Cirrus Optimus+ User manual

Instrument
Handbook
Opmus+ GPS
Sound Level Meters

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Optimus+ Sound Level Meters – User Manual
About this manual
The instructions in this user manual refer to the operation of Cirrus Research plc Optimus sound
level meters with version 5.0 or higher of the firmware.
The instruments described in this manual are the Optimus+ Red (CR:160 series) and Optimus+
Green (CR:170 series) with GPS functionality.
This manual describes the recommended usage of the Optimus+ GPS. Any warnings will be
indicated by the following symbol:
The additional information required for testing in accordance with IEC 61672 is provided as a
supplementary document, Optimus Sound Level Meters Technical Data Part B, which is available
for download at:
www.cirrusresearch.co.uk/library/user-manuals/
It is not possible to change the way that the instrument measures through the software or
firmware. Any legal metrology aspects of the instrument cannot be affected by any changes
made in the instrument.
The Common Specifications section on page 33 defines which standards relate to the different
functions available in the instruments. Additional approvals and certifications may apply to the
instruments and these will be listed in the Appendices.
More detailed explanations of the audio recording templates, tonal noise detection and the
repeat measurement timers are available to download from the Cirrus website at
www.cirrusresearch.co.uk/library/user-manuals/

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Optimus+ Sound Level Meters – User Manual
Copyright
Copyright © Cirrus Research plc 2010-2021
All rights reserved.
You may re-use this document/publication (not including the Cirrus Research plc logo and other
product logos) free of charge in any format for research, private study or internal circulation
within an organisation. You must re-use it accurately and not use it in a misleading context.
You must not modify text, images or illustrations in any way. The material must be acknowledged
as Cirrus Research plc copyright and you must give the title of the source document/publication.
Where any third-party copyright material is identified you will need to obtain permission from
the copyright holders concerned.
Trademarks
Cirrus Research plc, the Cirrus Research plc Logo, doseBadge, DOSEBADGE, Optimus, the
NoiseTools Logo and the Noise-Hub Logo are either registered trademarks or trademarks of
Cirrus Research plc in the United Kingdom and/or other countries. Microsoft and Windows are
registered trademarks of Microsoft, Inc. All other trademarks acknowledged.
Updates
In the interests of continuous product improvement, Cirrus Research plc reserves the right to
make changes to product specifications without notice.
To understand the latest updates that have been implemented into this product and to download
the most current version of this user manual, visit our website at
www.cirrusresearch.co.uk
Revision 4 | July 2021

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Optimus+ Sound Level Meters – User Manual
Contents
1. Introduction ............................................................................................................................................5
2. First use...................................................................................................................................................7
2.1 Inserting the batteries ............................................................................................................................................ 8
2.2 Setting the clock ..................................................................................................................................................... 8
2.3 Calibration .............................................................................................................................................................. 9
3. Making a measurement.........................................................................................................................11
4. Operations in more detail......................................................................................................................12
4.1 NoiseTools ............................................................................................................................................................ 12
4.2 Keypad and controls ............................................................................................................................................. 12
4.3 Connectors ........................................................................................................................................................... 13
4.4 Screen saver ......................................................................................................................................................... 14
4.5 Display .................................................................................................................................................................. 15
4.6 Audio recording .................................................................................................................................................... 17
4.7 Timers................................................................................................................................................................... 18
4.8 Back erase/pause ................................................................................................................................................. 18
4.9 Memory................................................................................................................................................................ 19
4.10 Restore factory settings........................................................................................................................................ 19
4.11 Windshield............................................................................................................................................................ 19
4.12 Bluetooth.............................................................................................................................................................. 20
4.13 GPS ....................................................................................................................................................................... 20
5 Getting to know your instrument - features & capabilities....................................................................25
5.1 Views .................................................................................................................................................................... 25
5.2 High-level noise measurement............................................................................................................................. 28
6Menus ...................................................................................................................................................29
7Additional information..........................................................................................................................32
8Appendices............................................................................................................................................33
8.1 IEC 61672 test data............................................................................................................................................... 33
8.2 Common specifications ........................................................................................................................................ 33
8.3 Views .................................................................................................................................................................... 36
8.4 Stored measurements .......................................................................................................................................... 39
8.5 Electrical outputs.................................................................................................................................................. 42
9 Acoustic calibrator information.............................................................................................................44
9.1 Setting up the calibrator....................................................................................................................................... 44
9.2 Calibrating a sound level meter............................................................................................................................ 44
9.3 Changing the battery ............................................................................................................................................ 45
9.4 Specifications........................................................................................................................................................ 46
9.5 Technical information........................................................................................................................................... 46
10 EU Declaration of Conformity................................................................................................................48
11 Product guarantee and extended warranty...........................................................................................49

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Optimus+ Sound Level Meters – User Manual
1. Introduction
Welcome to your Optimus+ GPS sound level meter. This next-generation instrument from Cirrus
Research plc is powerful yet simple to use and is capable of a wide range of noise measurement
functions.
Microphone capsule
Microphone
preamplifier
Preamplifier locking ring
Ambient light sensor
Display
Soft keys
Control keys

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Optimus+ Sound Level Meters – User Manual
Battery cover screw
Battery cover
Tripod mount
Power button

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Optimus+ Sound Level Meters – User Manual
2. First use
Your sound level meter has been shipped in reusable packaging that should be retained for safe
shipment when returning the instrument for calibration or servicing.
All Optimus+ GPS sound level meters come with the following standard accessories:
• MV:200 microphone preamplifier
• Microphone capsule (attached to the preamplifier)
• Wrist strap
• 4 x AA batteries
• User manual
• Windshield
You may have other accessories, depending on your package.
When connecting the preamplifier, please take great care to only turn the locking ring at the
base.
Twisting the preamplifier body is likely to cause serious damage. The microphone capsule is also
delicate, and care needs to be taken when handling it.
Damage caused by misuse is not covered by the warranty for the instrument.

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Optimus+ Sound Level Meters – User Manual
2.1 Inserting the batteries
Your sound level meter is powered by 4 x AA alkaline batteries (also called MN1500 or LR6).
We recommend that you use alkaline batteries to give the best performance.
Remove the battery cover by loosening the captive locking screw (as shown in the diagram
below).
Please look carefully at the diagram inside the battery compartment that shows the correct
polarity. After inserting the batteries in the correct orientation, replace the cover and tighten the
locking screw.
The instrument is switched on by pressing and releasing the on/off button on the left-hand side
of the case. After the bootup screen has been displayed, your sound level meter will show the
last view you used.
2.2 Setting the clock
Your instrument stores the date and time with all measurements to help when analysing results
and ensuring the accuracy of the data. It is important to check that the instrument’s clock is
correctly set before starting a measurement session. It is visible on the top-right corner of the
screen.
To set the clock, press the ‘menu’ button after the instrument has been turned on. Select the
‘Set Clock’ menu and follow the instructions on-screen.

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Optimus+ Sound Level Meters – User Manual
Please note that the clock might need to be set again if the instrument is stored without batteries
for a prolonged period.
2.3 Calibration
All noise measuring instruments should be calibrated before each use because the microphone
is susceptible to minor damage, even from small knocks.
The calibration process applies corrections (if needed) to your instrument’s readings, to ensure
that your measurements are as accurate as possible.
Calibration should also be carried out at the end of a measurement session to make sure that
nothing has happened to the instrument during the session.
To calibrate your sound level meter, carefully push the microphone into the cavity at the end of
the calibrator. Ensure the microphone is fully inserted into the cavity and is past the ‘O’ ring
seals.
Ensure that the small bleed hole next to the microphone cavity on the calibrator is not blocked,
as this could cause damage to the microphone.
Take care not to use a twisting motion when pushing the microphone into the calibrator, as this
is likely to cause damage to the preamplifier.
Press the ‘on’ button on the end of the calibrator. Press the calibrate button on your sound level
meter.

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Optimus+ Sound Level Meters – User Manual
The instrument will measure the sound level from the acoustic calibrator to determine if it is
within the required tolerance and levels. The calibration level must be stable to within ±0.075
dB for 5 consecutive seconds, for calibration to be successful.
When calibration is complete, your instrument will display the level along with the correction or
adjustment made.
Your sound level meter is pre-set with the correction values needed for Cirrus Research
microphone capsules, so no manual adjustment is required. The calibration level you should
expect is 93.7 dB.
Refer to page 44 for detailed operating information for the CR:514 and CR:515 acoustic
calibrators.

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Optimus+ Sound Level Meters – User Manual
3. Making a measurement
Press the ‘start’ key to begin recording (on data logging instruments with the VoiceTag function
switched on, the VoiceTag screen will show – press ‘skip’ to move on without recording a note).
Your sound level meter is now measuring and recording noise data for all available functions,
regardless of your selected view, and the red animated running icon will show in the top left of
the information bar.
The measurement can be paused by pressing the ‘pause/stop’ soft key.
Press once to pause/back-erase and twice to stop, or alternatively press and hold for three
seconds to stop.
The pause/back-erase function is only available if this has been enabled in the instrument menu
(more information on page 18).
To stop the measurement, press the ‘stop’ key. The instrument will change from measurement
to review mode, and your data is stored and ready to review and download. For instruments
without data logging, only the last recorded measurement is available for review.

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4. Operations in more detail
Please note: from this chapter on, the manual describes capabilities which are
available on different models within the Optimus range. This includes the
CR:16XX and CR:17XX GPS-enabled instruments.
If you are unsure which capabilities your instrument has, you can check by looking at the general
view/page 5 (and 6 on some models).
4.1 NoiseTools
All Optimus+ GPS sound level meters can be used with the licence-free NoiseTools software,
which can be used to configure the instrument (some options are only configurable within
NoiseTools and not on the instrument – it will be made clear in the text where this is the case).
NoiseTools is also a powerful platform for storing, analysing and organising your data, and can
produce reports for publication. VoiceTag notes and audio recordings can only be played back
through NoiseTools.
4.2 Keypad and controls
Your sound level meter is controlled via the four arrow keys (up, down, left and right), centre
select key and three soft keys. The soft keys change their function depending on the mode that
the instrument is in. The soft key function is shown above the button on the display.
The left and right keys move between the views and the up and down keys move between the
pages of each view.
The function of the centre button varies depending on the screen being viewed, and duplicates
one of the soft keys. Its function includes ‘menu’, ‘select’, ‘OK’ and ‘exit review’ of measurements.
Soft keys
Centre button
Arrow keys

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Optimus+ Sound Level Meters – User Manual
The ambient light sensor on the front of the instrument will illuminate the keypad and adjust the
brightness of the display automatically when the light level fails.
If the pause function has been activated (described on page 18), the right soft key switches
between pause and stop. Press once to pause/back-erase the measurement, and twice to stop
the measurement. Alternatively, press and hold the button for three seconds to stop the
measurement.
4.3 Connectors
The connectors used by your sound level meter to communicate with a PC and NoiseTools are
at the bottom of the instrument under a protective cover.
Your sound level meter can be powered via the multi-pin connector on the bottom of the
instrument. Power can be connected using a ZL:171 Optimus power input cable (2.1 mm power
jack, 2 m) or via a ZL:176 Optimus 12 V battery pack cable.
The instrument can also be powered from an external source, such as a USB connection to a PC
or via a USB power supply.
USB connection
Multi I/O interface
RS232 and DC output

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An AC output is available on the instrument via the 3.5 mm jack socket. The output is
unweighted, and the output level can be adjusted using the options in the AC-out menu.
This output can be used with external instrumentation. See page 42 for details of the electrical
outputs.
4.4 Screen saver
If no keys are pressed for six minutes the display will dim to preserve battery and screen life and
reduce power consumption. After 30 minutes with no key presses, the display will switch off
completely and the keypad will flash every two seconds to show that the instrument is still
powered. The screen dim and screen saver functions will operate during measurements as well
as when the instrument is not measuring. Press any key to turn the display back on.
The time intervals for the screen dim and screen saver are configurable in NoiseTools.
External power via USB External power via multi-pin connector

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4.5 Display
The instrument uses a high-resolution colour screen to show a clear and easy-to-read display of
all the information you need.
4.5.1 Information bar
The information bar shows icons when functions are active. Examples of the icons are shown
in the diagram above.
4.5.2 Navigation bar
The navigation bar shows which view or menu you are looking at.
4.5.3 Measurement display
In addition to primary and secondary functions, the display features an analogue bar on the left
of the screen, which shows real time A-weighted sound level.
At the bottom of the screen is the page information for your view, i.e. 1 of 3.

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4.5.4 Status bar
When the instrument is not measuring, the status bar shows the date and time. When it is
measuring, it shows the elapsed time and in review mode, it shows the measurement number
and the total number of measurements stored.
4.5.5 Overload and under-range indication
Overload is indicated by a red arrow (↑) shown in the information bar.
Overload is also indicated by the word ‘overload’ and under-range is indicated by the word
‘under range’ (in the chosen language) on the display. On the sound level view and Leq view, the
indicators are situated beneath and to the left of the large number.
When a measurement is not in progress, the indicator is shown for at least one second, so that
very short transient overload or under-range conditions are visible to the operator.
When a measurement is in progress, the overload indicator stays on until the measurement is
stopped or reset.
In some circumstances the overload and under-range indicators will be shown simultaneously.
In this case the text will be abbreviated to save space.
Note that if any displayed decibel value on the sound level view or Leq view is below 14.0 dB,
the value will be replaced by dashes (‘---’). These levels are typically below the noise floor of the
microphone capsule and so will only be encountered during electrical testing.
4.5.6 ‘Bluescreen’
Under rare circumstances when the instrument encounters a condition it cannot recover from,
a ‘bluescreen’ error message will show with an error code. If this should happen to your
instrument, please make a note of the code so engineers at Cirrus Research can diagnose your
problem accurately. After writing down the code, pressing the right key will clear the screen and
the instrument can be used as normal.
4.5.7 Battery indicator
The status of the batteries is shown in the battery level indicator. When the batteries need
replacing, the indicator will turn red.
4.5.8 Low battery indication while switching on
If the start-up screen flashes quickly when you press the ‘on’ button, the batteries have
insufficient power to start, and need replacing.

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4.6 Audio recording
Audio recording can be started manually using the audio soft key or automatically using the
audio triggers.
This starts the instrument recording raw WAV data at a quality that can be set in the menu
(standard, high or studio).
Details of the audio triggers can be found in Technical Note 28 - Audio Recording with the
Optimus Green sound level meters. Please refer to the Cirrus Research plc website at
www.cirrusresearch.co.uk/library/optimus.
Pressing the audio key again stops the recording. There is no maximum duration of an audio
recording set by default, but this can be changed in NoiseTools, and the parameters for the audio
triggers can be configured in NoiseTools.
The audio recording includes a 10 second back buffer (on the standard quality setting). When
triggering a recording manually, it is very difficult to record the beginning of a sound that catches
your attention.
The back buffer will cover the time it takes you to respond and press ‘record’. 10 seconds is the
default duration, which can be changed in NoiseTools.
The time history display and analogue bar turn blue when audio recording is running and revert
to green when it has stopped.
Starting and stopping audio recordings during a measurement does not affect the noise
measurement data being recorded.
Please note, VoiceTags are recorded BEFORE the measurement starts and are for spoken notes
only, not for analysis of recorded sounds.

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4.7 Timers
The single and repeat timers allow you to make precisely timed measurements over pre-set or
custom defined durations, which are set on the instrument using the storage options menu (see
next chapter).
The repeat timer allows measurements to be stopped and started automatically over a long
period of time. The instrument can still be stopped and started manually when the repeat timer
is active.
The repeat timer is synchronised to the real-time clock, so if you choose a 30-minute duration,
the measurement will begin on the hour and at 30 minutes past. When the measurement ends,
a new one will begin and last for the next 30-minute interval.
If the instrument is paused when an automatic timer begins, the new timed measurement will
also be paused.
The single timer allows measurements to automatically stop after a pre-defined period. If you
set the single timer duration to 15 minutes and enable the single timer option, then all
measurements will automatically stop after 15 minutes.
(Firmware version 2.8 and above) The single timer can also be set using the NoiseTools software
to halt when the measurement is paused. This allows a measurement to have an exact ‘non-
paused’ duration. For example, if you set the single timer to two minutes and pause the
measurement for 30 seconds, the measurement will automatically stop after two minutes and
30 seconds instead of after two minutes.
4.8 Back erase/pause
4.8.1 Pause
Your sound level meter provides pause and back-erase functions, which can be used during a
measurement.
When the pause function is enabled in the menu, the ‘stop’ button is replaced by the ‘pause/stop’
button. This also enables the back-erase function, the duration of which can be set in the menu.
Please note that the measurement will automatically resume after five minutes in pause mode.
4.8.2 Back-erase
The back-erase function allows a section of the measurement to be removed from the data used,
to calculate the overall values.

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An example of this would be if, during the measurement of cars on a road, a large truck passed
by the measurement location. If the intention was only to measure cars, the truck can be
excluded from the overall measurement data by pressing the ‘pause’ button and then using back
erase to remove a pre-set section of noise.
The time that the ‘pause’ button was pressed, along with the back-erase duration, will be
excluded from the calculation of the overall noise values such as the Leq, Lmin, Lmax, LPeak, and
the 1:1 and 1:3 octave band overall values.
The duration of the back erase can be set to between one and 30 seconds using the menu and
can also be configured in the NoiseTools software. If the pause function is disabled, the back-
erase function is also disabled.
4.9 Memory
The instrument has 4GB of memory as standard. This is partitioned into two sections, one to
record time history and one for audio (VoiceTags and audio recordings). The space allocated to
each can be configured in NoiseTools.
The free space in the memory is shown in the general view as days or hours available for both
time history and audio. When either partition is full, the instrument will overwrite the oldest data
in that partition.
To clear the memory and permanently delete all stored data, choose the ‘clear memory’ menu
page and follow the instructions on-screen. Before permanently erasing the data, you will be
asked to press ‘OK’ to confirm.
4.10 Restore factory settings
This is in the ‘Advanced Options’ menu and restores the instrument to the default options for all
user-definable settings in the menus, and clears the calibration offset. For settings such as
‘language’ where there is no default, the instrument will return to the option it was shipped with.
Follow the on-screen instructions, and press ‘OK’ to confirm. This does not delete any stored
measurements.
4.11 Windshield
The instrument can be used with a UA:237 90mm foam windshield, which will reduce the noise
levels generated by air turbulence over the microphone capsule. It can also help protect the
microphone capsule from dust and fluids, which can affect the performance of the instrument.

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4.12 Bluetooth
The instrument can be connected to a Bluetooth low-energy mobile device to allow control, live
view and overall measurement download. To connect to a device, download the dBactive
application from your smartphone’s app store. On the instrument, go to the ‘Advanced Options’
menu and select the ‘Bluetooth’ page. Enable Bluetooth.
The connection between the mobile device and the instrument requires pairing; this prevents
any unauthorised connections being made.
Run the app on the mobile device and scan for any devices. Select the instrument you wish to
connect to. A pair request will be asked for; the pair key is displayed on the Bluetooth page of
the instrument. Enter this into the mobile device.
The Bluetooth symbol in the information bar turns green when connected.
Please note: Bluetooth on the instrument is connected to Port 2, meaning that it cannot be
enabled at the same as the GPS function.
4.13 GPS
Your Optimus+ GPS sound level meter comes equipped with GPS functionality.