Welch Allyn Micro Tymp 1, Service Manual

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Section 1.3 General Information
Introduction
The Welch Allyn Micro Tymp Tympanometric System enables the practitioner to per-
form an objective test of the middle ear function. It provides fast and painless measure-
ment on prevalent disease. Results appear instantly on the liquid crystal display and can
be stored and printed in the Printer/Charger.
Basic System Description
There are two major components to the Micro Tymp Tympanometric System: the hand
held Micro Tymp handle, and the Printer/Charger. The handle utilizes a probe with
three portholes: one which leads to a pump and pressure transducer for air pressure, one
for delivering sound from a speaker, and one which leads to a microphone for picking up
the sound. These are clearly shown in Figure 1-1 block diagram.
*
A 226 Hz probe tone is introduced in the sealed ear canal by a miniature loudspeaker.
* A microphone records and monitors the sound pressure produced in the ear canal.
* The sound level is maintained at a constant 85 dB SPL (
SOUND PRESSURE LEVEL
)
throughout a test. Therefore, when the amount of sound absorbed by the middle ear
increases, the speaker must be driven harder to maintain the correct SPL.
* Pressure in the ear canal is changed with a miniature pump. The pressure transducer
monitors this pressure and sends this information to the microprocessor so that it can
control the pump.
* The voltage to the speaker determines its output. Therefore, acoustic admittance is
proportional to speaker voltage.
* As pressure in the ear canal is changed throughout a test, the microprocessor com-
putes acoustic admittance and plots it out.
The Printer Charger stand contains the print head, power supply PCB, fuses, switch
assembly, and microcomputer.
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