Cirrus MK427 User manual

MK:427 Environmental Noise Microphone
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MK:427 Environmental
Noise Microphone
Revision 9
This manual, the software to which it relates, the
program code and drawings are all:
© Copyright Cirrus Research plc 2016

MK:427 Environmental Noise Microphone
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The content of this manual, any illustrations, technical information and descriptions within this document were correct at the time of
going to print. Cirrus Research plc reserves the right to make any changes necessary, without notice, in line with the policy of
continuing product development and improvement.
No part of this publication may be duplicated, reprinted, stored in a data processing system or transmitted by electronic, mechanical,
photographic or other means, or recorded, translated, edited, abridged or expanded without the prior written consent of Cirrus
Research plc.
No liability is accepted for any inaccuracies or omissions in this manual, although due care has been taken to ensure that is it
complete and accurate as possible.
Accessories supplied by Cirrus Research plc have been designed for use with the instrumentation manufactured by Cirrus Research
plc. No responsibility is accepted for damage caused by the use of any other parts or accessories.
In order to take account of a policy of continual development, Cirrus Research plc reserves the right to change any of the information
contained in this publication without prior notice.
Produced by Cirrus Research plc, Acoustic House, Bridlington Road, Hunmanby, North Yorkshire, YO14 0PH, United Kingdom.
© Copyright Cirrus Research plc 2016
Reference Number 10/16/MK427/09
Document Printing Date Friday, 14 October 2016

MK:427 Environmental Noise Microphone
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Important information ...................................................................................................................................................4
First Steps.......................................................................................................................................................................4
Stage 1............................................................................................................................................................................... 4
Stage 2............................................................................................................................................................................... 4
Stage 3............................................................................................................................................................................... 4
Overview ........................................................................................................................................................................5
MK:427 Microphone Unit System Diagram.....................................................................................................................7
Mounting Information....................................................................................................................................................... 8
General Guidance ...........................................................................................................................................................9
Positioning your MK:427 Noise Sensor ............................................................................................................................. 9
Operation .....................................................................................................................................................................10
External Connections....................................................................................................................................................... 10
Power Supply .................................................................................................................................................................................. 10
Isolated Loop circuit........................................................................................................................................................................ 10
Actuator control.............................................................................................................................................................................. 10
Verification & calibration of the MK:427 ......................................................................................................................12
Routine verification using the electrostatic actuator system ......................................................................................... 12
Explanatory Note –The principle of electrostatic actuation .......................................................................................................... 12
Typical time history trace during using the electrostatic actuation process................................................................................... 13
Reference Calibration...................................................................................................................................................... 14
Specifications ...............................................................................................................................................................17
Optional Extras ................................................................................................................................................................ 17
Appendix 1 Internal wiring connections .......................................................................................................................18
Cable Connections........................................................................................................................................................... 18
Appendix 2 DC Voltage output option ..........................................................................................................................19
Appendix 3 The influence of the background noise level on calibration and verification ..............................................20
Appendix 2 CE Declaration of Conformity.....................................................................................................................21
Equipment Description .................................................................................................................................................21
Warranty Information. .................................................................................................................................................22
Cirrus Research Offices .................................................................................................................................................23

MK:427 Environmental Noise Microphone
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Important information
Each MK:427 unit will have its own output levels and electrostatic actuator output levels. Please
refer to the factory calibration setup information for details for your specific instrument.
The MK:427 is supplied with the configuration preset to meet those ordered from the factory.
Calpot R1 is referred to in the Reference Calibration section on page 14. This is the only setting that
should be altered, if required, by the user during a Reference Calibration.
First Steps
Once you have received shipment of your new MK:427 Noise Sensor unit, we would recommend the
following stages to setup and install the equipment.
Stage 1
Understand the contents supplied with the MK:427.
See page 7, MK:427 Microphone Unit System Diagram
Stage 2
Integrate the unit with your own systems in 'test conditions' to ensure the unit is correctly
communicating information and measuring and calibrating effectively.
See Factory Configuration Information Sheet
Page 5, Overview
Page 12, Verification & calibration of the MK:427
Stage 3
Install the MK:427 in a suitable site.
See Page 8, Mounting Information
See Page 9, Positioning your MK:427 Noise Sensor

MK:427 Environmental Noise Microphone
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Overview
Thank you for choosing the MK:427 outdoor noise sensor. This high quality outdoor environmental
noise microphone system is ideal for integrating with other data logging and external measurement
systems.
The mechanical and acoustic design of the MK:427 has been field proven over many years in a range
of differing environments worldwide.

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The standard version of the MK:427 has a 4-20mA current loop which outputs a current level,
expressed in milliamperes that is proportional to the sound level with either a 'Fast' or 'Slow' Time
Weighting. The choice of time weighting is a factory set option made at the time of purchase.
The MK:427 has, as standard, an electrostatic actuation system which allows for remote, automatic
and regular verification of the system performance to ensure accurate measurements. See the
Calibration section of the manual on page 12 for more details.
This manual details a version of the MK:427 with both the 4-20mA loop output and the electrostatic
actuator option fitted.
The output is always weighted with the ‘A’ frequency weighting which is the most commonly used
frequency weighting for the measurement of environmental and industrial noise levels.
The 4-20mA current loop output is ideal for integration to many process measurement and control
systems where your own system loggers and software can provide an accurate representation of the
'live' noise levels and also store data.
Your own interface system will need programming with a simple formula which is outlined on your
Factory Configuration Information sheet.
For Example:
For a unit with a range of 34 to 104 dB
Sound Pressure Level dB = (10 x I)-10
(Where I is the output current in mA)
Therefore, in this example an output current of 7.23mA would represent a noise level, LA, of
62.3dB(A) as shown below:
dB(A) = (10 x 7.23) -10
dB(A) = 72.3 –10
dB(A) = 62.3
Please check with our technical department if you need confirmation as to the settings of your
equipment or if you need any other technical guidance.
Tel: + 44 1733 667100
email: [email protected]

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MK:427 Microphone Unit System Diagram

MK:427 Environmental Noise Microphone
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Mounting Information
The unit is supplied with a standard mounting kit to enable the unit to be fixed to a pole or similar.
3 x Jubilee clips
2 x U-Bolts with washers & nuts
The optional CM:427 mounting kit can be used to mount the MK:427 onto a building or other fixed
structure.

MK:427 Environmental Noise Microphone
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General Guidance
Positioning your MK:427 Noise Sensor
Every site and application is different but here are some basic guidelines for effective positioning of
your Noise Sensor:
It is usually worth conducting a noise survey, or referring to measurement data from a
recent noise survey to understand the noise profiles for the area.
Install the sensor at a location nearby to where the environmental noise is most likely to
cause annoyance to neighbouring residential areas or other sites.
Legislation often specifies where measurements should be made, for example at property
boundaries or at a complainant’s property.
Try to mount the unit away from obstacles and building walls.
The microphone should always be a minimum of 1.2 –1.5m above the ground level.
Avoid, where possible, overexposed areas where high wind speeds will affect the noise level
readings.

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Operation
External Connections
External connection to the MK:427 is made via the supplied 10m cable with the following wiring
connections:
Power Supply
Red & Orange: Nominally +12VDC
Black & Green & Braid & Blue: Power Ground (0V)
Notes:
The nominal power supply voltage is +12VDC.
The MK:427 can operate with a power supply within the range of +9VDC to +36VDC
The maximum current for normal operation is 75mA.
The power supply for the unit must be independent of the isolated loop circuit.
Isolated Loop circuit
White: Loop output
Brown: Loop input
Notes:
The nominal output current is 0.1mA/dB over the range of the instrument.
The maximum allowable loop voltage is 30V.
Actuator control
The electrostatic actuator is
Yellow: Any voltage of between +5V to +12V = Actuator on
Any voltage of between 0V to +0.3V = Actuator off
Green: Ground (0V). Connect to power supply ground (0V)