Instruction Manual

i.LON 100 Internet Server Programmer’s Reference 6-9

Property Description

This property applies to scalar data points only. Specify the

change in value required for an entry to the log to be made. For

example, if this property is set to 30.0, the value of the data

point being monitored must change by at least 30.0 during an

update for the change to be recorded by the Data Logger. All

updates are logged if this value is 0.0, or not defined.

This property has minimum and maximum floating point values

of +/-3.402823466e+038.

NOTE: If the format type used by the data point being

monitored is SNVT_temp_p#US or SNVT_temp#US, then the

value of this property returned by the DataLoggerGet function

will be displayed using the SNVT_temp_f#US_diff format type.

This rule applies to all formats that use the #US specifier.

The poll rate for the Data Logger can be between 0 and

214,748,364.0 seconds. The Data Logger will check for updates

to the data point at this interval. Echelon recommends that you

set this to a value greater than or equal to the value specified for

the <UCPTlogMinDeltaTime> property if you do not want to poll

data before updates to the log are possible.

If you use the default poll rate of 0 seconds, the Data Logger will

record each updates to the data points it is monitoring into the

log, assuming that the time period defined by the

<UCPTlogMinDeltaTime> property has elapsed and the change

in value specified by the <UCPTlogMinDeltaValue> property

has been met.

You should note that other i.LON 100 applications may cause

the Data Server to poll this data point’s value as well. The poll

rate specified by these applications should be compatible with

each other. For example, if an Alarm Generator is polling a data

point every 15 seconds, and the Data Logger is polling that data

point every 10 seconds, then the Data Server will have to poll

the value of the data point every five seconds to ensure that each

application gets a current value for each poll.

It is important to note this as you set poll rates for various

applications, as you may end up causing more polls than is

efficient on your network. For example, if an Alarm Generator is

polling a data point every 9 seconds and a Data Logger is polling

a data point every 10 seconds, the Data Server would have to

poll the data point every second to ensure that each application

polls for a current value. This may create a significant amount of

undesrired traffic.