Instruction Manual
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meissner Str. 58 - D-01445 Radebeul
Tel. +49-351 836 2191 Fax +49-351 836 2940
Email: Info@MMF.de Internet: www.MMF.de
Human-
Vibration
Analyzer
VM31
(Valid from version xxx.016)
Published by:
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meißner Str. 58
D-01445 Radebeul
Tel. +49-351-836 2191
Fax +49-351-836 2940
Email Info@MMF.de
Internet www.MMF.de
Note: The latest version of this manual can be found at http://www.mmf.de/product_literature.htm
Specification subject to change.
© 2014 Manfred Weber Metra Mess- und Frequenztechnik in Radebeul e.K.
Full or partial reproduction subject to prior written approval.
Jan/ 19 #194
Contents
1. Purpose.................................................................................................................2
2. The Device at a Glance......................................................................................... 2
3. Fundamentals of Human Vibration Measurement................................................3
3.1. Introduction...................................................................................................3
3.2. EU Occupational Health Directive 2002/44/EC............................................4
4. Human Vibration Measurement with the VM31...................................................7
4.1. Batteries.........................................................................................................7
4.2. Switching on and Connecting the Sensor......................................................8
4.3. Hand-Arm Measurement with the VM31......................................................9
4.3.1. Measuring Points for Hand-Arm Vibration............................................9
4.3.2. VM31 Settings.....................................................................................10
4.4. Whole-Body Measurement with the VM31.................................................12
4.4.1. Measuring Points for Whole-Body Vibration......................................12
4.4.2. VM31 Settings.....................................................................................13
4.4.2.1. Whole-Body Measurement with RMS Values..............................13
4.4.2.2. Whole-Body Vibration Measurement with VDV Values..............18
4.4.2.3. Seat Effective Amplitude Transmissibility (SEAT)......................18
5. General Vibration Measurement.........................................................................19
6. Data Logger........................................................................................................21
7. Frequency Analysis............................................................................................22
8. Data Memory......................................................................................................23
8.1. Measurement Data Memory........................................................................23
8.2. Logger Data Memory..................................................................................23
8.3. FFT Data Memory.......................................................................................24
9. Keypad Lock......................................................................................................24
10. Device Settings.................................................................................................24
10.1. Sensor Calibration.....................................................................................24
10.2. Time and Date...........................................................................................24
10.3. Shut-off Timer...........................................................................................25
10.4. Battery Type..............................................................................................25
10.5. Display Brightness....................................................................................25
10.6. Menu Language.........................................................................................25
10.7. Default Settings.........................................................................................26
11. Reset Key..........................................................................................................26
12. Connection to a PC...........................................................................................26
13. Data Transfer to a PC........................................................................................27
13.1. Opening the Excel File vm31.xlsm...........................................................27
13.2. Data Import to Excel.................................................................................28
13.3. Calculation of Vibration Exposure A(8) and VDV(8)...............................28
13.4. FFT Data Import to Excel.........................................................................29
14. Firmware Update..............................................................................................30
15. Calibration........................................................................................................ 32
16. Technical Data..................................................................................................33
Appendix: Warranty
Declaration of CE Conformity
1
Thank you for choosing a Metra Vibration Measurement device!
1. Purpose
The VM31 has been developed, particularly, for the measurement and analysis of
human vibration. Other fields of application include machine condition monitoring,
building vibration measurement and quality control.
In combination with a triaxial accelerometer, hand-arm and whole-body vibrations
can be measured in compliance with ISO 5349, ISO 2631 and the EU Directive
2002/44/EC. A fourth measuring channel can be used, for example, for SEAT measurements (seat effective acceleration transmissibility).
The VM31 meets the requirements for human vibration meters in compliance with
ISO 8041. In the development of the VM31 value was placed on simple operation
and compact design.
In addition to its application as human vibration meter the VM31 can also measure
machine vibration according to ISO 10816-1/2/3/5/6/7. Measuring ranges for acceleration, velocity and displacement are available.
2. The Device at a Glance
2
Figure 1: Controls, connectors and display
3. Fundamentals of Human Vibration Measurement
3.1. Introduction
Vibrations affecting the human body are called human vibration. The main purpose
of measuring human vibration is the prevention of health risks and the evaluation of
comfort, for example in vehicles.
Two categories are distinguished:
• Hand-Arm Vibrations, which are induced via the hands into the body. They
may cause, for example, circulatory disorder, bone, joint or muscle diseases.
• Whole-Body Vibrations, acting via the buttocks, the back and the feet of a sit -
ting person, the feet of a standing person or the back and the head of a recumbent
person. Such vibrations may cause backache or damage to the spinal column.
Both types of human vibration measurement are described in international standards:
• ISO 5349 - Measurement and evaluation of human exposure to hand-transmitted
vibration
• ISO 2631 - Evaluation of human exposure to whole-body vibration
(also ASA/ANSI S3.18)
• ISO 8041 - Human response to vibration. Measuring Instrumentation
• ISO 8662 - Hand-held portable power tools - Measurement of vibrations at the
handle
• ISO 20283-5 - Guidelines for the measurement, reporting and evaluation of vi-
bration with regard to habitability on passenger and merchant ships
• ISO 10056 - Measurement and analysis of whole-body vibration to which pas-
sengers and crew are exposed in railway vehicles
• ISO 10326 - Laboratory method for evaluating vehicle seat vibration
• ISO 28927 - Hand-held portable power tools - Test methods for evaluation of vi-
bration emission
Practical advice for measurement and evaluation of human vibration can be found in
VDI 2057.
The subject of human vibration has gained particular importance in Europe since the
directive 2002/44/EC came into effect. It specifies the duties of employers with regard to workers protection.
3
3.2. EU Occupational Health Directive 2002/44/EC
The following text is an abstract of Directive 2002/44/EC of the European Parliament and of the Council dated June 25, 2002. The complete text can be downloaded
from http://eur-lex.europa.eu/
The directive specifies minimum requirements for the protection of workers from
the risks arising from vibrations. Manufacturers of machines and employers should
make adjustments regarding risks related to exposure to vibration.
The directive lays down the following limit values:
Hand-Arm, RMS Whole-Body, RMS Whole-Body, VDV
Exposure action
value
2.5 m/s² 0.5 m/s² 9.1 m/s
1,75
Exposure limit 5 m/s² 1.15 m/s² 21 m/s
1,75
Table 1: Limits to EU directive 2002/44/EC
Once the exposure action value is exceeded, the employer shall establish and implement a program of technical and organizational measures intended to reduce to a
minimum exposure to mechanical vibration, taking into account in particular:
• Other working methods that require less exposure to mechanical vibration
• Appropriate work equipment of ergonomic design, producing the least possible
vibration
• Provision of auxiliary equipment that reduces the risk of injuries, such as protec-
tive gloves or special seats
• Appropriate maintenance programs for work equipment
• Design and layout of workplaces
• Adequate information and training to instruct workers to use work equipment
correctly and safely
• Limitation of the duration and intensity of the exposure
• Work schedules with adequate rest periods
• Provision of clothing to protect workers from cold and damp
In any event, workers shall not be exposed above the exposure limit value. If this
should be the case, the employer shall take immediate action to reduce exposure below the exposure limit value.
The methods used may include sampling, which must be representative of the per sonal exposure of a worker to the mechanical vibration in question.
The assessment of the level of exposure to vibration is based on the calculation of
daily exposure A(8) expressed as equivalent continuous acceleration over an eighthour work period. For the determination of A(8) it is not necessary to measure over
eight hours. It is sufficient to make short-term measurements during representative
work steps. The results are normalized to eight hours. Daily exposure is calculated
as follows:
4
A(8)=a
we
√
T
e
T
0
Equation 1
where
A(8) is the daily exposure
a
we
is the energy equivalent mean value of the frequency weighted acceleration
during exposure, which means
- For Hand-Arm Vibration the X/Y/Z vector sum of Wh frequency weighted RMS values (Equation 2)
aw=√a
wx
2
+ a
wy
2
+a
wz
2
Equation 2
- For Whole-Body Vibration the highest of the three RMS values
awx, awy and a
wz
with the following frequency and magnitude weightings:
- X and Y with weighting filter Wd and weighting factor 1.4
- Z with weighting filter Wk and weighting factor 1.0
Te is the total duration of exposure during one work day
T
0
is the reference duration of 8 hours
Daily exposure may consist of several partial exposures with different vibration
magnitudes. This can be the case if there are longer interruptions in the work
process, if the work equipment or its way of use is changed. A partial exposure section should have a roughly constant magnitude and less than 10 % interruptions. Resulting daily exposure is calculated as follows:
Hand-Arm Vibration:
A(8)=
√
1
T
0
∑
i=1
n
a
wi
2
T
ei
Equation 3
where
A(8) is the daily exposure
a
wi
is the energy equivalent mean value of the Wh frequency weighted acceleration of partial exposure section i
n is the number of partial exposure sections
T
ei
is the duration of exposure i
T
0
is the reference duration of 8 hours
Whole-Body Vibration:
Separate daily exposures need to be calculated for X/Y/Z. The highest value is used
for the evaluation, i.e. compared with the limits of Table 1.
Ax(8)=
√
1
T
0
∑
i =1
n
a
wxi
2
T
ei
Equation 4
5
Ay(8)=
√
1
T
0
∑
i=1
n
a
wyi
2
T
ei
Equation 5
Az(8)=
√
1
T
0
∑
i=1
n
a
wzi
2
T
ei
Equation 6
where
A
x/y/z
(8) are the daily exposures of directions X/Y/Z
a
wx/y/zi
are the energy equivalent mean values of the frequency weighted accelerations
in the directions X/Y/Z during partial exposure section i with the following
frequency and magnitude weightings:
- X and Y with weighting filter Wd and weighting factor 1.4
- Z with weighting filter Wk and weighting factor 1.0
n is the number of partial exposure sections
T
ei
is the duration of exposure i
T
0
is the reference duration of 8 hours
The calculations shown above are based on RMS values. An alternative method
uses fourth-power mean values called Vibration Dose Value (VDV) with the measuring unit m/s
1,75
. Table 1 also includes VDV based limit values.
VDV based daily exposure VDV(8) is calculated:
VDV (8)=VDV⋅
4
√
T
exp
T
meas
Equation 7
where
VDV(8) is the daily exposure value
VDV is the frequency-weighted vibration dose value
T
exp
is the duration of exposure
T
meas
is the duration of VDV measurement
Daily exposure may consist again of several partial exposure sections. Separate
daily exposure values are to be calculated for X/Y/Z. The highest one is compared
with the limits of Table 1 for evaluation.
VDVx(8)=
4
√
∑
i=1
n
VDV
xi
4
⋅
T
iexp
T
imeas
Equation 8
VDVy(8)=
4
√
∑
i =1
n
VDV
yi
4
⋅
T
iexp
T
imeas
Equation 9
VDVz(8)=
4
√
∑
i =1
n
VDV
zi
4
⋅
T
iexp
T
imeas
Equation 10
where
6
VDV
X/Y/Z
(8) are the daily exposures of directions X/Y/Z
VDV
x/y/zi
are the frequency-weighted vibration dose values of directions X/Y/Z during exposure section i
T
iexp
is the duration of exposure section i
T
meas
is the duration of VDV measurement during exposure section i
Model VM31 measures Hand-Arm and Whole-Body vibration, the latter as RMS or
VDV values. For the calculation of daily exposure an Excel sheet with a data import
function is provided.
4. Human Vibration Measurement with the VM31
4.1. Batteries
The VM31 is powered from three standard alkaline batteries size AAA (LR03). Alternatively rechargeable
NiMH batteries of type HR03 can be inserted. Precise
operation is guaranteed until the batteries are almost
completely discharged.
Please note that date and time need to be adjusted after
replacing the batteries. All other settings, including
saved measurements, remain stored after removing the
batteries.
To insert the batteries, remove the two screws from the
back cover of the device and open the battery compartment (Figure 2). When inserting the batteries, please ensure that their polarity is correct, (see the engraved
markings inside the compartment).
Important:
• Always use three batteries of the same type and same date of manufacture.
• Remove old batteries from the device, and take out the batteries if the device will
not be used for a long period of time. Otherwise leaking battery acid may cause
severe damage to the device.
Please use your local collection point to dispose of batteries.
Batteries do not belong to the household waste.
A battery indicator can be found in the upper left corner of the display. A green
filled battery symbol indicates a fully charged battery. When the symbol becomes
red only a small portion of power remains and the unit will switch-off soon. Please
also read section 10.4.
If the VM31 is connected to a USB interface, it will be powered via USB to save the
batteries. In this case “Extern” is shown instead of the battery symbol.
7
Figure 2: Batteries
4.2. Switching on and Connecting the Sensor
Switch on the VM31 by pressing the ON/OFF key. The
unit can be switched off again by pressing and holding
the ON/OFF key for one second.
If the sensor has not yet been connected, plug the sensor
cable into the right connector. The VM31 will start
TEDS1 detection each time it is switched on or a sensor is
connected. It supports IEEE 1451.4 TEDS template no.
25 (with or without transfer function). The sensitivities of
X/Y/Z and channel A are displayed for some seconds
(Figure 3). For each channel also the user text of TEDS
(ID) is displayed.
The sensors KB103SVD and KS903.10 supplied by Metra feature TEDS.
Should a connected sensor not have TEDS or an incompatible TEDS version, the
VM31 will open a menu for entering the sensitivities manually (see section 10.1).
The sensitivities entered remain stored as long as the sensor is connected, even if the
batteries are removed.
The warning “SENSOR!” indicates a missing or defective sensor or a broken sensor
cable. Sensor condition is detected by means of the bias voltage at the sensor out put:
< 0.7 V: short circuit
0,7 – 14 V: normal
>14 V: open, e.g. broken cable
Please note that settling time after connecting a sensor is
about 1 minute.
The VM31 is suitable for connecting any low power IEPE
accelerometers which can be operated with a 1 mA supply
current. The internal compliance voltage of the current
sources is 18 VDC.
1 TEDS = Transducer Electronic Data Sheet
8
Figure 3:
TEDS detection
Figure 4: Seat pad accelerometer KB103SVD
Figure 5:
Hand-Arm accelerometer KS903.10
Figure 6:
Sensor socket
(view from outside)
GND
X
Y
Z
Figure 6 shows the contact arrangement of the 4 pin female sensor connector of type
Binder 711.
4.3. Hand-Arm Measurement with the VM31
This section will give you basic instructions for the measurement and evaluation of
hand-arm vibrations based on the standard ISO 5349 and the guideline VDI 2057,
Part 2. Please consult the original documents for detailed explanations.
4.3.1. Measuring Points for Hand-Arm Vibration
The sensors should be attached as close as possible to the gripping points of the
hand, however, they must not interfere with the work process. Measurement should
be performed with the same hand pressure force as used under normal operating
conditions.
Since most machine tool handles do not provide surfaces for the adhesive or screw
attachment of sensors, Metra offers some mounting accessories for curved surfaces.
The adapter model 141 is attached with a plastic cable strap. Model 143 is pressed
onto the handle by the hand.
Close contact between the sensor and the machine is of great importance. Any motion of the sensor would distort the measurement.
Figure 9 shows the axis directions for attaching the sensor to the handle. For cylindric handles the Y direction points in the direction of the handle axis. T he Z axis is
approximately the extension of the third metacarpal bone.
9
Figure 7: Handle adapter 141 Figure 8: Hand-held adapter 143
4.3.2. VM31 Settings
For the evaluation of hand-arm vibration it is recommended to measure both the interval RMS values of
X/Y/Z and their vector sum aW. The VM31 measures
these four values simultaneously. In addition it shows
the maximum running RMS (Maximum Transient Vibration Value, MTVV) which may indicate the presence of shock vibration.
The frequency weighting for hand-arm vibration is Wh.
Figure 11 shows the filter of the VM31 and the tolerance bands to ISO 5349.
10
Figure 10:
Hand-arm measurement
Figure 9: Coordinate system of the hand (from ISO 5349-1)
Figure 11: Hand-arm weighting filter Wh
1 10 100 1000 10000
0,0001
0,001
0,01
0,1
1
10
Wh min ISO 8041
Wh max ISO 8041
Wh VM31
Hz
Press the F3 key to open the main menu and select “Human vibration” / “Hand-Arm
ISO 5349”/„Health“. After returning to the measurement screen (Figure 10) you can
check the settings by pressing F1.
Measurement can begin when the sensor and the worker's hands have been placed
on the handle of the object carrying out the operation. To start the measurement
press the key ► (Reset). This will result in the following:
• the RMS values of X/Y/Z, the vector sum aW and MTVV reset to zero
• the measurement timer restarts.
Pressing Reset before a measurement is mandatory to establish defined start conditions.
The RMS values of X/Y/Z and the vector sum are averaged over the entire measur ing time. That's why fluctuation becomes less the longer the measurement takes. Af ter a while short shock pulses have almost no influence on the displayed results .
Recommended measuring time for hand-arm vibration is at least 30 seconds. The
measuring timer in the upper right corner remains red until 30 second have elapsed.
“OVERLOAD” is indicated instead of the measuring values if the current magnitude is too high. Even if the overload condition was of short duration the measured
interval RMS value may become invalid because of missing samples. An overload
event during the entire averaging time is indicated by “OVL!” in the upper right
corner after the date. This warning can be deleted by pressing the key ► (Reset).
After measurement you may save the results by
pressing the key ▼. Measurement should be continued or finished immediately before pressing the key.
Otherwise the measuring values will drop slowly.
You will be asked to enter two lines of ten capital letters or numbers as a comment (Figure 12). Use the
keys ◄▲▼► to select characters and to change the
input position. Press F1 to change the input line.
Measurement can be finished before entering the
comment because the results have already been saved
when pressing the key ▼.
Measurements can only be saved if a sensor is detected at X/Y/Z and if there is no overload condition.
In these cases the VM31 will display “Sensor error” or “Overload occurred” instead
of saving in order to avoid invalid recordings. If an overload occurred since the last
reset (“OVL!” in upper right corner) the instrument will show a warning “Overload
occurred after last reset! Save anyway?”.
If you want to measure several partial exposures you may do further measurements
(see section 3.2).
For the calculation of vibration exposure A(8) and to store results on a PC the Excel macro file vm31.xlsm is provided.
The fourth channel (A) of the VM31 is not active when hand-arm vibration is mea sured.
11
Figure 12: Comment
4.4. Whole-Body Measurement with the VM31
This section will give you basic instructions for the measurement and evaluation of
whole-body vibrations based on the standard ISO 2631 and the guideline VDI 2057,
Part 1. Please consult the original documents for detailed explanations.
The described method is suitable for all vibrations acting on the human body. It is
not suited for vibration containing occasional shocks or for impacts such car
crashes. Vibrations transmitted via the hands are described separately in the previous section.
4.4.1. Measuring Points for Whole-Body Vibration
Whole-body vibration is usually measured with seat pad accelerometers. These are
triaxial piezoelectric sensors built into a flat rubber pad, which adapt themselves to
the interface between the vibration source and the test person (Figure 4).
The following measuring points are suitable:
On the seat surface under a seated person
On the back rest behind a seated person
Under the feet of a seated person
Under the feet of a standing person
Under the pelvis of a recumbent person
Under the head of a recumbent person
Figure 13 shows the coordinate systems for whole-body vibration to ISO 2631. As
can be seen from the drawing, the Z axis always points in the direction of the spinal
column. The vibration sensor has to be placed accordingly. A special case is measurement at the backrest (see notice below Table 2 on page 13).
Table 2 shows the weighting filters and factors to be used for different postures and
positions.
12
Figure 13: Coordinate systems for whole-body vibration to ISO 2631
Z
Y
Z
Y
Z
X
Y
Z
X
X
Y
X
Y
Z
X
Whole-Body Health Evaluation
Posture Position Direction
Frequency
weighting
Weighting
factor (k)
sitting seat surface
X / Y
Z
W
d
W
k
1.4
1
Whole-Body Comfort Evaluation
sitting
seat surface
X / Y
Z
W
d
W
k
1
1
feet platform
X / Y
Z
W
k
0.25
0.4
backrest
X*
Y
Z*
W
c
W
d
W
d
0.8
0.5
0.4
standing feet platform
X / Y
Z
W
d
W
k
1
1
recumbent
under pelvis
X (vertical)
Y / Z (horizontal)
W
k
W
d
1
1
under head X (vertical) W
j
1
In railway vehicles:
standing
sitting
recumbent
feet platform
seat/backrest/feet
support. surface, pelvis/head
X / Y / Z W
b
1
In buildings:
undefined in buildings X / Y / Z W
m
1
Table 2: Weighting filters and factors for whole-body vibration
* Please note that the Z axis points along the backbone for all measurements. For measure ments at the backrest with a seat pad accelerometer the sensor will always be in a vertical position with Z perpendicularly to the backbone. However, to compensate this the VM31 automatically swaps the X and Z axis for backrest measurement.
4.4.2. VM31 Settings
4.4.2.1. Whole-Body Measurement with RMS Values
For the evaluation of hand-arm vibration it is recommended to measure both the interval RMS values of
X/Y/Z and their vector sum aW. The VM31 measures
these four values simultaneously. In addition it
shows the maximum running RMS (Maximum Transient Vibration Value, MTVV) which may indicate
the presence of shock vibration. MTVV is not always the maximum value of the three single RMS
values of X/Y/Z since these are multiplied with
weighting factors (see table 2) which is not the case
for MTVV.
The following section explains the measurement of
whole-body vibration in terms of health risks. Health
evaluation is done with weighting filter Wd for X/Y
and Wk for Z and with weighting factors 1.4 for X/Y
13
Figure 14:
Whole-body measurement
and 1.0 for Z. Figures 15 and 16 show the frequency response curves of the filters
Wd and Wk in VM31 and the tolerance bands in compliance with ISO 8041.
In addition to health evaluation the VM31 also supports measurements regarding
comfort. This type of measurement uses other postures, sensor positions and different frequency weightings but the general procedure is the same.
Figures 17 to 20 show the frequency response curves of the weighting filters for
comfort measurements.
14
Figure 15: Whole-body weighting filter Wd
0,1 1 10 100 1000
0,0001
0,001
0,01
0,1
1
10
Wd min ISO 8041
Wd max ISO 8041
Wd VM31
Hz
Figure 16: Whole-body weighting filter Wk
0,1 1 10 100 1000
0,0001
0,001
0,01
0,1
1
10
Wk min ISO 8041
Wk max ISO 8041
Wk VM31
Hz
15
Figure 17: Whole-body weighting filter Wb for passenger trains
0,1 1 10 100 1000
0,0001
0,001
0,01
0,1
1
10
Wb min ISO 8041
Wb max ISO 8041
Wb VM31
Hz
Figure 18: Whole-body weighting filter Wc for the backrest of seats
0,1 1 10 100 1000
0,0001
0,001
0,01
0,1
1
10
Wc min ISO 8041
Wc max ISO 8041
Wc VM31
Hz
To start whole-body vibration measurement for the assessment of health risks open
the main menu by pressing F3, and select “Measuring mode” / “Human vibration” /
“Whole-body ISO 2631” / “Health”. From this menu you will return to the measuring screen (Figure 14). You may press F1 to check your settings.
According to ISO 2631-1 there are two evaluation methods for whole body vibration: basic evaluation and additional evaluation. Basic evaluation is performed by
interval RMS measurement. Additional evaluation can be the running RMS method
(MTVV) or the fourth power vibration dose method (VDV) whereupon the latter is
more common. One of the two additional evaluation methods should be applied for
occasional shocks or transient vibration since the basic evaluation methods may un derestimate their effects. A measure for the shock content of vibration is the crest
16
Figure 20: Whole-body weighting filter Wm for persons in buildings
0,1 1 10 100 1000
0,0001
0,001
0,01
0,1
1
10
Wm min ISO 8041
Wm max ISO 8041
Wm VM31
Hz
Figure 19: Whole-body weighting filter Wj for the head of recumbent persons
0,1 1 10 100 1000
0,0001
0,001
0,01
0,1
1
10
Wj min ISO 8041
Wj max ISO 8041
Wj VM31
Hz
factor, i.e. the ratio of peak and RMS. If the crest factor exceeds 9 the additional
evaluation method should be applied.
If the worker being tested is sitting in the right position and vibration exposure has
started measurement can begin.
Select crest factor mode by pressing the ◄ key and start crest factor measurement
by the ► key (Reset). This will
• reset the RMS values of X/Y/Z, the vector sum aW and MTVV to zero
• restart the measurement timer.
Always press Reset before a measurement to establish the defined start conditions.
If the displayed crest factors X/Y/Z are below 9, switch to Interval RMS mode by
pressing the ◄ key. At crest factors above 9 you should measure in addition vibration dose as shown in the next section.
Interval RMS values and crest factors are calculated based on the elapsed measuring
time since the last pressing of the key ► (Reset). This means that the fluctuation of
the displayed values becomes lower the longer the measurement lasts. Single peaks
will have less influence than at the beginning. Relevant for evaluation is only the
value at the end of measurement. The recommended measuring time for whole-body
vibration is at least 2 minutes. To alert you, the timer in the upper right corner re mains red until 2 minutes have elapsed.
The displayed interval RMS for X/Y/Z and vibration total values aw include the
weighting factors (k) according to table 2. The weighting factors are set to 1 for
maximum RMS (MTVV) and vibration dose value (VDV).
“OVERLOAD” is indicated instead of the measuring values if the current magnitude is too high. Even if the overload condition was of short duration the measured
interval RMS value may become invalid because of missing samples. An overload
event during the entire averaging time is indicated by “OVL!” in the upper right
corner after the date. This warning can be deleted by pressing the key ► (Reset).
After measurement you may save the results by pressing the key ▼. Measurement
should be either continued or finished immediately before pressing the key. Otherwise the measuring values will drop slowly. You will be asked to enter two lines of
ten capital letters or numbers as a comment (Figure 12, page 11). Use the keys
◄▲▼► to select characters and to change the input position. Press F1 to change
the input line. Measurement can be finished before entering a comment because the
results will have already been saved by pressing the key ▼.
Measurements can only be saved if a sensor is detected at X/Y/Z and if there is no
overload condition. In these cases the VM31 will display “Sensor error” or “Overload occurred” instead of saving in order to avoid invalid recordings. If an overload
occurred since the last reset (“OVL!” in upper right corner) the instrument will
show a warning “Overload occurred after last reset! Save anyway?”.
If you want to measure several partial exposures you may now do further measurements (see section 3.2).
For the calculation of vibration exposure A(8) and to store results on a PC the Excel macro file vm31.xlsm is provided (see section 13.3).
17
4.4.2.2. Whole-Body Vibration Measurement with VDV Values
The VM31 also allows whole-body vibration to be measured as vibration dose values (VDV). These are integrated fourth power values. VDV is more sensitive to
peaks. The measuring unit of VDV is m/s
1,75
.
Equation 11
Press the key ◄ to switch from RMS to VDV
(Figure 21).
The same weighting filters as for RMS measurement are used. You may press F1 to check your
settings.
The device displays VDV values for the directions X/Y/Z. In addition the highest of the three
axis values (Max. VDV) and the highest VDV
since the last reset (Max. abs.) are displayed.
VDV measurements need to be started by pressing the key ► (Reset).
Measurements can be saved by pressing the key
▼ (see page 17).
For vibration exposure VDV(8) calculation the
duration of VDV measurement should be noted (see section 3.2).
The Excel file vm31.xlsm also allows the calculation of vibration exposure
VDV(8) (see section 13.3).
4.4.2.3. Seat Effective Amplitude Transmissibility (SEAT)
The Seat Effective Amplitude Transmissibility (SEAT) value is the ratio of the vi bration experienced on top of the seat and the vibration that one would be exposed
to when sitting directly on the vibrating floor. Both vibration magnitudes are measured in the vertical direction (Z) only. SEAT values are widely used to determine
the vibration isolation efficiency of a seat.
18
Figure 21: VDV measurement
Figure 23: SEAT measurement with channel A
VDV =
4
√
∫
o
T
a
w
4
(t )dt
Figure 22: SEAT measurement at a drivers seat
The fourth channel (A) of the VM31 in combination with a uniaxial accelerometer
can be used to determine SEAT values. Metra recommends the TEDS accelerometer
KS78.100 for this purpose. It is connected via a sensor cable VM31-A to the left
socket (see 1). The fourth channel is named “A” on the display. The sensitivity of
the KS78.100 will be automatically detected. With a non-TEDS sensor it needs to
be entered manually (see section 4.2).
Select “Whole-body ISO 2631” / “Unweighted” for channels X/Y/Z. Channel A
does not have frequency weightings. Its frequency range (-3 dB) is 0.8 to 250 Hz.
The RMS or VDV of channel A is displayed below channels X/Y/Z (Figure 23).
5. General Vibration Measurement
In addition to human vibration the VM31 measures:
• Vibration acceleration from 0.2 to 1500 Hz and 1 to
1000 Hz,
• Vibration velocity from 1 to 100 Hz, 2 to1000 Hz and
10 to 1000 Hz (for machine vibration to ISO 10816),
• Vibration displacement from 5 to 200 Hz.
Press F3 to open the menu, select “Measuring mode” and
use the keys ▲▼ to select the vibration range.
You can switch the measuring screen from RMS to peak
display by pressing the key ◄. Please note that the RMS
and peak values in the general vibration ranges are measured over the last display cycle (not over a long period).
A display cycle can be between 1 and 4 seconds, depending on the frequency range.
RMS or peak values are shown for each channel in addi tion to combined sum or maximum values (Figure 24). If
these combined values are not needed you can switch to a
mode which only shows the channel values in large characters by pressing key ◄ repeatedly (Figure 25).
There will also be an RMS or peak value for channel A if
you have connected a sensor to this input. Channel A always measures acceleration. Its frequency range depends
on the mode selected for X/Y/Z (Table 3).
If only an uniaxial accelerometer is connected to channel
X (sensor cable with 4 pin connector needed) the VM31
displays the results in large numbers (Figure 26).
Mode X/Y/Z Range X/Y/Z Range A (acceler.)
Acceleration 0.2 to 1500 Hz 0.2 to 1500 Hz
Acceleration 1 to 1000 Hz 3 to 1000 Hz
Velocity 1 to 100 Hz 1 to 250 Hz
Velocity 2 to 1000 Hz 2.5 to 750 Hz
Velocity 10 to 1000 Hz 2.5 to 750 Hz
Displacement 5 to 200 Hz 1 to 250 Hz
Table 3: Frequency ranges of channels X/YZ A
19
Figure 24: 4 channels
and combined values
Figure 25: 4 channels
in large characters
Figure 26: Indication
of 1 channel (X)
Vibration velocity is computed by single integration of the acceleration signal, displacement by double integration. Due to integration there is a strong attenuation at high frequencies which limits the measurable frequencies, particularly for displacement. Low
frequencies, including noise, are strongly amplified. High pass filtering is inevitable. The
frequency response curves of the general vibration ranges can be seen in Figures 27, 28
and 29.
20
Figure 27: Frequency ranges of vibration acceleration
0,1 1 10 100 1000 10000
0,01
0,1
1
10
a: 1Hz – 1kHz
a: 0,1 Hz – 2 kHz
Figure 28: Frequency ranges of vibration velocity
1 10 100 1000 10000
0,0001
0,001
0,01
0,1
1
10
v: 1Hz – 100Hz
v: 2Hz – 1kHz
v: 10Hz – 1kHz*
Vibration quantity and frequency range can be checked by pressing F1.
Below the 3 (or 4) RMS or peak values you can see two combined values which are
calculated from X/Y/Z. These are:
• in RMS mode the vector sum of X/Y/Z (aw(Vec)) and the highest RMS value
(Max. abs.) since the last press of the Reset key ►.
• in peak mode the highest of the currently displayed XYZ peak values (Max.
XYZ) and the highest peak value (Max. abs.) since the last Reset ►.
Maximum values are displayed in the color of the channel where they occurred.
Pressing the Reset key ►
• deletes the maximum values and
• restarts the measuring timer.
Measurements can be saved by pressing the key ▼ (see page 17).
The Excel file vm31.xlsm can be used to transfer the measurements to a PC.
6. Data Logger
The VM31 can automatically record measuring data
for channels X/Y/Z at the speed of the display refresh rate. It can log running RMS or peak values.
Logging can be useful in combination with human
vibration measurement to detect single vibration or
shock events during a longer measuring period. For
example, the log file can help to identify shocks
caused by putting down a machine tool. Such single
events can significantly change the interval RMS
value without being relevant in terms of health risks.
The instrument stores data and time along with the
three values of X/Y/Z. The recorded measurements
21
Figure 30: Starting the data
logger
Figure 29: Frequency range of vibration displacement (upper end due to resolution)
1 10 100 1000
0,0001
0,001
0,01
0,1
1
10
are filtered with the same weighting or band filter used for the displayed measurements. Channel A is not recorded.
Please note that the logged data is calculated only for the last display interval (ap prox. 1 s). For human vibration, however, interval RMS values are measured which
are integrated over the entire measuring time. Thus there will be differences between the displayed and the recorded values.
To start the data logger press F3 to open the main menu, select “Data memory” /
“Data logger” / “Start logging” (Figure 30). You will be prompted to select a file
number. This number will be used later on to identify the log file. The memory can
hold 100 log files. File numbers can be 00 to 99. If the selected file should already contain data you will be asked to
delete it. Now you select whether RMS or peak values are
to be logged. Press OK to leave the menu and to start logging. After a settling time the unit will start to record measurements. The active log mode is indicated in the upper
right display corner by the text “LOG!” (Figure 31).
Logging can be stopped by pressing F3.
Please note that the data logger will be halted while data is transferred via the USB
interface. This may result in missing records.
The automatic shut-off function (see chapter 10.3) is not in use while logging.
The maximum number of records per log file is 32,000 which is sufficient for about
10 hours of continuous recording.
7. Frequency Analysis
The VM31 provides a simple FFT function for the detection of main frequencies. It
displays a 125 line peak spectrum of acceleration.
Press F3 and select “Frequency analysis” to open
the FFT screen (Figure 32). You see the frequency
components of channels X/Y/Z2 in their respective
channel colors.
The line above the diagram shows frequency and
magnitude of the longest spectral line.
The keys ◄► move the cursor. Below the diagram you can see the cursor readout.
Press F1 or F2 to change the frequency range. Four
ranges are selectable:
• 3 to 244 Hz
• 7 to 488 Hz
• 15 to 977 Hz
• 30 to 1954 Hz
By the OK key you can switch between automatic and fixed amplitude scaling. In
the help line you see the function of the OK key when you press it next time. In
most cases automatic scaling will be the best choice.
Pressing the key ▼saves the spectrum. The VM31 memory can hold up to 1000
FFTs (see also chapter 8.3).
2 There is no FFT function for channel A.
22
Figure 32: Frequency analysis
Figure 31: Log indication
8. Data Memory
8.1. Measurement Data Memory
The VM31 memory can hold up to 10,000 data
records. A record includes:
• Date and time
• Comment (20 characters)
• Filter and measuring mode
• Measuring values X/Y/Z and, if available,
channel A and 2 combined values (vector sum
and maximum value)
Saved data can be viewed on the screen. Press F3
and select “Data memory” / “View/delete measurement”. Use the keys ▲▼ to navigate through
the records (Figure 33).
Single records can be erased by pressing ◄.
Erasing means the record is not displayed anymore. Its memory position, however, will not be
released until the entire memory is erased. This
can be done in the menu “Data memory” /
“Delete memory”. Please note that the FFT
records will also be erased.
Stored measurement data can be transferred to a
PC using the Excel macro file vm31.xlsm.
8.2. Logger Data Memory
To view stored logger data press F3 to open the
menu and select “Data memory” / “Data logger”.
In this menu open “View logger data”. Use the
▲▼ keys to select the log file to be opened. The
menu shows date and time of start, the used
recording mode (RMS or Peak), the measuring
mode and the filter settings. Press OK to open a
selected file (Figure 34).
A file can be deleted by pressing F1.
After opening a log file you can view the contained measurements (Figure Fehler: Verweis
nicht gefunden). Use the ▲▼ keys to select a
record. The menu shows the record number and
the total number of records, date and time of
recording and the measuring values X/Y/Z.
Stored logger data can be transferred to a PC using the Excel macro file vm31.xlsm. The file also
provides a graphical output.
23
Figure 33: Data memory
Figure 34: View log files
Figure 35: View logger data
8.3. FFT Data Memory
To view stored FFTs press F3 to open the menu
and select “Data memory” / “View/delete FFT
data”. Use the keys ▲▼ to select the desired
FFT. A cursor function using the keys ◄► is
also available (Figure 36).
Stored FFT data can be transferred to a PC using
the Excel macro file vm31.xlsm. The file also
provides a graphical output.
9. Keypad Lock
To prevent manipulation during ongoing measurement, it can be advantageous to activate the
key lock. This function can be found in the main
menu under “Key lock”
To release the key lock press all four arrow keys ◄▲▼► simultaneously, until the
device displays “unlocked”.
10. Device Settings
10.1. Sensor Calibration
If a connected sensor is not TEDS compatible, the
VM31 will automatically open the menu “Transducer calibration” (see section 4.2). It can also be
opened from the menu “Device settings” to check
or to change the entered sensitivities.
Sensitivities are entered one after another for channels X/Y/Z and, if connected, for channel A. The
sensitivity value is a five-digit number with the
measuring unit mV/ms-2. You find the correct values in the transducer calibration sheet. The decimal
point can be shifted by pressing F1. The allowed
sensitivity range is 0.800 to 12.000 mV/ms-2 or
8.00 to 120.00 mV/ms-2.
10.2. Time and Date
When saving measurement values the date and
time need to be correctly recorded. To set the date
and time, open the main menu by pressing F3 and
select “Device settings”. Within this sub menu select “Date and time”. Using keys ▲▼ you can adjust the chosen value. Upon reaching the maximum
value, e.g. in the 23rd hour, the counter starts again
from the beginning. Press ◄► to skip between
hour, minute, month, day and year. The date takes
account of the leap year. It is, however, important
to ensure that no invalid day-month combinations
are entered.
24
Figure 37: Sensitivity
Figure 36: FFT memory
Figure 38: Time and date
Additionally, clock inaccuracy can be corrected. This can be done using the setting
at “Cal.” in ppm (parts per million). The clock frequency can be increased with pos itive values and decreased with negative. The sign changes to minus at +254 ppm.
10.3. Shut-off Timer
The VM31 has a shut-off timer to help prolong the
battery operating life. To set the shut-off timer, open
the main menu by pressing F3, select “Device settings” and “Shut-off timer”. Press keys ▼▲ to select the timer duration from the options 1, 5, 15 and
60 minutes. To deactivate the timer select ('none').
The switch off timer starts to run after the last press
of a button. If a button is pressed the timer will
restart the count down for the set duration.
10.4. Battery Type
While non-rechargeable batteries have a cell voltage
of approx. 1.5 V, NiMH rechargeable batteries deliver around 1.2 V per cell. The discharge curves
are also different. The VM31 battery indicator can
be adjusted to both types. To select the battery,
open the main menu by pressing F3, select “Device
settings” and “Battery type”.
Within the sub-menu select “Battery type” (Figure
40) pressing ▼ selects between “Alkaline” (nonrechargeable, 1.5 V) or “NiMH” (rechargeable,
1.2 V).
If the battery power drops below 10 % the battery
indicator becomes red. Further measurements can
be taken until the power supply reaches 3 V in
keeping with the device specifications. At this point
the battery level indicator is completely empty and
the device switches itself off automatically.
10.5. Display Brightness
In the menu “Device settings”/ “Display brightness”,
press the keys ◄► to adjust the display settings according to your working environment. The main
purpose of reducing display brightness is to save
battery power. Current consumption increases by
approximately 20 % between the minimum and
maximum setting. The difference can be even
higher, depending on the display content.
10.6. Menu Language
Open the menu “Device settings” / “Menu language” to change the display language. The available languages depend on the firmware installed.
25
Figure 39: Shut-off timer
Figure 40: Battery type
Figure 41: Brightness
10.7. Default Settings
If you would like to reset your VM31 to factory set tings, open the menu “Device settings” / “Load defaults” . This will also delete the memory but will
not alter the transducer sensitivities.
11. Reset Key
If it occurs that the VM31 does not respond to the
press of any key, press the reset key to restart the
device. The reset key is reached with a thin object
through the aperture next to the type label (Figure
43).
Saved data and settings are not lost when the device
is reset.
12. Connection to a PC
The VM31 has a USB interface. The VM2x-USB cable (Figure 44) is connected to
the VM31 via its 8 pin connector. Switch the device off before connecting it to the
PC.
Connect the other end of the cable to a USB port on the computer and switch the
VM31 on again. If the device is being connected with a particular computer for the
first time, a driver installation will be necessary. The driver MMF_VCP.zip can be
found on our website: http://mmf.de/software_download.htm
Unpack and save both driver files in a directory on your computer.
When Windows requests details of the source of the device driver, this directory
should be entered.
26
Figure 44: USB cable VM2x-USB
Figure 43: Reset button
Figure 42: Default settings
The device driver is digitally signed and runs with Windows XP, Vista, 7 and 8.
13. Data Transfer to a PC
13.1. Opening the Excel File vm31.xlsm
The Excel macro file vm31.xlsm is provided to transfer, display and archive data
from the VM31. It can be downloaded from http://www.mmf.de/software_down-
load.htm. The file runs with all Excel versions starting from Excel 2007.
It transfers the stored data from the connected VM31 memory into Excel tables. Vi bration exposure A(8) or VDV(8) can be calculated from the human vibration
records and measuring reports can be generated. FFT data can also be transferred
and displayed graphically.
To work with the file you need to allow macro execution. Click the Office button,
then “Excel options”, “Trust center”, “Trust center settings” and “Macro settings”.
Either choose “Disable all macros with notification” or “Enable all macros”. With
the first option you will be asked for permission each time you open the file. With
the second option Excel will not ask you for permission again, but there is a poten tial risk of unwanted or dangerous macro codes being executed from other sources.
27
Figure 45: Macro settings in Excel 2010
13.2. Data Import to Excel
Open the worksheet “Import”. If previous measurement data appears in the table,
please save the file under another name and then click “Clear tables” to erase all
measurements from the tables. Connect the VM31 to a USB port on the PC and
switch it on. If not done before, install the device driver (section 12). Click “Import
measurements from VM31”. The device with its virtual COM port will be automatically detected. In rare cases detection may fail, due to other connected USB hard ware using virtual COM ports. It may be necessary to disconnect such hardware be fore data transfer.
The messages in the “Status” field inform you about import progress. Data import
may take between a few seconds and some minutes depending on the amount of
data. When the transfer is completed Excel will automatically sort the data into the
following worksheet columns: record number, date, time, comment, mode, filter and
the measurements of X/Y/Z and A. Columns B and C contain the combined values.
13.3. Calculation of Vibration Exposure A(8) and VDV(8)
Vibration exposure A(8), and alternatively, VDV(8), are both used for the risk assessment of human vibration. They can be calculated based on hand-arm (H/A) and
whole-body measurements (W/B). Use the check boxes in the left column of the
import worksheet to select the data to be included in the vibration exposure calcula tion. Alternatively, you may click “Select all”. After selecting the data, click the
button “Transfer selected data to daily exposure worksheets”. This will transfer the
relevant records to the worksheets. These worksheets are available for RMS based
hand-arm and whole-body measurements and VDV based whole-body measurements.
A message box will show you how many records have been transferred.
Select and open a worksheet according to the type of calculation you require “A(8)
RMS H-A”, “A(8) RMS W-B” or “Daily VDV W-B”.
Vibration exposure can be calculated for several persons and activities, i.e. partial
exposures. For this purpose there are two drop down menus for each record. The ten
cells “Person” and “Activity” above the table may be overwritten with your own
text. The changes you have made will be shown in the drop down menus the next
time you transfer data.
28
Figure 46: Excel import
Click “A(8) calculation” or, in the case of VDV, “Daily exposure calculation” to
calculate the vibration exposure (Figure 47). The result(s) will be compared with the
limits stated in the EU directive 2002/44/EC and are displayed in various colors:
black: below exposure action value
purple: between exposure action value and exposure limit
red: above exposure limit
During vibration exposure calculation a report is generated automatically. You can
find it in the worksheet “... Report”. It includes tables with the measured values and
the partial exposure values for each person and activity. Below you will find the vi bration exposure results for each person (Figure 48).
13.4. FFT Data Import to Excel
The FFT data stored on the VM31 can also be transferred to the Excel macro file.
Switch to the worksheet “FFT Import”. If previous FFT data is appears in the table,
please save the file under another name and click “Clear FFTs” to clear the table.
Then click “Import FFTs from VM31”.
The frequency steps along with the respective amplitudes of X/Y/Z are sorted into
table rows. You will see the date, time and comment for each record. Tick the check
boxes on the left hand side of each record to select which FFTs should be displayed
in the three diagrams above the table (Figure 49).
29
Figure 47: Daily exposure calculation in Excel
Figure 48: Example report (part)
14. Firmware Update
The device software (Firmware) can be updated via the
USB port. First of all, check whether a more up-to-date
version than the one currently installed is available. To
view the latest version visit our 'Software Download'
site.
http://www.mmf.de/software_download.htm
Here you will see the most recent firmware version
available. The version number is composed of three
digits for the hardware and three for the software (hhh.sss). Only the last three digits are relevant for the
firmware.
The version currently installed in your device is displayed on the start screen (Figure 50).
If a Firmware version with a higher number is available on the website, proceed as
follows:
1. Download the firmware file vm31.hex from the above named internet address.
2. Also download the program “Firmware Updater” from the above named internet
address and install it on your PC.
3. Connect the VM31 to the PC using the USB cable and switch it on so that Windows can detect it as a USB device and assign a COM port.
4. Start the “Firmware Updater”, then select the device type “VM31” and the virtual COM port assigned by the PC. If you are not sure which of the available
COM ports is correct, you can check in the Windows system control manager
located within the device manager.
30
Figure 49: FFT Import to Excel
Figure 50:
Firmware version
5. Click on “Load” in the “Firmware Updater” and enter the path to the file where
the downloaded firmware file vm31.hex is located.
6. In the VM31 “Device Settings” select the option “Firmware update” and confirm the warning and subsequent hint messages by pressing OK. By carrying out
this step the old firmware is deleted. The VM31 will then indicate that it awaits
new firmware data from the USB interface (Figure 52).
Figure 52: Firmware update
7. Click on “Send” in the “Firmware Updater”. Transfer of the Firmware data has
now begun. The transfer progress is displayed as a time bar on the PC and also
on the VM31. When the update is finished the VM31 will start up and the
“Firmware Updater” will close. Please do not interrupt the update process. Following transfer failures the update can be restarted at point 3.
Important: Before starting an update please ensure that the batteries are sufficiently
charged. Otherwise the update may fail and can only be restored by the manufacturer.
31
Figure 51: Firmware Updater
15. Calibration
The VM31 is supplied with a factory calibration. In this way it is assured that the in strument measures accurately if a calibrated transducer is connected and its sensitiv ity entered (see section 10.1). Month and year of the last calibration are shown on
the start screen (Figure 50).
The standard ISO 8041 lays down the requirements of electrical and mechanical cal ibration of human vibration meters.
Figure 53 shows the connections for calibrating the VM31 with electrical signals.
The signal generator needs to be connected via the shown R-C combination to the
inputs X/Y/Z and A. The 4.7 kΩ resistor serves as a sink for the IEPE constant currents. The 1000 µF capacitor keeps the resulting DC voltage drop away from the
generator. The electrolytic capacitor must be rated for at least 25 V. Please make
sure that the generator output can handle the resulting load of approx. 1 kΩ.
Plug for X/Y/Z: Binder 711 series, 4 pins, order no. 99-0079-100-04
Plug for A: Binder 711 series, 8 pins, order no. 99-0479-100-08
The maximum input voltage without overload indication is ± 1150 mV.
32
Figure 53: Connections for electrical calibration
GND
X
Y
Z
+
4k7
1000µ
Generator
GND
X
+
4k7
1000µ
GND
Y
+
4k7
1000µ
GND
Z
+
4k7
1000µ
GND
A
GND
A
16. Technical Data
Inputs 4 Low-power IEPE inputs, 1 mA / 17 V,
transducer sensitivity range 0.8 to 120 mV/ms
-2
TEDS support for template 25 to IEEE 1451.4
Display functions
Human vibration
General vibration
(acceleration /
velocity /
displacement)
Interval RMS
Vector sum
Maximum running RMS (MTVV)
Vibration dose value (VDV)
Crest factor (whole body only)
Running RMS
Maximum running RMS
Vector sum
Peak value
Maximum peak value
Measuring ranges
Acceleration
Velocity
Displacement
(zero-to-peak values)
Sensor with 1 mV/ms
-2
1100 m/s²
100 - 10 000 mm/s (1 kHz /1 Hz)
250 - 15 000 µm (5 Hz / 250 Hz)
Sensor with 10 mV/ms
-2
110 m/s²
10 - 1000 mm/s (1 kHz /1 Hz)
25 - 1500 µm (5 Hz / 250 Hz)
Display resolution
Acceleration
Velocity
Displacement
Sensor with 1 / 10 mV/ms
-2
0.01 m/s²
0.1 mm/s
1 µm
Sensor with 100 mV/ms
-2
0.001 m/s²
0.001 mm/s
0.1 µm
Linearity range > 75 dB (for < ± 6 % error)
Noise < 0,003 m/s²
Filters
Human vibration
Acceleration
Velocity
Displacement
Weighting filters Wb, Wc, Wd, Wh, Wj, Wk, Wm
Unweighted: 6.3 - 1259 Hz (hand-arm); 0.4 - 100 Hz (whole-body)
0.2 Hz – 1.5 kHz; 1 Hz – 1 kHz
1 Hz – 100 Hz; 2 Hz – 1 kHz; 10 Hz – 1 kHz
5 Hz: – 250 Hz
Frequency analysis 125 line FFT for X/Y/Z; Peak spectrum of acceleration
Frequency ranges: 3 - 240, 6 - 480, 12 - 960, 24 - 1920 Hz
Refresh rate: 0,5/s; Windowing: Hann
Data memory Flash; 10 000 measurements; 1000 FFTs; 100 log files of 32,000
records each
Display OLED, colored, 128×160 pixels
USB interface USB 2.0, full-speed, CDC mode, via cable VM2x-USB
Batteries 3 cells size AAA or Alkaline (LR03) or rechargeable NiMH
(HR03)
Battery oper. time 10 - 14 hours
Oper. temperature - 20 – 60 °C
Dimensions 125 mm x 65 mm x 27 mm (without connectors)
Weight 140 g (with batteries, without sensor)
33
Limited Warranty
Metra warrants for a period of
24 months
that its products will be free from defects in material or workmanship
and shall conform to the specifications current at the time of shipment.
The warranty period starts with the date of invoice.
The customer must provide the dated bill of sale as evidence.
The warranty period ends after 24 months.
Repairs do not extend the warranty period.
This limited warranty covers only defects which arise as a result
of normal use according to the instruction manual.
Metra’s responsibility under this warranty does not apply to any
improper or inadequate maintenance or modification
and operation outside the product’s specifications.
Shipment to Metra will be paid by the customer.
The repaired or replaced product will be sent back at Metra’s expense.
Declaration of Conformity
According to EMC Directive 2014/30/EC
Product: Triaxial Vibration Meter
Type: VM31 (from Ser. no. 160000)
It is hereby certified that the above mentioned product complies
with the demands pursuant to the following standards:
DIN EN 61326-1: 2013
DIN EN 61010-1: 2011
DIN 45669-1: 2010
The producer is responsible for this declaration
Metra Mess- und Frequenztechnik
in Radebeul e.K.
Meißner Str. 58, D-01445 Radebeul
declared by
Michael Weber
Radebeul, April 22, 2016
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