Using XRatel Server Config

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       User Defined Probes Configuration

User Defined Probes are derived from ordinary SNMP or WMI variables, in most cases, implementing special calculations

to obtain performance indicators based on raw data.

User Defined Tag

There are five columns in the Probe Viewer:

Enable: Indicates if the Probe is active to server scan.

History: Add this Probe into XRatel Historian Service.

Device: Show the device which the probe is taking information from.

Probe Name: Name that will be used by the server to publish this variable.

Probe Description: An explain text for the Probe.

To manually add a User Defined Probe, you have to use the User Defined Probe button on the top toolbar. Then the User Defined Probe Wizard will open.

The User Tag Properties Dialog

You can customize the following item settings:
 

Probe Name: The name of the Probe.

Description: A textual description of the displayed value of the Probe.

1st Order Filter: Check to create an additional Probe (with "_Filtered" in the name) that applies a low pass filter in this item. This is only available for numerical variables.

Alarm setting is explained in Probes Settings.

In Next Screen the Expression Wizard will open. In the first step, define the expression using variables, in example you see the utilization formula:

utilization = ( ( 8 * ( delta(a) + delta(b) ) ) * c ) * 100

Expression Wizard

You can use up to eight variables to construct your own expression. Note that latin characters are not allowed to variable names.

It is possible to use the four basic operations - addition( + ), subtraction( - ), multiplication( * ) and division( / ) - and the delta function. This function calculate the delta of the specified variable:

delta(x) - calculate the difference between the current x value and the last saved value.

You can group expression parts using parentheses, simplifying the human reading and changing the formula interpretation:
a + b / c is different from (a + b) / c.

During expression edit, a validator will be executed below the expression box. If "The expression is invalid" text is show, an error was found and the formula needs to be revised.

Calculation Expression Wizard

Then, on third step, define the correspondent Raw Probes for each variable. Note that each variable is associated with a SNMP OID or a WMI Path, so if device MIB Tree or WMI Class change, all User Defined Probes must be checked for changes too.

You can search for a Probes in Probe List in the right of the dialog. This list is loaded from Raw Probe List, so it's recommended that you scan the device for Raw Probes before creating/editing User Defined Probes.
 

To simplify the search task, you can use the Look for filter at top of the Probe List.

To change the Raw Probe of a variable, drag a new probe to it.

User Defined Resume

On final step, you can see a resume with choose options will be showed. To finish this Wizard and save the new expression, click on the Finish button.  If you want to discard all changes, just click the Cancel button to close the dialog.