Service Manual
AT235
III
6.1 Calibration properties
Calibrated transducers:
Contralateral earphone: Telephonics TDH39/DD45 with a static force of 4.5 N 0.5
N and/or EARtone 3A and/or CIR insert phone
Probe system:
Ipsilateral Earphone: is integrated in the probe system
Probe frequency transmitter and receiver and pressure
transducer is integrated in the probe system
Accuracy:
General:
Generally the instrument is made and calibrated to be
within and better than the tolerances required in the
specified standards:
Reflex Frequencies:
±1%
Contralateral reflex and
audiometer tone levels:
3 dB for 250 to 4000 Hz and 5 dB for 6000 to 8000 Hz
Ipsilateral reflex tone
levels:
5 dB for 500 to 2000 Hz and +5/-10 dB for 3000 to 4000
Hz
Pressure measurement:
Compliance
measurement:
5% or 10 daPa, whichever is greater
5% or 0.1 ml, whichever is greater
Stimulus presentation
control:
Reflexes:
ON-
OFF ratio ≥ 70 dB
Rise time = 20 ms
Fall time = 20 ms
A weighted SPL in Off = 31 dB
Impedance calibration properties
Probe tone:
Frequencies:
226 Hz 1%, 678 Hz 1%, 800 Hz 1%, 1000 Hz 1%
Level:
85 dB SPL 1.5 dB measured in an IEC 60318-5
acoustic coupler. The level is constant for all volumes in
the measurement range.
Distortion:
Max 1% THD
Compliance:
Range:
0.1 to 8.0 ml
Temperature
dependence:
-0.003 ml/C
Pressure dependence:
-0.00020 ml/daPa
Reflex sensitivity:
Reflex artifact level:
0.001 ml is the lowest detectable volume change
≥95 dB SPL (measured in the 711 coupler, 0.2 ml, 0.5 ml,
2.0 ml & 5.0 ml hard walled cavities)
Temporal reflex
characteristics:
(IEC60645-5 clause
5.1.6)
Initial latency = 35 ms (5 ms)
Rise time = 42 ms (5 ms)
Terminal latency = 23 ms (5 ms)
Fall time = 44 ms (5 ms)
Overshoot = max. 1%
Undershoot = max. 1%
Pressure:
Range:
Values between -600 to +400 daPa can be selected in the
setup.
Safety limits:
-750 daPa and +550 daPa, 50 daPa
Barometric pressure:
The barometer pressure
chances influence on the
impedance measurement
in the specified range
(97300 – 105300
Pascal).
Admittance can vary inside: ± 4%
The pressure accuracy is: ±10 daPa or 10%, whichever is
greater
Height above sea level:
The pressure sensor used, is a differential/gauge type, which means, it measure the
pressure difference and therefore not affected of the height above sea level.
Probe tones 0 meters
500 meters 1000 meters 2000 meters 4000 meters
226 Hz
1.0 mmho
1.06 mmho 1.13 mmho
1.28 mmho
1.65 mmho
678 Hz
3.0 mmho
3.19 mmho 3.40 mmho
3.85 mmho
4.95 mmho
800 Hz
3.54 mmho 3.77 mmho 4.01 mmho
4.55 mmho
5.84 mmho
1000 Hz
4.42 mmho 4.71 mmho 5.01 mmho
5.68 mmho
7.30 mmho
