GRAS 90CA User manual

Instruction Manual
90CA Microphone Calibration System
LI0056 – 13 May 2019

2
Revision History
Any feedback or questions about this document are welcome at [email protected].
Revision Date Description
1 15 October 2009 First publication of this document
2 01 March 2012 Redesign of the manual. Added information about
calibration in general, calibration of microphone sets,
and preamplifiers. New diagrams and drawings about
hardware assembly and electrical connections
3 10 February 2017 File locations on page 64 corrected, new microphone
definition file.
4 13 May 2019 Adapter Cable with Optical Isolation added.
Warning about uninstalling LabView.
Copyright Notice
© 2012-19 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 product names mentioned in this document may be trademarks or registered trademarks of
their respective companies and are hereby acknowledged.

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Contents
Introduction.................................................................................. 5
Using This Manual ..................................................................................... 5
Introduction to Calibration............................................................... 6
What is Acoustic Calibration? ...................................................................... 6
Which type of calibration do I need? ............................................................ 7
How often should I calibrate? ...................................................................... 8
The Concept of the 90CA Microphone Calibration System ..................... 9
Applications ............................................................................................ 10
The Basic Principles of 90CA: Microphone Calibration in Four Easy Steps ....... 11
Functional Block Diagram ......................................................................... 12
Hardware and Software for Level Calibration ............................................... 13
Hardware and Software for Frequency Calibration ........................................ 14
Delivered Components.................................................................. 16
Assembling and Connecting the Hardware ........................................ 17
Workspace for the Assembly...................................................................... 17
PXI: Connections for Test of Microphones (Ext. Pol. and Prepol.).................... 19
PXI: Connections for Test of Externally Polarized Microphone Sets ................. 21
PXI: Connections for Test of Prepolarized Microphone Sets ........................... 23
PCI: Connections for Test of Microphones (Ext. Pol. and Prepol.).................... 25
PCI: Connections for Test of Externally Polarized Microphone Sets ................. 27
PCI: Connections for Test of Prepolarized Microphone Sets ........................... 29
Assembling the 90CA .............................................................................. 30
Settings for the Instruments included in the System..................................... 32
Precautions for certain Types of Microphones .............................................. 32
Powering on the 90CA ............................................................................. 32
Mounting the Microphones........................................................................ 33
System Verification...................................................................... 37
Initial verification of the system setup......................................................... 37
Day-to-day Verification ............................................................................. 37
Introducing the Calibration Software SW0002.................................. 38

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Calibrating Microphones and Microphone Sets................................... 39
Starting the System ................................................................................. 39
Step 1: Registering the Microphone ........................................................... 41
Step 2: Performing a Level Calibration........................................................ 42
Step 3: Performing a Frequency Response Calibration.................................. 45
Step 4: Storing Calibration Results ............................................................ 46
Calibrating a Preamplifier ............................................................. 47
Step 1: Registering Test Conditions............................................................ 48
Step 2: Frequency Response ..................................................................... 51
Step 3: LEMO Reference Level Test........................................................... 52
Step 4: Storing Calibration Results............................................................. 53
High Frequency Calibration............................................................ 54
Working with the System Files and Documentation ............................ 56
Viewing and Editing the Microphone and Preamplifier Definition Files ............ 56
Setup.txt: The Microphone Calibration System Setup File ............................. 59
Editing the Calibration Charts in DIAdem .................................................... 62
The File Structure on the System Controller ................................................ 64
Warranty and Maintenance............................................................ 66
Warranty................................................................................................. 66
Calibration............................................................................................... 66
Cleaning ................................................................................................. 66
Service and Repairs.................................................................................. 67

5
Introduction
The G.R.A.S. 90CA Microphone Calibration System provides you with a computer-
controlled level and frequency-response calibration of measurement microphones and
microphone sets. This highly automated process is convenient, yet reliable, with its
ready-to-use software and hardware, and auto-generated customizable documentation.
Additional software can be purchased for the calibration of preamplifiers.
Calibration with the 90CA is in compliance with
• ANSI S1.10 – 1966 (R1976)
• IEC Norm 61094-1
• IEC 61094-6
The 90CA provides accurate calibration hardware, easily changeable test conditions and
a highly reproducible calibration method
Using This Manual
Inside this manual, you will find
A description of the principles of the 90CA calibration system, with an overview of the
hardware and software for the different types of calibration in “” on page 8.
Diagrams and instructions for assembling and connecting the hardware for both the
PXI and the PCI version of 90CA “Assembling and Connecting the Hardware” on page
17.
Illustrations of which components of the 90CA to use for the different types of calibra-
tion for the different sizes of microphones: ”Mounting the Microphones” on page 33.
A description of the special calibration software included with 90CA and where and how
you can customize it: ”Introducing the Calibration Software SW0002” on page 38.
Detailed calibration procedures for “In general, the indicators are green when the
measurement is within the preset limits and red when the the measurement is outside
the limits.” on page 39, and for G.R.A.S. preamplifiers in ”Calibrating a Preamplifier”
on page 47 (if you purchased the preamplifier calibration option), and for ”High
Frequency Calibration” on page 54.
Descriptions of the data files included with 90CA and how to modify them in “Working
with the System Files and Documentation” on page 56.
Additional information about the warranty, cleaning instructions, and service and repairs
are also provided on page 66.