1.319 Level-Monitoring

The Level-Monitoring logical device monitors a level reading like a beacon level and raises several fault flags depending on the monitored level compared to some thresholds defined on the first device window page. Beside the level value itself the device also monitors the slope of this level, uses this to detect a falling level in critical situations quickly.

This device primarily is intended to monitor a beacon level and to make the decision for a site diversity switch. Its function is best explained by describing the parameter available on the first device window page:

• levelthreshold --- If the monitored level drops below this value, the device raises a "Threshold" fault. This fault by default is set to WARNING priority. It does not cause a site switch immediately but with the level below this threshold the device pays closer attention to changes of the level.
• leveldelay --- If the level is (constantly) below the threshold value for this time, the device raises the "Low level" fault. This fault may be configured to cause a site switch.
• slopethreshold --- While the level is below the threshold, the device also monitors the slope of the input signal. If there is a fast signal drop (negative slope below the given threshold) a "Slope" fault is raised. Please note that the threshold value must be entered as a negative value (e.g. -1.0 dB/sec) to achieve the desired behaviour. Due to the technical nature of a slope, the "Slope" fault will probably only be present for a single driver cycle.
• backupthreshold --- This second level threshold causes the "Backup" fault to be raised if the input signal drops below it. It works independently from the thresholds described above and is intended to be used as some sort of inhibit signal for a site switch: "do not switch to this antenna, the beacon signal is too bad here"

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- This page shows the operational parameters.
• --- The device info page.
• --- The faults page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

At the maintenance page of the device window there is one single configuration parameter which must be set to interconnect the Level-Monitoring device to its signal source:

Remarks

The Level-Monitoring device is not limited to the usage described above. By tweaking the parameters individual functions combined in this device may be used separately:

• By setting the level threshold to a high value, the device goes permanently to the "below threshold" mode. You may ignore the level threshold faults and use device as a simple slope limit detector. If you configure the slope threshold to a positive instead of a negative number as described above, the slope fault is raised when the input signal raises with a slope faster than the given limit.
• If you ignore the "Low level" and "Slope" faults, the device may be used as a simple 2-stage minimum level check device: If the level drops below the first threshold it raises a warning, if the level drops below a second (lower) threshold, a fault is raised.

Variables defined by this device driver