G.R.A.S. RA0075 User manual

Instruction Manual
RA0075 6cc Coupler ANSI 3.7 and IEC 60318-3
www.gras.dk
LI0078 – 28 September 2017

Revision History
Revision Date Description
1 28 September 2017 Extracted from Earbook as separate document
Any feedback or questions about this document are welcome at [e-mail].
Copyright Notice
© 2005-17 G.R.A.S. Sound & Vibration A/S
http://www.gras.dk
Any technical documentation that is made available by G.R.A.S. is the copyrighted work of
G.R.A.S. and is owned by G.R.A.S.
The content in this document is subject to change without notice. G.R.A.S. Sound & Vibration A/S
is not liable or responsible for any errors or inaccuracies that may appear in this document.
Trademarks
Any other product names mentioned in this document may be trademarks or registered trade-
marks of their respective companies and are hereby acknowledged.
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Contents
Introduction.................................................................................. 4
Components.............................................................................................. 4
Characteristics ........................................................................................... 5
Exploded View........................................................................................... 6
Warranty, Service and Repair ........................................................... 7
Calibration................................................................................................. 7
Warranty................................................................................................... 7
Service and Repairs.................................................................................... 7
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Introduction
The G.R.A.S. RA0075 is a coupler for testing earphones. It uses a 1” microphone.
The RA0075 complies with the requirements of:
ANSI S 3.7 American National Standard for Testing Earphones.
It is also part of the 43AF Artificial Ear.
Components
The RA0075 comprises the following components:
RA0075 NBS 9-A Coupler
GR0572 Stop Collar (to maintain consistent coupler-volume)
The RA0075 is delivered as shown in Fig. 1. It uses a 1” pressure condenser microphone with
preamplifier. An exploded view of its user-serviceable components together with a suitable pre-
amplifier and adapter, and microphone is shown in Fig. 2.
Preamplifiers
It can use either a 1” preamplifier or ½” preamplifier with an adapter. The example in Fig. 2
shows:
26AK G.R.A.S. ½” Preamplifier
RA0073 G.R.A.S. ½” - to 1” Adapter
Microphones
It uses primarily a 1” pressure condenser microphone (of the type WS1P) with the normal protec-
tion grid replaced by a special coupler-adapter ring (shown below). It can also be used with protec-
tion grid.
40EN 1” Pressure Condenser Microphone
 ttedwith
RA0074 Coupler-adapter ring
Fig. 1. NBS 9A Coupler RA0075 as delivered
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Characteristics
Main Purpose
ANSI specifies the NBS 9A Coupler for calibrating the earphones of audiometers. It has been
chosen because of it’s simple construction and because the threshold transfer data of so many
different earphones have already been determined.
Volume
It has a volume of about 5.6 cm
3which approximates the volume enclosed by a supra-aural ear-
phone on a human ear.
Frequency
The output level of an earphone on a real ear measured below 500 Hz is lower because of leak-
age and flesh compliance. From 500 Hz to 1500 Hz, it is about the same for both ear and cou-
pler.
Between 1500Hz and 8000 Hz, the response of the coupler is a fair indication of the earphone’s
performance. However this cannot necessarily be used as a precise indication of the relationship
between coupler and ear because of complex interactions between the earphone and its acoustic
load.
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Exploded View
RA0075
NBS 9A Coupler
RA0073
Adapter
½" to 1"
GR0572
Stop collar
40EN
1" Microphone
40EN in Type L
(W.E. 640-AA)
configuration. Can
also be used with
protection grid.
½" Preamplifier
e.g. 26AK or 26AM
Fig. 2. Exploded view of user-servicable parts with a 1” microphone and a ½” preamplifier
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Warranty, Service and Repair
Calibration
Before leaving the factory, all G.R.A.S. products are calibrated in a controlled laboratory environ-
ment using traceable calibration equipment.
We recommend a yearly recalibration at minimum, depending on the use, measurement environ-
ment, and internal quality control programs.
We recommend calibration prior to each use to ensure the accuracy of your measurements.
Warranty
Damaged diaphragms in microphones can be replaced. The microphone diaphragm, body, and
improved protection grid are made of high-grade stainless steel, which makes the microphone
resistant to physical damage, as well as corrosion caused by aggressive air or gasses. This,
combined with the reinforced gold-plated microphone terminal which guarantees a highly reli-
able connection,enables G.R.A.S. to offer 5 years warranty against defective materials and
workmanship.
The warranty does not cover products that are damaged due to negligent use, an incorrect power
supply, or an incorrect connection to the equipment.
Service and Repairs
All repairs are made at G.R.A.S. International Support Center located in Denmark. Our Support
Center is equipped with the newest test equipment and staffed with dedicated and highly skilled
engineers. Upon request, we make cost estimates based on fixed repair categories. If a product
covered by warranty is sent for service, it is repaired free of charge, unless the damage is the
result of negligent use or other violations of the warranty. All repairs are delivered with a service
report, as well as an updated calibration chart.
WEEE directive:
2002/96/EC
CE marking directive:
93/68/EEC
Manufactured to conform with:
RoHS directive:
2002/95/EC
G.R.A.S. Sound & Vibration continually strives to improve the quality of our products for our
customers; therefore, the specifications and accessories are subject to change.
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