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6.5. Graphical Trend Display
The purpose of measuring vibration according to ISO 10816 and ISO 13373 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 measurements are taken at regular time intervals, from the same points and under the same
conditions.
To deliver the service staff on site a report about the periodic changes in vibration severity and consequently the previous history of the measurement point concerned,
the PCE-VM 25 provides a graphical trend display. The prerequisite for retrieving graphical trends is placing the sensor on the relevant VMID. The trend display is
obtained by pressing the F1 key (Figure 24).
The trend display only takes values from the data memory into account which belong to the VMID operation mode currently active. If the VMID operation mode is
changed (cf. Chapter 6.3.3), the previously saved data with a different operation mode will not be shown in the trend display.
Figure 24: Trend display
The vertical axis indicates the RMS of the vibration quantity and the horizontal axis indicates time. The K(t) values are represented by the vertical axis K(t). Both are
scaled to their respective maximum value. The time axis shows the interval between the first and last saved measurement. Below the diagram there is a red marker.
This can be moved horizontally to read the magnitude, using the◄► keys. The marker only skips forward to time points which already have a measurand. At each data
point the date and time of the measurement as well as the measured RMS or K(t) value are displayed. Above the diagram the text assigned to the measurement point is
displayed. In order to be able to display trends, the points are joined together by a line.
Press F3 to exit the trend display.
If only one or zero measurands for a selected measurement point can be located in the memory, the error message “Too few data for trending” will appear instead of
the trend graphic.
Note: The available PC software enables you to view the trends more conveniently, even without it being connected to the measuring point .
6.6. Viewing Saved Measurement Values
In addition to the graphical trend readings for current measurement points, saved measurement data can be viewed in text format. Open the main menu by pressing F3, then select
the sub-menu option “Meas. data Memory”. From within the submenu select “View meas. data memory”. The measurement data can be viewed in order of the VMID serial number
or the date it was saved. Select your preferred menu option using keys ▼▲ and press OK to confirm. The first data record will now be displayed. At the top, a consecutive number
and the number of the data record within the memory will also be shown. Below these, the measuring point serial number and its assigned text are also displayed. The RMS and
peak value are displayed underneath the date, time, display mode and filter type.
(Figure 25).
EN - 17
