SKF CMAC 2504 User manual

CMAC 2504
Acoustic emission pulse generator
User manual

The CMAC 2504 is a handheld, portable acoustic emission pulse
generator used to inject a known signal into a machine instrumented
with an SKF Acoustic Emission Enveloping (AEE) condition monitor-
ing systems. The system’s response to the signal is used to validate
the installation. The CMAC 2504 generates a pulse train output with
20 V amplitude, 2.0 μs pulse width and a repetition frequency of
~70 Hz. The AEE system response should be an attenuated pulse
train with the same repetition frequency (~70 Hz). The presence of
this response is sufficient to validate an AEE installation.
Features
• Pulse train output with 20 V amplitude, 2.0 μs pulse width and a
repetition frequency of approximately ~70 Hz
• LED indicators for on/off state and also for low battery condition
• Estimated battery life > 100 hours for Lithium PP3 battery
• Automatically turns off after 60 minutes to conserve battery life
• Handheld
• Portable
• Rugged rubber boot
• Carry case
Components
• Acoustic emission pulse generator base unit
• 9 V PP3 Lithium battery with rating 550 to 1 200 mAh
• Protective rubber boot with stand/belt-clip
• Signal cable (BNC to SMB)
• Acoustic emission transducer
• Couplant gel*
• Protective carrying case
* Allergy warning: Couplant gel contains refined peanut oil. Please refer
to the Material Safety Data Sheet (MSDS).
Recommended use
All installations of SKF AEE condition monitoring solutions must be
validated before they can be commissioned. The CMAC 2504 is rec-
ommended for the validation of SKF AEE condition monitoring sys-
tems including SKF Multilog On-line IMx systems equipped with
CMON 2504 AE interface cards and appropriate acoustic emission
sensors. The CMAC 2504 can also be used to optimise sensor loca-
tions in advance of permanent installation by assessing the signal at-
tenuation for different sensor positions using the CMAC 2504 as an
input stimulus.
Storage
When not being used, the CMAC 2504 should be stored in the
provided carrying case. The device has been designed to withstand
temperatures between –40 and +60 °C (–40 and +140 °F) and
humidity levels of 10 to 90% relative (non-condensing) while in
storage. For long term storage (i.e., > 3 months), it is recommended
that the battery be removed from the unit.
Instruction guide
Turning the device On and Off
1 On – Press the red power button on the device membrane to turn
the device on. A green LED, adjacent to the button, will light
indicating that the device is on.
2 Off – Press the red button and hold for at least three seconds. The
green LED will turn off, indicating that the device is powered off.
On/Off button
On state LED
indicator (green)
Low battery LED
indicator (red)
Carrying case.
2

Installing/Replacing the Battery
1 Low battery is indicated by a red LED next to the battery symbol.
2 To replace the battery, remove the protective rubber boot carefully,
taking care not to damage the SMB jack on the top of the pulse
generator.
3 On the back of the unit there is a sliding panel. Push and slide this
panel away from the device to remove it.
4 Remove the old battery.
5 Install the new battery, respecting the polarity indicated on the
device.
Connecting the Cable to the CMAC 2504
1 An SMB-to-BNC cable is provided for connecting the CMAC 2504
with the acoustic emission transducer.
2 Connect the SMB connector to the SMB jack on the CMAC 2504 by
pushing the cable connector gently, but firmly onto the jack.
3 To remove the cable from the CMAC 2504, pull gently, but firmly
on the cable connector.
Connecting the Cable to the Acoustic Emission
Transducer
1 Connect the BNC end of the supplied cable to the acoustic emis-
sion transducer by connecting it to the transducer and twisting to
secure the connection.
2 To remove the cable from the transducer, twist the cable connector
and pull gently, but firmly on the cable connector.
SMB jack on the CMAC 2504 (left) and cable with SMB connector (right).
Acoustic emission transducer (left) and cable with BNC connector (right).
Injecting a Signal
1 Ensure that the CMAC 2504 device is connected to the transducer
and powered on. Ensure the SKF Acoustic Emission Enveloping
condition monitoring system is ready for signal acquisition.
2 Apply a thin, but even layer of couplant to the surface of the
transducer.
3 The metallic surface that the transducer will be applied to should
be flat and smooth and prepared so that all dust, residue and paint
have been removed using sandpaper and surface cleaner (IPA),
thus ensuring direct contact with the metal.
4 Press the transducer onto this surface to inject a signal into it and
hold in place until several data samples of the system response
have been recorded.
Apply couplant to transducer.
Press transducer onto surface.
3

Application Notes
1 Direct contact between the transducer and the metal surface is
important; therefore, where possible, dust, residue and paint
should be removed prior to use.
2 For validating an installation, the transducer should be used to
inject a signal in the vicinity of the acoustic emission sensor being
tested.
3 When injecting a signal into a surface, ensure there is a direct
transmittance path between the acoustic emission sensor and
acoustic emission transducer – there should be no cracks/joints/
nuts/bolts/holes interrupting the path.
Signal injection sites
1
2
3
CMAC 2504 recommended
injection sites
Acoustic emission
sensor
Outer ring
Inner ring
Bearing seal
4 It is recommended that each acoustic emission sensor installation
be validated by injecting a signal using the CMAC 2504 device at
the following locations:
• If the acoustic emission sensors are mounted on the inner ring,
then:
–Immediately adjacent to the acoustic emission sensor in an axial
direction into the inner ring.
–At a position 90° along the inner ring in an axial direction.
–At a position 180° along the inner ring in an axial direction.
• If the acoustic emission sensors are mounted on the outer ring,
then use similar locations, but on the outer ring of the bearing,
that is:
–Immediately adjacent to the acoustic emission sensor in an axial
direction into the outer ring.
–At a position 90° along the outer ring in an axial direction.
–At a position 180° along the outer ring in an axial direction.
4

Example System Response
The figures below show the spectrum (top) and time waveform (bot-
tom) of the acoustic emission response picked up by a CMSS 786M
dual sensor mounted on the axial face of the outer ring of the bear-
ing when a signal was injected by the CMAC 2504 into a location ad-
jacent to the sensor. Note the strong pulse train in the time domain
and also the clear ~70 Hz peak (plus harmonics) in the spectrum.
Spectrum (top) and time waveform (bottom) of the acoustic emission response.
5

®SKF and MULTILOG are registered trademarks of the SKF Group.
All other trademarks are the property of their respective owners.
©SKF Group 2013
The contents of this publication are the copyright of the publisher and may not be reproduced (even
extracts) unless prior written permission is granted. Every care has been taken to ensure the accuracy
of the information contained in this publication but no liability can be accepted for any loss or damage
whether direct, indirect or consequential arising out of the use of the information contained herein.
PUB CM/I4 14131 EN · December 2013
Please contact:
SKF Condition Monitoring Center – Luleå
Aurorum 30, SE-977 75 · Luleå, Sweden
Tel: [phone] · Fax: [phone]
Web: www.skf.com/cm
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