MMF VM23 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: [email protected] Internet: www.MMF.de
Vibration Meter
VM23
Valid from firmware ver. xxx. 7

Published by:
Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K.
Meißner Str. 58
D-0 445 Radebeul
Tel. [phone]
Fax [phone]
Email [email protected]e
Internet www.MMF.de
Note: The latest version of this manual can be found at http://www.mmf.de/prod-
uct_literature.htm
Specification subject to change.
© 20 6 Manfred Weber Metra Mess- und Frequenztechnik in Radebeul e.K.
Full or partial reproduction subject to prior written approval.
Jan/ 2

Contents
. Purpose.................................................................................................................3
2. Function................................................................................................................3
2. . The Sensor.....................................................................................................3
2.2. The Measuring Instrument............................................................................4
3. The Measurement Procedure................................................................................4
4. The Batteries.........................................................................................................6
4. . Inserting the Batteries....................................................................................6
4.2. Switching On and Off....................................................................................7
4.3. Battery Display and Battery Type.................................................................7
4.4. Shut-off Timer...............................................................................................8
5. Preparation of Measuring Points...........................................................................9
5. . General Information on Measurement Point Choice......................................9
5.2. ISO 208 6- Recommendations....................................................................9
5.3. VMID Measurement Point..........................................................................
5.3. . How the VMID Measurement Point Functions....................................
5.3.2. Mounting the VMID Measurement Point.............................................
6. Measurement...................................................................................................... 2
6. . Measurement Value Display........................................................................ 2
6.2. Measurement Point Detection...................................................................... 2
6.2. . Reading the VMID Data with the VM23............................................. 2
6.2.2. Entering the Measurement Point Text.................................................. 3
6.2.3. Deleting Measurement Point Data....................................................... 4
6.3. Saving Measurands...................................................................................... 4
7. Viewing Saved Measurement Data..................................................................... 5
7. . Graphical Trend Display............................................................................. 5
7.2. Viewing Saved Measurement Values.......................................................... 6
7.3. Deleting all Measurement Data................................................................... 6
8. Measurement Evaluation.................................................................................... 6
9. Setting the Date and Time.................................................................................. 9
0. Calibration........................................................................................................20
. Sensor Check....................................................................................................22
2. Reset Key..........................................................................................................22
3. Connection to a PC...........................................................................................23
3. . Device Driver............................................................................................23
3.2. Firmware Update.......................................................................................23
4. Technical Data..................................................................................................26
Appendix: Warranty
Declaration of CE Conformity

2
Figure : VM23 with sensor

Thank you for choosing a Metra Vibration Measurement Instrument!
1. Purpose
The VM23 has been developed, particularly, for the measurement and monitoring of
vibrations on rotating machines. In addition is is a useful tool for machines which
have the purpose of generating vibration, like vibration conveyors, vibrating screens
and separators.
Such measurements help 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 guarantees.
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 VM23 measures and records vibration velocity, also known as vibration sever-
ity. Its specification corresponds to the ISO 2954 regulations and is suitable for,
among other things, the measurement of machine vibrations on machines with a
nominal speed at or above 20 min- , in accordance with ISO 08 6. Additionally
the VM23 can measure vibration displacement and main frequency.
The VM23 includes different band filters for acceptance measurements according to
various standards, like ISO 208 6 or ISO 8528.
An external piezoelectric accelerometer is used as the sensor, and is provided to-
gether with the instrument. The VM23 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 VM23 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
technology.
In the development of the VM23 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 Sensor
The VM23 operates with a piezoceramic shear accelerometer. Piezoelectric vibra-
tion transducers are characterized by high precision and resolution with great ro-
bustness. The accelerometer of the VM23 has an integrated electronic circuit for im-
pedance 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 VM23 supplies the IEPE Sensor with 2 mA
constant current. At the sensor output, a vibration acceleration proportional AC
voltage arises, which is amplified in the instrument to produce an optimum level.
The gain switch-over takes place automatically. The subsequent analog/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), RMS and peak-to-peak value calculation and fre-
quency analysis for main frequency detection, is carried out in the micro controller.
The micro controller also controls the graphic display, the USB communication and
the storing of measurements.
3. The Measurement Procedure
Measuring vibration velocity is a common procedure for assessing the running smooth-
ness of rotating machines. Vibration velocity, commonly known as vibration severity, is
a measurement of the energy expenditure of occurring vibrations. Vibrations are caused
by rotational imbalances, for example as a result of loose screws, bent parts, worn or
slack bearing clearance or dirt residues on fan blades. Often several factors have a mutu-
ally reinforcing effect. Besides rotary machines, the measurement procedure is also suit-
able for reciprocating 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 VM23 has additional frequency ranges from 2 to 00 Hz and 2 to 000 Hz.
The corresponding frequency response graphs can be viewed in Figure 3.
The displayed values of the vibration severity are true RMS or true peak-peak.
For reasons of conformity with older instruments the VM23 also measures equivalent
peak-peak which is calculated by multiplying RMS with 2√2.
Note: Equivalent peak-peak measurements are only accurate for sine-wave oscillation.
In spite of this limitation equivalent peak-peak may be advantageous if true peak-peak
readings are very fluctuating. Higher stability is achieved by averaging over 2 seconds.
4
Figure 2: Block Diagram
IEPE
supply
Progr.
amplifier
A
D
Micro
controller
Display
Memory
Keys
Sensor
ID
USB
Power
supply

These settings are made in the main menu under “Measuring mode”.
For machines with the purpose of generating vibration, like vibration conveyors, vi-
brating screens and separators the VM23 can display the main vibration frequency.
At such machines the magnitude is usually measured as displacement.
Note: Displacement amplitudes at higher frequencies are very small due to double
integration of the accelerometer signal. Above approx. 300 Hz only the last digit of
the display changes. Therefore the diagram in Figure 4 shows ripple at the upper
end. Displacement measurements at higher frequencies should be avoided if possi-
ble since they are inaccurate. The ranges 2 to 000 Hz and 0 to 000 Hz are only
provided for reasons of compliance with some standards demanding such limits.
5
Figure 3: Frequency Response for vibration velocity
1 10 100 1000 10000
0,001
0,010
0,100
1,000
10,000 v: 2-100Hz
v: 10-1000Hz
v: 2-1000Hz
Hz
mm/s
Figure 4: Frequency Response for vibration displacement
1 10 100 1000
0,001
0,010
0,100
1,000
10,000 d: 3-60Hz
d: 3-200Hz
d: 2-300Hz
d: 2-1000Hz
d: 10-1000Hz
Hz
mm

4. The Batteries
4.1. Inserting the Batteries
The VM23 is supplied by three alkaline standard cell type AAA (LR03) batteries.
NiMH batteries (HR03) may also be used. The minimum energy requirement of the
VM23 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 device will perform a new start once the
batteries have been changed. Following a 'new start' the date and time will need to
be newly set. Further settings as well as the saved measurands, are stored without
need of the batteries.
To insert the batteries, remove the two screws from the back cover of the device and
open the battery compartment (Figure 5). 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.
6
Figure 5: Battery Compartment

Please use your local collection point to dispose of batteries.
Batteries do not belong to the household waste.
4.2. S itching 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 6).
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 0) along with the memory capacity.
By pressing the ON-OFF button again the VM23 switches itself off. In addition, the
instrument has an automatic shut-off timer for saving the battery power (see cf.
Chapter 4.4).
4.3. Battery Display and Battery Type
In the upper left corner of the VM23 display there is a battery level indicator (Fig-
ure 7). When the green battery symbol is full, the battery is fully charged.
7
Figure 6: Start Screen
Figure 7: Battery indicator upper left Figure 8: Select battery type

While non-rechargeable batteries have a cell voltage of .5 V, NiMH rechargeable
batteries deliver only .2 V per cell. The VM23 battery indicator can be adjusted to
both voltages. To adjust the voltage remove the sensor from the VMID and press F2
to open the main menu. Here the battery type can be changed by pressing F to
scroll down to the menu option 'Instrument Settings' and then pressing OK. Within
the sub-menu select “Battery type” by following the same instructions as before
(Figure 8) and then by pressing F scroll between F “Alkaline” (non-rechargeable,
.5 V) or “NiMH Accu” (rechargeable, .2 V). Confirm your choice by pressing OK
and exit the menu by pressing F2 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 measure-
ments can be taken until the power supply reaches 2.8 V in keeping with the instru-
ment specifications. At this point the battery level indicator is completely empty and
the instrument switches itself off automatically.
If the VM23 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 in -
stead of the battery level indicator.
4.4. Shut-off Timer
The VM23 has a shut-off timer to help prolong the battery operating life. To set the
shut-off timer, remove the sensor from the VMID and press F2 to open the main
menu. From the main menu scroll down to the sub-menu option “Instrument Set-
tings” by pressing F and OK. Here the menu option “Shut-off timer” can be se-
lected by pressing F and the timer duration options of , 5, 5 and 60 minutes can
be selected, alternatively to deactivate the switch off timer select “none”. The auto-
matic switch off timer starts to run after the last press of a button. If a button is
pressed then the timer restarts and counts down again according to the duration se-
lected.
8
Figure 9: Shut down time