Analog electronic modules
15.9 Dynamic reference temperature for the 4 AI TC High Feature electronic module
ET 200pro distributed I/O system
Operating Instructions, 03/2013, A5E00335544-08
433
15.9
Dynamic reference temperature for the 4 AI TC High Feature
electronic module
Properties
You can use the "Dynamic reference temperature" compensation type to measure the
reference junction temperature at the measuring point via the 4 AI RTD High Feature
electronic module or another station's external module. This involves transferring the
reference junction temperature to the 4 AI TC High Feature electronic module using SFB 53
"WRREC" via data record DS2.
Requirements
●
SFB 53 "WRREC" standard function block
●
User program (see example below)
Programming
Please note the following information regarding the user program:
●
The permissible value range for the reference junction temperature with standard
resolution corresponds to the Pt100 climatic temperature range for platinum RTDs, and
can be seen in the table titled
"Reference temperature" parameter for 4 AI TC High
Feature
in the section titled Parameter overview for analog electronic modules
(Page 419).
●
If a reference junction temperature outside the permissible value range is received in data
record DS2, a "Reference channel error" diagnostic interrupt is reported, assuming the
"Group diagnostics" parameter is enabled.
●
When the 4 AI TC High Feature electronic module starts up, all the inputs report an
overflow (32767). Once a compensation value has been received via data record DS2,
the electronic module starts to read the TC inputs and report the correct data. If the
electronic module does not receive any DS2 data within 5 minutes of starting up, a
"Reference channel error" diagnostic interrupt is reported, assuming the "Group
diagnostics" parameter is enabled.
●
The 4 AI TC High Feature electronic module features time monitoring (watchdog) set to
5 minutes, which is reset when a new compensation value is received via DS2. If the
electronic module does not receive any DS2 data within the 5 minutes of time monitoring
during normal operation, a "Reference channel error" diagnostic interrupt is reported,
assuming the "Group diagnostics" parameter is enabled.
●
If ET 200pro modules or other modules are being used to measure the reference junction
temperature, the RTD module parameters for the output structure and measuring
accuracy in DS2 must be represented by bytes 0 and 1. This can be seen in the "Data
record DS2 structure" figure below.
