Thank you for choosing a Metra Vibration Measurement Instrument!
1. Purpose
The VM24 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
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 VM24 measures and records vibration acceleration, vibration velocity or vibra-
tion displacement. The VM24 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 10816.
An external piezoelectric accelerometer is used as the sensor, and is provided to-
gether with the instrument. The VM24 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 VM24 is equivalent to 'Level
1'. 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 VM24 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 VM24 operates with a piezo ceramic shear accelerometer. Piezoelectric vibra-
tion transducers are characterized by high precision and resolution with great ro-
bustness. The accelerometer of the VM24 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.
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