canal.
Use of a different tip size may alleviate this condition. See
Guidelines for Screening (pg. 32) if condition persists.
It is necessary to recharge MicroTymp (pg. 22) as battery voltage
has fallen below the level required for testing. The START/RUN
(bb) button is inoperative. The MEMORY (t 9) buttons may be
used and data may be printed.
PRESSURE RANGE ERROR
The air pressure in the ear canal when the test began was not
correct. The MicroTymp sensed this error. To alleviate this condition,
restart MicroTymp. Should this symbol persist, return instrument
for servicing (pg. 39).
NOTE: Gradient values are computed by the Printer/Charger and
will appear at time of printout.
Parts of the MicroTymp Printer/Charger
Paper Feed Button .I
7 Print Button
Power Plug 2
Printer/Charger Operating Instructions
WARNING: NOT FOR USE IN THE PRESENCE OF FLAMMABLE
ANESTHETICS. POSSIBLE EXPLOSION HAZARD.
To print copies of data stored in MicroTymp:
1. Place Printer/Charger on a flat, horizontal surface or mount on a
flat;vertical surface (pg. 21).
2. Connect the power plug to receptacle of proper voltage, frequency
and plug type (pg. 46). The green power indicator will become
3. Place MicroTymp in the well with the tip pointing away from the
cord. When MicroTymp is properly seated, the red charge indicator will become illuminated. Charge indicator may flicker during
r------ Print Button
4. Depress and hold PRINT ( q ) button momentarily. Once the
printer starts, the handle may be removed from the well. The
red indicator may flicker during printing. A two-ear print-out takes
approximately 40 seconds.
CAUTION: Pull paper straight up and to the right toward the
back of the unit; pulling too far from side to side or in a
downward motion will cause paper to jam.
5. Printed results are an exact copy of information on the MicroTymp
display that was stored in memory. If only one memory had data,
then only one result will be printed. For a duplicate copy of results,
depress PRINT ( q ) button again after first printout is complete.
6. Other Messages:
There was either no MicroTymp in the well or it was not seated
properly. Reseat the MicroTymp and ensure that red indicator is
Both memories were empty.
To feed extra paper, press FEED ( b ) button. Paper will continue
to feed as long as the button is depressed.
The QUICK CHECK provides a complete functional test of the
The QUICK CHECK should be used at least once per month and
whenever there is any question regarding MicroTymp operation. This
provides rapid assurance that the MicroTymp is working properly.
To use the QUICK CHECK:
1. Test .5cc QUICK CHECK cavity as if it were an ear, holding unit
carefully to prevent movement. Printer should not be running during
the test, and stand should be located on a flat vibration-free surface.
Excess noise or vibration during test will cause inaccurate
2. Print results for that tracing only (other memory should be empty).
3. Insert results in QUICK CHECK window.
4. Align baseline and +200 Vea axis of the printout with window.
5. The printed value of +200 Vea should fall within the 0.5~~ box
on the window. If the printout is outside the box, return
MicroTymp for recalibration.
6. Repeat steps 1-5 , using the 1.9cc QUICK CHECK cavity and box.
NOTE: While QUlCK CHECK provides a functional test, it does not
As the altitude above sea /eve/ increases, the admittance of an air
filled cavity also increases. Therefore, at elevations above 2,600
feet, results using QUICK CHECK will change as follows:
+ 200 Vea Reading Change
2,600 ft. (792 m)
5,000 ft. (1,525 m)
Pink strip indicates need for immediate paper replacement.
CAUTION: Failure to change paper within 4 printouts after the
pink strip appears could result in damage to print mechanism.
1. Remove paper access door by sliding it to the right.
Paper Access Door
2. Remove and discard old roll of paper, but save black plastic
3. Cut end of new roll squarely and insert black plastic
spindle. Torn edge will prevent paper from feeding properly
and could cause paper jam.
4. Slide this assembly into grooves into Printer/Charger, making sure
to insert paper into feed slot as shown. Push paper while depressing feed button. The paper will be pulled in by the printer.
Continue depressing feed button until paper exits top of stand.
possible loose areas.
5. Slide paper access door to the left until it snaps closed.
CAUTION: Ensure paper is taut before closing paper access
door. Loose paper can cause printer malfunction.
NOTE: Use only Welch Allyn paper (#53600) or Printer/Charger
life will be lessened and warrranty voided.
DISASSEMBLY OF PRINTER/CHARGER PRESENTS POSSIBLE
ELECTRICAL SHOCK HAZARD.
REFER ALL SERVICING TO QUALIFIED PERSONNEL TO
PREVENT POSSIBLE FIRE HAZARD.
Wall Mounting Instructions
1. Choose a location for Printer/Charger within five feet (1.5m) of an
2. Position mounting bracket vertically on wall and use as template
to pencil markings for drill holes.
3. Select correct mounting hardware from two provided:
Sheet metal screws and plastic anchors-for concrete block
or plasterboard, use 0.187 in. (4.75mm) diameter drill. Secure
anchors to wall.
Sheet metal screws only-for metal panel or wood walls, use
0.120 in. (3.05mm) diameter drill.
4. Fasten mounting bracket to wall with screws.
5. Mount unit by aligning Printer/Charger cut-out with top of bracket.
Push down until seated securely on bracket.
The 7.2V nickel-cadmium battery used in the MicroTymp will provide
approximately 60 minutes of continuous operation. When the battery
is low, the LOW BATTERY ( 1+ ) symbol will appear on the
The START/RUN (bb) button is automatically disabled under these
conditions to prevent inaccurate results due to inadequate battery
voltage. Results may be stored, recalled or printed when the battery
is low. The MicroTymp may be recharged by any of these three
1. CHARGING TRANSFORMER
Any of the Welch Allyn’s charging transformers (pg. 36) may be
used. To recharge:
1. Plug the transformer into a receptacle of appropriate
voltage, frequency and plug configuration.
2. Place MicroTvmp on its side and plug the output cord of the
transformer into’ the charging jack. -
(71040 Charging Transformer shown)
2. MODEL 71123 AUDIOSCOPE CHARGING STAND
Follow directions included with stand.
3. MODEL 71130 PRINTER/CHARGER
1. Place Printer/Charger on a flat horizontal surface or mount it
on a flat, vertical surface (pg. 21).
2. Connect the power plug to a receptacle of proper voltage,
frequency and plug type (pg. 46). The green power indicator
will become illuminated.
3. Place MicroTymp into the charging well. MicroTymp will fit
into the well only one way. When properly seated the red
charge indicator will become illuminated.
A fully drained battery may be recharged overnight by any of the
preceding methods (71040 Charging Transformer, 71130 Printer/
Charger or 71123 Charging Stand). The MicroTymp may be charged
indefinitely without damage to the battery.
l Slight heating of MicroTymp handle is normal
l Batteries will not leak
l Batteries will discharge gradually over a period of about 60
days when stored at room temperature (7O’F). Storage at higher
temperatures will accelerate discharge rate.
The MicroTymp battery is intended for many charge/discharge cycles
and is warranted for two years (expiration date is imprinted on
battery). REMOVAL OF BATTERY WILL RESULT IN LOSS OF
MEMORY CONTENTS. To replace:
1. Allow MicroTymp to turn OFF.
2. Unscrew battery cover using a small Phillips head screwdriver.
Save this screw.
3. Remove battery cover by lifting up and away from the tip end of
4. Grasp and pull up on battery.