Rockwell Automation T8082 Trusted Toolset Suite - Manual (Page 28)

Trusted
TM
Toolset Suite T8082
Issue 14 Feb 10 PD-T8082 28
When the correct channel and force states have been entered, the user must select the OK button.
This will return the user to the Template Creation window which permits the newly created template to
be saved. The filename must not include any spaces. Underscores are recommended.
2.3.10. Module System Information Templates
The typical entries for this template, include; NLthresh, IMBTO, WDOGTO, PWRFAILTO, and
BYPASSTO. The syntax and function of each entry is defined below.
nlthresh = < group1 >, < group2 >,< group3 >,< group4 > [,< group5 >]
nlthresh (‘no-load threshold’) is a template that is used on output modules. It sets the current per slice
(in milliamps) below which an output will signal state 3 (no load), and each of the parameters sets the
threshold for an entire power group of eight digital outputs. Without this template, the defaults are
10mA, i.e. at least 30mA is required for the load to be recognised.
Outputs do not share current evenly across the three TMR slices and there may be a significant
difference between slices. As an example, the 8451 output module has a minimum on state load
current of 50 mA per channel. With a load of 51mA, the load may be spread across the slices as
follows:
Channel 1 Slice A 26mA
Channel 1 Slice B 16mA
Channel 1 Slice C 9mA
Whilst the channel total is greater than the nominal minimum, slice C is below the default no-load
threshold (10mA) and would therefore signal a no-load state whilst the other two slices will record an
acceptable load. This causes a discrepancy alarm. In earlier firmware versions this may lead to a
module shutdown.
It is recommended to group comparatively high and low power loads on different power groups. This
prevents potential noise from a higher powered output affecting the lower powered signals. The
following no-load threshold settings are recommended for each group:
25 to 80 mA nlthresh = 5
80 to 150mA nlthresh = 10
150 to 300mA nlthresh = 15
300mA to limit nlthresh = 20
As an example, if groups 1 and 2 (channels 1 to 16) are approximately 100mA per channel and the
rest are 50mA per channel, the no-load thresholds should be set as:
nlthresh = 10,10,5,5,5
Output modules such as the 8471 (120Vdc) only have 4 output groups and the template is written, for
example, as:
nlthresh = 5, 5, 5, 5
Whilst some output modules have a minimum on state load current of 20 or 25 mA per channel, it is
still recommended to use the nlthresh template for these modules.
For the 8473, it is recommended to set nlthresh = 20, 20 because it will not accurately detect the no-
load condition below this value.