Cirrus research CR511E Acoustic Calibrator User Manual
- June 5, 2024
- Cirrus research
Table of Contents
Cirrus research CR511E Acoustic Calibrator
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.
Overview
Accurate calibration of Sound Level Meters and Sound Measurement equipment is
essential before and after each measurement to ensure the validity of any
values recorded.
The CR: 511E Acoustic Calibrator provides a cost effective yet accurate
means of achieving this requirement.
The CR: 511E unit can be used for all microphones suitable for this kind
of calibration. It has the ability to accept different cavity adaptors. The
CR:511E has a nominal cavity diameter of 1.125 inches. A standard QC: 3
adaptor allows the unit to be used with a ½ inch microphone. Other adaptors
are available. The approval by the German test office PTB is valid for the 1/2
inch adaptor.
The CR: 511E provides two reference levels of 94dB(1 Pa) and 104 dB (3.16
Pa). It is therefore possible to judge the linearity of the instrument and to
calibrate at high background noises.
The frequency is 1000 Hz, therefore the frequency weighting of the instrument
has no influence on the accuracy of the calibration.
The CR: 511E Acoustic Calibrator meets the requirements of IEC 942, it
corresponds to type 1L, which means, it is type 1 if the correction values for
the air pressure are observed.
Operation
The CR:511E acoustic calibrator has provision for the calibration of a variety
of microphones of various diameters. The nominal cavity has a diameter of
1.125 inches. A standard QC:3 adaptor allows the unit to be used with a ½ inch
microphone. Other adaptors are available for 1 inch, 1/4 inches, 20 mm and 10
mm.
The CR:511E unit is supplied with one adaptor as standard. Typically this is
the QC:3 adaptor for ½” microphones. The sound pressure generated by the
calibrators are 94dB and 104dB.
However, when calibrating a microphone which is to be used for free field
measurements, a small correction may be necessary to compensate for the
difference between the microphone’s free field response at ‘zero degrees’ or
‘head-on’ incidence and the pressure level generated by the calibrator. The
correction is typically -0.3dB for ½ inch microphones (making the effective
calibration level 93.7dB). A second correction is required if the barometric
pressure is not 1013 hPa. A table shows the correction values for the standard
microphones of Cirrus Research plc
In order to adapt different microphones to the CR:511E at the accuracy stated
the adaptors available from Cirrus Research plc should be used. For half inch
microphones the type Q3 is available, with this adaptor the calibrator can be
certified officially.
Calibrating a Sound Level Meter
Ensure that the batteries in both the calibrator and the Sound Level Meter are
in good condition. Do not attempt to calibrate the Sound Level Meter if
battery levels are low.
Push the microphone of the Sound Level Meter, with the appropriate adaptor if
required, into the cavity at the end of the calibrator. Ensure the microphone
is fully inserted into the cavity and is past the ‘O’ ring seal. The
microphone should be parallel to the body of the calibrator.
Turn on the calibrator and select the reference level required. In most
situations, this will be 94dB, although the CR:511E units provide an
additional 104dB reference level. Check which level the Sound Level Meter is
set to accept during calibration. Most modern Sound Level Meters have
electronic calibration with the level adjusted automatically.
Adjust the Sound Level Meter to the correct level where applicable. There are
several factors to be considered when correcting the value generated the
calibrator. These are:
- A correction for the type of microphone capsule.
- A correction for any changes in barometric pressure from 1013mBar (1013 hPa).
MK: 224 microphone capsules which are fitted to the majority of Cirrus
Research Sound Level Meters have a correction of -0.3dB when used with the
CR:511E.
The CR: 511E Acoustic Calibrator is designed to be used mainly with ½”
Microphone Capsules. Calibration corrections are listed below for the Cirrus
Research plc ½” Capsules and two microphone capsules commonly used in test
labs: 
Example
An example of the procedure used to calculate the value required is shown
below:
- Level = 94.0dB + Microphone Correction + Barometric/Altitude Correction
- Level = 94.0dB + ( -0.3dB) + Correction for 700mBar
- Level = 94.0dB + ( -0.3dB) + (-0.8dB)
- Level = 92.9dB
Different microphones will have different correction values. Also, the use of different calibrator adaptors may alter the final values required. Please check the operation manual for the Sound Level Meter or microphone concerned for details.
Changing the Battery
The CR: 511E acoustic calibrator uses a single 9v battery. This type of battery is known as 6F22 or NEDA 1604. It is also commonly known as PP3.
- Put a small rod, usually a screwdriver, through the two holes in the end cap and gently pull the cap from the body.
- Pull out the end plate which has the switch and battery holder attached.
- The battery, type 6F22 (PP3) can now be eased out of its holder and replaced. Make SURE you check the correct polarity of the battery, which clips into the press studs on the battery holder.
Battery type
One battery type 6F22 is used. This is called NEDA 1604 in the USA and parts
of Asia. It is often called ‘PP3’ in the UK and the old Commonwealth.
The battery should preferably be an alkaline battery, not an ordinary dry
cell. Whilst an ordinary cell is adequate for operation, the low price of long
life batteries makes their use sensible.
A long life battery is not only more efficient, but is less prone to leak and
damage the calibrator. The material of the end ring and cavity is easily eaten
away by battery leakage. The battery is 9 volts when new and will operate the
calibrator down to about 6 volts.
Performance Information.
Variation with Temperature.
The acoustic outputs of the CR:511E Acoustic Calibrator will alter with
changes in temperature. The tolerances shown below are for reference
conditions of 1013mBar (1013 hPa) and 65% Relative Humidity. 
Barometric Pressure Correction for CR:511E.
The variation due to static pressure may be up to 0.7 dB from the nominal
value and therefore, the static pressure must be known in order to make this
correction. This figure can be obtained e.g. from your local airport. However,
if measurements are required to the highest accuracy, a barometer should be
purchased. The CR:590 Barometer is available for use with the CR:511E Acoustic
Calibrator.
Specification
- Frequency 1kHz ± 1.5%
- Sound Level 94dB & 104dB re 20μPa
- Level Accuracy ± 0.3dB at 23 C and 101.3kPa
- Standardisation IEC 942 Class 1L
- Distortion Less than 2%
- Variation with Temperature To IEC 942 Class 1L
- Variation with Barometric Pressure See Curves or CR:590 barometer
- Operating humidity 10 to 90% rel.hum.
- Operating Temperature -10oC to +50oC
- Storing temperature -20oC to +60oC
- Long Term Drift Better than ±0.1dB
- Effective Volume 40 cm3
- Cavity Diameter 1.125 inch with Q3 Adaptor for ½” Microphones
- Battery 1 x 9v 6F22 (Neda 1604)
- Weight with battery 220g
- Dimensions 135mm x 48mm
Appendix 1 – Free Field Correction
When calibrating a microphone which is to be used for free field measurements,
a small correction may be necessary to compensate for the difference between
the microphone’s free field response at ‘zero degrees’ or ‘head-on’ incidence
and the pressure level generated by the calibrator. The correction is
typically -0.3dB for ½ inch microphones (making the effective calibration
level 93.7dB).
The table below shows the correction values for the standard microphones of
Cirrus Research plc. Calibration corrections are listed below for the Cirrus
Research plc ½” Capsules and three microphone capsules commonly used in
Calibration Laboratories:
Microphone Correction Values
Example
An example of the procedure used to calculate the value for an MK:224
microphone is shown below :
- Level = 94.0dB + Microphone Correction
- Level = 94.0dB + ( -0.3dB)
- Level = 93.7dB
Different microphones will have different correction values. Please check the operation manual for the Sound Level Meter or microphone concerned for details.
CE Certificate of Conformity
Manufacturer:
Cirrus Research plc
Acoustic House, Bridlington Road Hunmanby, North Yorkshire, YO14 0PH United
Kingdom
Telephone +44 1723 891655
Equipment Description
The following equipment manufactured after 1st January 2007:
CR: 511E Acoustic Calibrator
Along with their standard accessories According to EMC Directives 89/336/EEC
and 93/98/EEC meet the following standards
EN 61000-6-3 (2001)
EMC : Generic emission standard for residential, commercial and light
industrial environments.
EN 61000-6-1 (2001)
EMC : Generic immunity standard for residential, commercial and light
industrial environments.
Warranty Information
-
Every new product is provided with a 12-month no-quibble warranty. This covers everything we provide against failure, poor workmanship and accidental damage.
NB – European Union law states a product has to be fit for purpose for 24 months after purchase. This two-year period covers failure and poor workmanship only. -
If the product is calibrated by Cirrus Research or an authorised calibration and service centre, then the initial 12-month warranty is extended by a further 12 months, with the same conditions, for up to 15 years in total.
-
If a product has not been calibrated annually by Cirrus Research or an authorised calibration and service centre, then you may buy back into the warranty scheme for a small fee, plus the cost of calibration. This can only be done once during the life of the product.
-
If a microphone capsule fails under warranty and is physically damaged, we will replace it with a refurbished capsule.
-
If you don’t wish to have a refurbished capsule, then you can trade in your damaged capsule for a new one, which will incur a fee.
Cirrus Research Offices
The addresses given below are the Cirrus Research plc offices. Cirrus Research
plc also have approved distributors and agents is many countries worldwide.
For details of your local representative, please contact Cirrus Research plc
at the address below. Contact details for Cirrus Research authorised
distributors and agents are also available from the Internet Web site at the
address shown below.
United Kingdom
Cirrus Research plc Acoustic House Bridlington Road Hunmanby North Yorkshire
United Kingdom YO14 0PH
Tel: +44 (0) 1723 891655
Email: sales@cirrusresearch.com
website: www.cirrusresearch.com
References
- Noise Measurement Instruments | Cirrus Research plc
- Cirrus Research GmbH - Cirrus Research GmbH
- Cirrus Research Pionnier dans la création d'instruments de mesure acoustique
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