Operating functions via HART
7.21 Diagnostic functions
SITRANS P300 with HART communication
7-30
Operating Instructions, 06/2005, A5E00359579-02
See also
Overview of simulation (Page 7-32)
7.21.5
Limit modules
7.21.5.1 Overview of limit modules
Description
The diagnostic functions of this device provide you with the option of monitoring measured
values in limits that can be configured. When the limits are violated, the device warns you via
HART communication or reports an analog fault current to a higher-level recipient.
7.21.5.2 Monitoring of current saturation
Description
You can use a simple limit module to monitor the current output in the saturation range. This
module is configured and activated via HART communication. For HART communication,
use a HART Communicator or PC software such as SIMATIC PDM. You need to configure
two time periods. The first time period specifies how long the current output is allowed to be
in saturation (response time) before an interrupt is triggered and the device outputs its set
fault current. The second time period (stop time) specifies the duration of the interrupt.
In the first example, the response time starts at time t
1
, when the current reaches the
programmed saturation limit for the first time. At t
2
the response time ends and the stop time
begins. The interrupt is revoked immediately as soon as the programmed stop time has
passed (t
3
) and the current has gone below the saturation limit again.
In the second example, the duration of the current saturation is shorter than the response
time (t
1
, t
2
). In that case, the device does not go into "fault current" state.
In the third example, the current only exceeds the lower saturation limit for a short time. The
fault current is not switched off until after the end of the stop time (t
3
).
