How can I avoid taking measurements when the monitored equipment is not active?

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How can I avoid taking measurements when the monitored equipment is not active?

For software versions up to 1.6.3

You can set a threshold level for the Vibration Sensor to avoid the creating of useless data. The threshold can be set in the ‘Vibration Download’ section.

 

NOTE: the set threshold level does not apply for manually recorded measurements with the REC button.

 

 

After a measurement is completed by the sensor, a few samples (‘Prefetch’ number in the figure above) will be downloaded from the sensor and the RMS value of these samples will be calculated. When the measured RMS is higher than the threshold, the full measurement is processed and stored in the OPC database. Otherwise the sample measurement is dropped.

 

 

For software versions from 1.6.3

You can set a threshold level for the Vibration Sensors, the Piezoelectric Accelerometers and the Current Clamps to avoid the creating of useless data. The threshold can be set in the ‘Download Filter’ section.

 

NOTE: the set threshold level does not apply for manually recorded measurements with the REC button.

 

 

The histogram graph (see the figure above) shows the peak power measured in the sensor over time. The graph shows the peak power levels of the latest 50 measurements as a blue bar on a logarithmic scale with the bar of the newest measurement on the left and the bar of the oldest on the right. Each blue bar represents a reduced but complete pre-download of a historical measurement (previous data capture) over the full measurement period. This contrasts with the old threshold version where only the first “prefetch” measuring samples were downloaded for the calculation of a rough RMS value that was then compared to the set threshold level (in “g” units). By using this limited number of samples, impacts recorded later in the time series could be missed.

 

Threshold:

The red line in the histogram graph represents the set threshold level. If the blue bar level is above the threshold level, the complete measurement will be downloaded, and a green indication will be shown at the top of the graph.

 

  • Setting the threshold to “none” (default setting): the complete measurement will always be downloaded, even if the equipment is idle (the graph will show a full green line at the top).

 

 

  • Setting the threshold to “30%” shows that in this example the last 50 measurements and all future measurements will still be downloaded completely (the graph will show a full green line at the top).

 

 

  • Setting the threshold to “60%” shows how the last 50 measurements would have been downloaded for this example case (the graph will show green dots at the top for the downloaded measurements). The threshold level is now set accurately for future measurements.

 

 

Remark: if there are no measurements available yet, it is difficult to set the correct threshold level. In this case, it is recommended to enable the automatic measurements, to set the desired capture interval and to leave the threshold set to “none”. Wait for enough measurements to be downloaded and fill the histogram graph before setting the threshold level.

 

Remark: to conserve battery power, it is important to set the threshold level to something higher than “none” to prevent full downloads when the DUT is not active. The result is that the battery lifetime may be extended since less data must be transmitted.

 

Number of retries:

The “Retry” setting in the “Download Filter” section represents the number of extra capture attempts after the set measurement interval (if the threshold level is not exceeded yet). For example, if the measurement interval is set to 30 minutes and the number of retries to “5x”, a first measurement will be acquired after the set 30 minutes. If the peak power bar level of that acquired measurement is below the threshold level, extra capture attempts will be performed every 6 minutes (5 within each measurement interval period) until one of the measurements has a power level above the set threshold level. That complete measurement will then be downloaded. After the complete download, a new capture attempt will only be performed after the set measurement interval of 30 minutes has elapsed.

 

 

  • If the capture mode is set to “Peak”, the measurement will always be downloaded at the end of the set measurement interval (if above threshold level). The sensor is measuring continuously but only saves the measurement with the highest recorded peak power during the set time interval (for example a time series triggered by an impact). This saved measurement will then be downloaded at the end of the measurement interval. You thus receive the “smart” event-triggered sensor data. Setting the number of retries higher than “1x” will only have value in some rare cases in this capture mode like for example in the case of a bad wireless connection.

 

 

 

  • If the capture mode is set to “Instant”, the measurement is acquired and downloaded at the end of the set measurement interval (if above threshold level). You thus receive the “unsmart” purely time-based sensor data. If the number of retries is set to more than “1x”, the sensor will extend the measurement interval period with several retries (if the threshold level has not been exceeded yet) for acquiring for example a non-idle equipment measurement right after the interval period. If all retries are below the threshold level, the measurement interval period will be extended with more retries. If one of the retries is above the threshold level, that complete measurement will be downloaded. After the succeeded download, the next measurement attempt will only be started after the set measurement interval period has elapsed. The measurement scheduler thus uses the latest download as a reference point. The retry function allows us to acquire more non-idle measurements in case a machine is working intermittently.

 

 

 

Remark: “Peak” mode is only available for the cable powered sensors and not for the battery-powered sensors. For battery-powered sensors “Instant” is the default capture mode and therefore the capture mode selection box is not shown in the Sensor Dashboard.

 

Remark: using the retry function will off course consume more battery power than only taking 1 measurement per measurement interval, but battery consumption will be less than in the case of a short measurement interval where the measurements will always be downloaded idle or not.