G.R.A.S. 67AX Instruction Manual

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LI0055 – Revision 25 June 2012

Instruction Manual

67AX ½” CCP Ground Array Microphone System

LI0055 – Revision 25 June 2012

Revision History

Any feedback or questions about this document are welcome at gras@gras.dk.

Revision Date Description

1 27 May 2011 First publication 2 25 June 2012 Added calibration and verification information.

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

KEMAR is the trademark of G.R.A.S. Sound & Vibration A/S.

Any other product names mentioned in this document may be trademarks or registered trademarks of their respective companies and are hereby acknowledged.

LI0055 – Revision 25 June 2012

Contents

Introduction .................................................................................. 4

The Package.............................................................................................. 4

Assembling the 67AX System ..................................................................... 4

Calibration and Verification ............................................................. 6

Calibrating the microphone .......................................................................... 6

Verifying the microphone ............................................................................ 6

Technical Specifications .................................................................. 7

Dimensions and Data for 67AX ................................................................... 7

Ordering Information ...................................................................... 8

Accessories ............................................................................................... 8

Calibration ................................................................................................. 8

Warranty ................................................................................................... 8

Service and Repairs .................................................................................... 9

LI0055 – Revision 25 June 2012

Introduction

This manual describes how to assemble, calibrate, and verify the 67AX ground array sets.

The Package

The parts for your 67AX are delivered unassembled.

The following table lists the items included with the 67AX package.

Item Part Number

½” CCP flush-mounted microphone, with 4cm cable and Microdot-toMicrodot adapter AE1038

47AX-S1

O-ring, Ø13.5mm OR0137

O-ring, Ø55mm OR1512

Cover plate, with 8 screws (SK2015 M2.00× 4.00) GR1426

Cable safety clip, with 2 screws (SK2008 M3.00× 8.00) GR1427

Mounting plate GR1425

Windscreen for 67AX AM0375

3m Angled Microdot-to-BNC cable AA0069

Manual LI0055

Assembling the 67AX System

The first step to assembling the 67AX system is connecting the microphone to the cable as shown in Fig. 1.

To assemble the 67AX system:

1. Place the small O-ring in the ridge in the center hole.

2. Place the assembled microphone, grid-side down, in the center hole on top of the small O-ring. Arrange the cable attached to the microphone in the cavity

Fig. 1. An illustration of how to connect the Microdot-to-Microdot adapter on the microphone to the angled Microdot adapter on the 3m cable.

LI0055 – Revision 25 June 2012

surrounding the mounted microphone and fit the cable in the ridge that leads to the outer edge of the plate.

3. Place the large O-ring in the ridge near the edge of the cavity. The large O-ring must lie on top of the cable.

4. Fit the cover plate on top of the microphone and O-ring assembly and fasten in place with 8 screws.

5. Fasten the safety clip over the cable with 2 screws.

These steps are shown in Fig. 2.

(× 8)

Fig. 2. A view of the order for assembling the parts of the 67AX.

LI0055 – Revision 25 June 2012

Calibration and Verification

Note: For complete calibration information, see the pistonphone instruction manual. The instructions here explain the specific details related to the 67AX.

G.R.A.S. recommends calibration prior to each use to ensure the accuracy of your measurements. Verification is performed in situations where you need to check that the microphone is functioning in its setup and cannot check it properly in the laboratory.

Important: The pistonphone calibration adapter and the pistonphone field-verification adapter are designed for use with a 250Hz pistonphone, such as the G.R.A.S. 42AP Pistonphone. Do not use them with any other calibrator or verification device. The 250Hz pistonphone can be used for both calibration and daily verifications.

Calibrating the microphone

To calibrate the microphone in the 67AX, remove it from the mounting plate.

1. Set the pistonphone in an upright position, preferably using a calibration stand for stability.

2. Mount the pistonphone calibration adapter (RA0221) on the pistonphone.

3. Insert the microphone into the adapter on the pistonphone. Press gently to ensure that the microphone is inserted as far as it can go.

4. Turn on the pistonphone and calibrate as described in the instruction manual for the pistonphone.

Verifying the microphone

1. Mount the field-verification adapter (RA0216) onto the pistonphone.

2. Hold the pistonphone steady while centering the opening in the adapter over the microphone.

3. Gently press the pistonphone with adapter over the microphone, ensuring that the microphone is as far in the pistonphone as it will go.

Note: Due to the setup conditions for the microphone, you may not be able to hold the pistonphone steady. As a result, measurements may not be ideal and cannot be used for calibration purposes. These measurements can only be used for verifying that the measurement chain and the microphone especially is functioning as expected.

Important: When performing verification in the field on a microphone with the grid removed, be extremely cautious during measurements. The membrane is vulnerable without the grid and can be easily damaged.

LI0055 – Revision 25 June 2012

Technical Specifications

Dimensions and Data for 67AX

Dimensions

Microphone Ø13.2mm Housing Ø18.0mm

Microphone set height

Without grid 8mm With 9.20mm Weight 15g

Mounting Plate Ø400mm

Data was collected in a temperature of 23°C (±3°C) and in a relative humidity of 60% ±20%.

Frequency response for the set

±2.0dB 3.15Hz – 20kHz ±1.0dB 5Hz – 12.5kHz

Nominal sensitivity for the set

at 250Hz 12.5mV/Pa

Polarization voltage 0V Dynamic range for the set

Upper limit (3% distortion) 146dB re. 20μPa Thermal noise 22dB(A) re. 20 μPa

Temperature

Operation –30°C to +70°C Storage –40°C to +85°C

Static-pressure coefficient

250Hz/25°C -0.008dB / kPa

Humidity (non-condensing)

Range 0 – 100% RH Influence (250Hz) <0.1dB (0 – 100% RH) Influence of axial vibration equivalent to 1m/s² 66dB re. 20μPa Venting Rear-vented

LI0055 – Revision 25 June 2012

Ordering Information

Included Items Part Number

½" Ground array microphone kit (includes 47AX-S1 ½” Flush-mounted microphone set, Ø400mm mounting plate with assembly parts and cable, and windscreen)

67AX

Manual LI0055

Accessories

The following accessories are needed for the 67AX, but they are not included in the basic package. They must be ordered separately.

Accessory Part Number

Pistonphone field-verification adapter RA0216

Pistonphone calibration adapter RA0221

Calibration

Before leaving the factory, all G.R.A.S. products are calibrated in a controlled laboratory environment using traceable calibration equipment.

An individual test certificate is included with each product. The calibration information is also stored in the built-in TEDS.

We recommend a yearly recalibration at minimum, depending on the use, measurement environment, and internal quality control programs.

We recommend calibration prior to each use to ensure the accuracy of your measurements.

Warranty

All G.R.A.S. products are made of high-quality materials that will ensure life-long stability and robustness. The 67AX is delivered with a 5-year warranty.

LI0055 – Revision 25 June 2012

Damaged diaphragms in microphones can be replaced.

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.

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.

G.R.A.S. 67AX Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual