MMF VM25 User manual

Instruction Manual
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meissner Str. 58 - D- 1445 Radebeul
Tel. [phone] Fax [phone]
Email: [e-mail] Internet: www.MMF.de
Vibration Meter
VM25
Valid from Version 1. 9

Published by:
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meißner Str. 58
D-0 445 Radebeul
Tel. [phone]
Fax [phone]
Email [e-mail]
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.
© 20 2 Manfred Weber Metra Mess- und Frequenztechnik in Radebeul e.K.
Full or partial reproduction subject to prior written approval.
Feb/ 7

Contents
. Purpose..................................................................................................................3
2. Function.................................................................................................................3
2. . The Vibration Sensor......................................................................................3
2.2. The Measuring Instrument..............................................................................4
3. Measuring Ranges.................................................................................................4
3. . Measurable Vibration Quantities....................................................................4
3.2. Vibration Acceleration....................................................................................5
3.3. Vibration Velocity...........................................................................................5
3.4. Vibration Displacement..................................................................................7
3.5. Rolling Bearing Parameters K(t)....................................................................8
3.6. Rotational Speed............................................................................................9
3.7. Temperature....................................................................................................9
4. The Batteries..........................................................................................................9
4. . Inserting the Batteries.....................................................................................9
4.2. Switching On and Off................................................................................... 0
4.3. Battery Display and Battery Type.................................................................
4.4. Shut-off Timer.............................................................................................. 2
5. Preparation of Measuring Points.......................................................................... 2
5. . General Information on Measurement Point Choice..................................... 2
5.2. ISO 08 6- Recommendations................................................................... 2
5.3. VMID Measurement Point........................................................................... 4
5.3. . How the VMID Measurement Point Functions..................................... 4
5.3.2. Mounting the VMID Measurement Point.............................................. 4
6. Measurement....................................................................................................... 5
6. . Measurement Value Display......................................................................... 5
6.2. Selecting the Display Quantity..................................................................... 5
6.3. Measurement Point Detection....................................................................... 6
6.3. . Reading the VMID Data with the VM25.............................................. 6
6.3.2. Entering the Measurement Point Text................................................... 6
6.3.3. Editing and Deleting Measurement Point Data..................................... 8
6.4. Saving Measurands....................................................................................... 8
6.5. Graphical Trend Display............................................................................... 8
6.6. Viewing Saved Measurement Values............................................................ 9
6.7. Deleting Saved Measurement Data...............................................................20
6.8. K(t) Measurement.........................................................................................20
6.9. Frequency Analysis.......................................................................................23
6.9. . Settings.................................................................................................23
6.9.2. FFT Memory.........................................................................................24
6. 0. Rotation Speed Measurement.....................................................................25
6. . Temperature Measurement..........................................................................26
7. Measurement Evaluation with Standard Values...................................................27
8. Setting the Date and Time....................................................................................29
9. Calibration...........................................................................................................30
0. Sensor Check.....................................................................................................32
. Headphone Output.............................................................................................32
2. Reset Key...........................................................................................................33

3. Connection to a PC............................................................................................33
3. . Device Driver.............................................................................................33
3.2. VM2x Measurement Database....................................................................34
3.3. Export of FFT Data to a PC........................................................................35
3.4. Firmware Update........................................................................................36
4. Technical Data...................................................................................................38
Limited Warranty....................................................................................................40
2
Figure : VM25 with vibration sensor

Thank you for choosing a Metra Vibration Measurement Instrument!
1. Purpose
The VM25 has been developed, particularly, for the measurement and monitoring of
vibrations on rotating machines. The purpose of such measurements is to monitor
the condition of the machine in order to avoid unscheduled shut-down. Furthermore
vibration measurement is carried out prior to the distribution of new machinery and
subsequently to repair with a view to quality control and the issuing of product guar-
antees.
The basis for successful machine condition monitoring is the measurement of the vi-
bration severity over a longer period of time. Measurements are taken at regular in-
tervals of time and recorded.
The VM25 measures and records vibration acceleration, vibration velocity or vibra-
tion displacement. The VM25 specification complies with the ISO 2954 regulations
for machines that measure vibration velocity and is therefore suitable for measuring,
among other things, machine vibrations in accordance with ISO 08 6.
In addition to vibration quantities the VM25 also measures the temperature and the
rotation speed with contactless sensors.
An external piezoelectric accelerometer is used as the sensor, and is provided to-
gether with the instrument. The VM25 is fitted with an electronic measurement
point detector (VMID) which enables it to take routine measurements of a large
number of measurement points very effectively. A software package for transferring
the measurement data to a PC is also available from Metra.
In the common hierarchy of condition monitoring the VM25 is equivalent to 'Level
'. This represents the long term monitoring of parameters with low technical and
personnel requirements.
For fault detection ('Level 2'), as a further step, spectral diagnostic measurements are
taken, which require a large degree of expertise and sophisticated measurement tech-
nology.
In the development of the VM25 value was placed on simple operation and mainte-
nance requirements, which enable trained personnel to operate the instrument with-
out the need of being specially qualified.
2. Function
2.1. The Vibration Sensor
The VM25 operates with a piezo ceramic shear accelerometer. Piezoelectric vibra-
tion transducers are characterized by high precision and resolution with great robust-
ness. The accelerometer of the VM25 has an integrated electronic circuit for imped-
ance conversion in accordance with the IEPE standard. At the base of the sensor a
magnet has been integrated for mounting to the measurement point. In the center of
the magnet there is a contact point from which the identification number can be
read. The measurement point ID is saved in the available VMID measurement
points.
The coupling surface is protected by a metal cap which attaches to the sensors mag-
netic base.
3

2.2. The Measuring Instrument
Figure 2 shows the block diagram. The VM25 supplies the IEPE Sensor with 2 mA
constant current. At the sensor output, a vibration acceleration proportional AC volt-
age arises, which is amplified in the instrument to produce an optimum level. The
gain switch-over takes place automatically. The subsequent analogue/digital con-
verter is a Sigma-Delta converter with 24 bit resolution.
Further signal processing, such as filtering, integration (for calculating velocity and
displacement from acceleration) as well as the RMS and peak value rectification is
carried out in the micro controller. The micro controller also controls the graphic
display, the infrared thermometer, the rotation speed sensor, the USB communica-
tion and storing of measurements.
3. Measuring Ranges
3.1. Measurable Vibration uantities
The VM25 can display the vibration quantities acceleration, velocity and displace-
ment. Velocity and displacement are generated by single or double integration of the
sensor acceleration signal.
Furthermore, various frequency ranges can be selected.
The display rate adjusts itself according to the selected quantity in order to ensure
that the RMS does not fluctuate even at lower frequencies. The following table
shows the display rates.
4
Figure 2: Block Diagram
IEPE
supply
Progr.
amplifier
A
D
Display
Memory
Keys
Sensor
ID
Power
supply
USB
RPM
sensor
Infrared
thermometer
Micro
controller

Measurand Frequency Range Display Rate Sample Rate
Vibration acceleration 0,2 Hz – 0 kHz 5.6 s 23.438 kHz
Vibration acceleration 3 Hz – kHz .4 s 2.930 kHz
Vibration acceleration kHz – 0 kHz .4 s 23.438 kHz
Vibration velocity 2 Hz – kHz .4 s 2.930 kHz
Vibration velocity 0 Hz – kHz .4 s .7 9 kHz
Vibration displacement 5 Hz – 200 Hz 2.8 s 2.930 kHz
3.2. Vibration Acceleration
The VM25 has the following frequency ranges for vibration acceleration:
•0.2 Hz to 0 kHz: full frequency bandwidth of the accelerometer
•3 Hz to kHz: lower frequency acceleration
• kHz to 0 kHz: high frequency vibration only
In this way specific signal components can be measured whilst others are attenuated.
For example, when taking measurements on machines, at a frequency of kHz to
0 kHz predominantly the running noise of rolling bearings can be monitored,
whilst vibrational unbalances are attenuated.
3.3. Vibration Velocity
Measuring vibration velocity is a common procedure for assessing the running smooth-
ness of rotating machines. Vibration velocity, commonly known as vibration severity,
represents the energy expenditure of occurring vibrations. Vibrations are caused by rota-
tional unbalances, for example as a result of loose screws, bent parts, worn or slack bear-
ings or dirt residues on the fan blades. Often several factors have a mutually reinforcing
effect. Besides rotating machines, the measurement procedure is also suitable for recipro-
cating machines.
The specifications of vibration velocity measuring instruments are described in
ISO 2954. In the ISO 2954 a band filter for the vibration velocity of 0 to 000 Hz is de-
fined. The displayed value of the vibration severity is the true RMS.
5
Figure 3: Frequency response curves for acceleration
,1 1 1 1 1 1 1
, 1
, 1
,1
1
1 a: ,2Hz-1 kHz
a: 3Hz-1kHz
a: 1kHz-1 kHz
Hz
m /s ²

Besides the frequency range of 0 to 000 Hz, the VM25 has a further frequency
range for vibration severity measurements from 2 to 000 Hz. This is suitable for
measurements on slow running machines with a nominal speed of less than
20 min- and on reciprocating engines according to ISO 08 6-6.
The corresponding VM25 frequency response graph can be viewed in Figure 4.
Vibration velocity is formed through integration of the acceleration measured by the sen-
sor. The following formula applies to sinusoidal signals:
v=a
2Πf
It is evident that in the case of constant acceleration (a) the value of velocity (v) drops at
higher frequencies (f). As a consequence the measuring range limits of the velocity mea-
surements are frequency dependent. (Figure 5).The maximum velocity measurable
with the VM25 is around 000 mm/s (RMS). It yields a frequency independent
6
Figure 4: Frequency response curves for velocity
Figure 5: Amplitude range for velocity (RMS)
1 1 1 1 1
1
1
1
1
1
v: 2Hz – 3 Hz
v: 1 Hz – 1kHz
Integrator
Hz
mm/s
1 1 1 1 1
, 1
, 1
,1
1
1 v: 1 Hz – 1kHz
v: 2Hz – 1kHz
Hz
mm/s

modulation range of up to 40 Hz. At higher frequencies (RMS) the measuring range
limits for acceleration of around 240 m/s² take effect. In the attenuation range of the
low pass filter the modulation is further restricted.
3.4. Vibration Displacement
The vibration quantity most easily observed is displacement, also known as the de-
flection of the vibration. It is formed by double integration of the acceleration. In
comparison to velocity, the practically usable frequency range is even more re-
stricted. On the one hand it requires a high pass filter in order to attenuate low frequency
noise signals, which would otherwise appear amplified in the measurement values be-
cause of the double integration. On the other hand, frequencies in the range of less than
one hundred Hertz are so strongly dampened that an evaluable display value is no longer
recognizable.
Due to these restrictions, displacement measurements should only be applied where ac-
celeration or velocity is not capable of delivering the desired assessment.
The VM25 measures the vibration displacement from 5 to 200 Hz. The frequency re-
sponse diagram is shown in Figure 6. The curve ends at 200 Hz because even in the case
of a fully modulated sensor only single digit measurement values still occur.
The following formula applies to sinusoidal signals which have been formed through
double integration:
d=a
(2Πf)2
7
Figure 6: Frequency response curves for displacement
1 1 1 1
, 1
, 1
,1
1,
1 , d: 5Hz-2 Hz
Hz
mm

In the case of constant acceleration (a) it is visible that the displacement value (d) de-
creases quadratically with increasing frequency (f). As a consequence the measuring
range limits of displacement measurements are strongly frequency dependent. Figure 7
shows the measurement range limits depending on frequency.
The maximum displacement of the VM25 that can be measured is around 60 mm
(RMS). It yields a frequency independent modulation range of up to 0 Hz. At higher
frequencies the measuring range limits for acceleration of around 240 m/s² take effect.
3.5. Rolling Bearing Parameters K(t)
The rolling bearing parameter, also known as the diagnosis coefficient of Sturm
K(t), is an approved parameter for the condition analysis of rolling bearings, as de-
fined in the VDI 3832 (and other guidelines). It is formed by the RMS and peak
value of acceleration at a frequency range of to 0 kHz. The kHz high pass filter
ensures that the rolling bearing signal is not overlapped by the vibration of foreign
mechanical parts, such as imbalances.
The K(t) value relates the currently measured RMS and peak values to the RMS and
peak values at a starting point in time as follows:
K(t)= arms (0)⋅apk (0)
arms(t)⋅apk (t)
within this:
arms(0) RMS for the start point in time (reference point in time)
apk(0) maximum value (peak value) for start / reference point
arms(t) current RMS
apk(t) current maximum value (peak value)
The start or reference measurement is subsequent to first-time operation of the bear-
ing. Ideally after the elapse of a certain running-in time. At this point in time the
K(t) value is . Following ongoing wear and tear of the machine i.e. running dam-
8
Figure 7: Frequency response curves for displacement (RMS)
1 1 1 1
,1
1
1
1
1
Integratorkennlinie
d: 5Hz-2 Hz
Hz
mm

age, the K(t) decreases. During operation the K(t) value may also increase at a low
rate. In this way the condition of the rolling bearing can be classified:
K(t) Rolling Bearing Condition
> Improvement
.. 0.5 Good condition
0.5 .. 0.2 Damage progressive influences
0.2 .. 0.02 Advanced damage process
< 0.02 Damaged
Multiplication of the RMS and peak value indicates the acceleration over the course
of time as well as changes caused by shock, local damage (pitting), a general in-
crease in mechanical vibration due to distributed damage (worn race rings, corro-
sion, wear of rolling elements) or also insufficient lubrication.
The K(t) value only provides a statement about the condition of the bearing when
the trends are viewed. One single measurement does not enable a diagnostic state-
ment to be made.
The K(t) value is strongly dependent on the rotational speed. It is therefore impor-
tant to ensure that the rotational speed is the same, when viewing trends.
3.6. Rotational Speed
Alongside vibration the VM25 measures the rotational speed by means of an inbuilt
contactless optical sensor (Figure 34 on page 25). To enable this, the instrument
needs to be aligned with the rotating part, for which a laser pointer can be used to
help with the positioning.
Notice: Please do not cover the sensor apertures on the back of the instrument with
your fingers during measurement.
3.7. Temperature
The VM25 has an inbuilt infrared thermometer for taking contactless temperature mea-
surements (Figure 34 on page 25).
4. The Batteries
4.1. Inserting the Batteries
The VM25 is supplied by three alkaline standard cell type AAA (LR03) batteries.
NiMH batteries (HR03) may also be used. The minimum energy requirement of the
VM25 enables maximum utilization of the batteries.
Attention: Please switch the instrument off before changing the batteries. When
switched off, the contents of the memory are stored for a few minutes, without need
of the batteries, and the internal clock continues to run. If the batteries are removed
when the instrument is switched on or if they remain in the instrument until the bat-
teries have been completely discharged, the date and time will need to be reset. Fur-
ther settings as well as the saved measurands, are stored without need of the batter-
ies.
9

To insert the batteries, remove the two screws from the back cover of the device and
open the battery compartment (Figure 8). 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 instrument, and take out the batteries if the instru-
ment will not be used for a long period of time. Otherwise leaking battery acid
may cause severe damage to the instrument.
Please use your local collection point to dispose of batteries.
Batteries do not belong to the household waste.
4.2. Switching On and Off
The instrument is switched on by a short press of the ON-OFF button. A start screen
will be shown on the display for 3 seconds. (Figure 9).
0
Figure 8: Battery Compartment
Figure 9: Start screen

This displays the hardware version number (the 3 digits before the point) and the
software version number (the 3 digits after the point) followed by the serial number
corresponding to the type label. The month and year of the last calibration are dis-
played (cf. Section 9) along with the memory capacity.
By pressing the ON-OFF button again the VM25 switches itself off. In addition, the
instrument has an automatic shut-off timer for saving the battery power (cf. Chapter
4.4).
4.3. Battery Display and Battery Type
In the upper left corner of the VM25 display there is a battery level indicator ( 0).
When the green battery symbol is full, the battery is fully charged.
While non-rechargeable batteries have a cell voltage of .5 V, NiMH rechargeable
batteries deliver only .2 V per cell. The VM25 battery indicator can be adjusted to
both voltages. To adjust the voltage, open the main menu by pressing F3 and scroll
through the menu options by repeatedly pressing the ▼ button until you reach 'In-
strument Settings', then press OK.
Within the sub-menu select “Battery type” (Figure ) by following the same in-
structions as before and then by pressing▼ select between “Alkaline” (non-
rechargeable, .5 V) or “NiMH accu” (rechargeable, .2 V). Confirm your choice by
pressing OK and exit the menu by pressing F3 repeatedly.
If the power supply drops below 3.3 V when using alkaline batteries or below 3 V
with rechargeable batteries, the battery indicator becomes red. Further measurements
can be taken until the power supply reaches 2.8 V in keeping with the instrument
specifications. At this point the battery level indicator is completely empty and the
instrument switches itself off automatically.
If the VM25 is connected to a USB port, it will be supplied by the USB voltage in
order to spare the batteries. In this case, “external” is displayed on the screen instead
of the battery level indicator.
Figure 0: Battery indica-
tor upper left
Figure : Select battery type

4.4. Shut-off Timer
The VM25 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. Scroll down into the sub-menu
'Instrument Settings' by pressing▼and OK, and within this sub-menu select the
menu option “Shut off Timer”. Press keys ▼▲ to select the timer duration from the
options , 5, 5 and 60 minutes or to deactivate the timer select ('none'). The switch
off timer starts to run after the last press of a button. If any button is pressed then
the timer restarts and counts down again according to the duration selected.
5. Preparation of Measuring Points
5.1. General Information on Measurement Point Choice
When monitoring machines it is important to take measurements under the same op-
erating conditions, at the same measurement point. Choosing the suitable measure-
ment point is therefore decisive.
Where possible, qualified staff experienced in machine monitoring should be called
upon.
It is generally advisable to record machine vibrations near to their source. This helps
to reduce distortion of the measuring signal to a minimum when it is being carried
through transmission parts. Suitable measurement points include rigid machine com-
ponents such as bearing housings or gearboxes.
Light or mechanically flexible machine components such as cladding and casing are
unsuitable for the measurement of vibrations.
5.2. ISO 10816-1 Recommendations
The standard ISO 08 6- recommends bearing housings or their immediate sur-
roundings as preferred measuring location points for the measurement of machine
vibrations (Figures 3, 4, 5 and 6).
For the purpose of monitoring a machine it is normally sufficient to take measure-
ments in only one direction, either vertically or horizontally.
On machines with horizontal shafts and rigid foundations the largest vibration am-
plitudes occur horizontally. With flexible foundations, strong vertical components
also arise.
For the purpose of acceptance tests, measurement values are to be taken from all
bearing point locations at the center of the bearing and in all three directions (verti-
cal, horizontal and axial).
2
Figure 2: Shut-off time

The following illustrations give a few examples of suitable measurement point loca-
tions..
The Standard ISO 3373- also gives recommendations for measurement points on
various machine type.
Figure 3: Measuring points on vertical
bearings
Figure 4: Measuring points on flange
bearings
Figure 5: Measuring points on electric
motors
Figure 6: Measuring points on ma-
chines with vertical rotors
3
X
Y
Z
X
Y
Z
Z1 Z2
X2
Y1 Y2
X1
Z
X1 Y1
X2 Y2
X3
X4
Y3
Y4

5.3. VMID Measurement Point
5.3.1. How the VMID Measurement Point Functions
The VM25 is equipped with an electronic measuring point detector. Metra offers a
type VMID measurement point, which is made of magnetic stainless steel and has an
inbuilt memory with an individual serial number (Figure 7).
The serial number stored inside the measurement point is a unique 6-digit hexadec-
imal number, e.g. “000000FBC52B”.
Each measurand can be easily and reliably allocated to a specific measuring point.
To read the serial number, contact is made through the sensor's magnetic base.
The maximum permissible operating temperature for the VMID is 80 °C.
5.3.2. Mounting the VMID Measurement Point
A VMID measurement point is mounted onto the machine using two component
epoxy adhesive. For an accurate vibration transmission, Metra recommends the fol-
lowing adhesive:
•LOCTITE Hysol 3430 without filler for even surfaces
•LOCTITE Hysol 3450 with filler for uneven surfaces
Before applying the adhesive ensure that all residues of grease have been thoroughly
removed from both contact surfaces. The two component adhesive can be applied
directly onto the chosen surface. The adhesive takes 5 minutes to harden and after
5 minutes the first measurement can be taken.
For protection against dust and humidity according to IP67 please put the supplied
protective plastic cap on the VMID measurement points when no measurements are
taken.
4
Figure 7: VMID Measuring point

6. Measurement
6.1. Measurement Value Display
In the top margin of the screen (Figure 8) the battery power is displayed. Next to
this the date and time are also indicated..
Below the measurand (v: 0 Hz- kHz RMS) the currently measured value.
The display “No Point ID” indicates that a measurement point number has not been
identified.
Note: The decimal point may appear in one of two positions, dependent on the mea-
surand. This is due to the automatic gain switch-over. In this way smaller measur-
ands with high resolutions are sure to be detected
6.2. Selecting the Display uantity
With keys ◄► you can select from among the six available operation modes:
•Vibration velocity 0 Hz – kHz
•Vibration velocity 2 Hz – kHz
•Vibration acceleration 0.2 Hz – 0 kHz
•Vibration acceleration 3 Hz – kHz
•Vibration acceleration kHz – 0 kHz
•Vibration displacement 5 Hz – 200 Hz
•K(t) value for rolling bearing monitoring
•Rotational speed and temperature
By pressing F2 you can switch between RMS and peak value for the acceleration.
velocity and displacement.
The RMS is the so-called “true” root mean square value.
The peak value, also known as crest or maximum value, is the highest vibration
value since the last displayed value.
The crest factor, is the relation between crest value and RMS. It is used to describe
the curve form. For a sinusoidal signal it amounts to √2 = ,4 . The more impulsive
the signal, the higher the crest factor.
Note: When saving measurement values (chapter 6.4) the RMS and peak value are
always saved both irrespective of the currently selected setting.
5
Figure 8: Measurement display

If the sensor locates a VMID measuring point which is already saved in the VM25
memory, in order to prevent unintentional switch-over, a warning signal will be dis-
played when the measurand changes (Figure 9). By pressing OK the measuring
range can still be changed. The warning signal will not appear again until the next
measuring point is detected .
6.3. Measurement Point Detection
6.3.1. Reading the VMID Data with the VM25
The VMID measurement points are designed, so that the magnetic sensor base cen-
ters itself. To avoid mechanical shock do not let the sensor snap onto the measure-
ment point, instead, roll it slowly over the edge. To improve the vibration transmis-
sion the measuring point can be lightly lubricated.
As soon as the Sensor base comes into contact with the measurement point, the
VM25 displays the measurement point number (Point ID) (Figure 20).
6.3.2. Entering the Measurement Point Text
If a measurement point has not yet been assigned a text, press the▼ key to reach the
text edit menu (Figures 20 and 2 ).
A space of two rows consisting of 0 characters each is assigned for each measure-
ment point text. The text is entered using keys ▼▲. By pressing keys ◄► you can
change the character position. Both capital letters (A to Z) and numbers (0 to 9) are
available. To move down to the next row press F . By pressing F again and using
keys▼▲ the operation mode can be selected.
6
Figure 20: Newly recognized VMID
Figure 9: Warning at mode change

By pressing OK the entries will be saved and the menu exited.
Press F3 to exit the menu without saving the changes.
Note: More conveniently, the measurement point texts can also be entered using the
available computer software.
Once you have assigned the VMID serial number a text, the VM25 will display the
text continually, as soon as the sensor makes contact with the measuring point (Fig-
ure 22).
Aside from this, the VM25 reverts automatically to the saved operation mode. In
this way it is ensured that measurements are always taken with the correct settings.
Note: Changing the measuring point data also effects the display of saved measur-
ands (cf. Chapters 6.5 and 6.6). The current saved text of the respective VMID serial
number is always displayed in the measurement data. Changing the operating mode
of a measuring point only affects measurands saved subsequently and does not have
any effect on the measurands that have already been saved in the memory.
The measurement point data is saved in the instrument. If several instruments are
used at the same measurement point location, the measurement point data will need
to be saved within each instrument. The available PC software enables the conve-
nient management of measurement points.
7
Figure 2 : Entering ID text
Figure 22: ID text display

6.3.3. Editing and Deleting Measurement Point Data
Open the main menu by pressing F3 and select the sub-menu “Point ID memory” by
using keys ▼▲.
Within the menu option “Edit Point ID”, as previously explained in section 6.3.2,
the measurement point texts and the operating mode allocated to the measuring
point can be changed. In the sub menu “Edit Point ID” press or hold down▼▲, un-
til the text you wish to edit is displayed and then press OK to edit.
Within the menu option “Erase Point ID”, measurement point data records, each
consisting of a VMID serial number, text and operational mode, can be deleted one
by one. In the subsequent menu “Erase Point ID”, press or hold down ▼▲, until
the record you wish to delete is shown, then press OK and confirm the warning by
pressing OK again(Figure 23).
In the same way, the entire measurement point data can be deleted as a whole by se-
lecting “Erase all Point IDs” in the “ID Menu”. The VM25 memory can store data
for a maximum of 600 measurement points.
Note: Deleting measurement point data effects the display of saved measurements.
(chapter 6.6). Instead of the measurement point serial number and the measurement
point text being shown, “none” is displayed. The measurement point data records
can always be newly generated, as described in 6.3.2.
6.4. Saving Measurands
Pressing the ▼ key saves the currently displayed measurand. Independently of
whether RMS, peak or crest factor display has been selected, the VM25 always
saves the RMS and peak value. Furthermore the respective measurement point num-
ber (if known), the chosen display mode and the date and time are also saved.
Note: If the sensor locates a measurement point which has not yet been assigned a
text or operational mode (cf. Chapter 6.3.3), use the ▼ key to enter the text.
6.5. Graphical Trend Display
The purpose of measuring vibration according to ISO 08 6 and ISO 3373 is as
follows; To make assessments concerning the operating condition of a machine
based on changes in its vibration behavior. To achieve this it is imperative, that mea-
surements are taken at regular time intervals, from the same points and under the
same conditions.
8
Figure 23: Deleting an ID record