Micromod MOD: 1750N Output holder for MOD 30ML - Manual (Page 19)

Output Holder Instructions
CONFIGURATION
1. The compound uses an AIN (Built-in Analog Input) block configured as current input (4-
20mA) and a VCI block for ranging it to 0-100 engineering units linear. It also has a built-
in AOUT block. You can substitute different type of input or module, conditioning and
analog output blocks
2. The compound also has preconfigured PID, Display and Tuning List blocks, which you
can substitute with your existing blocks in your database.
3. The compound uses a built-in input (RETURN) and a VCI conditioning (RETURNF1)
blocks for reading the feedback from the output holder. This is the feedback of the output
value from the output holder sent to the field. This value is tied to the output track input
(OPTI) of the PID block so that the PID block tracks this value upon start up. This is how
a bump less transfer of output value is achieved. If you do not need bumpless transfer of
output, you can optionally remove these two blocks.
4. The AOUT block is configured as shown below for Restart/Failsafe conditions:
Figure 4 .5. AOUT / AOM block configuration
The Restart output is configured as Preset with a value of –25. The reason for this is
when a faulty controller is replaced with a new or a repaired one, a momentary zero
output from the controller at startup will be seen as a valid input by the output holder and
it will switch to zero values. To avoid this a momentary faulty value (negative 25) is
introduced at the startup and then the PID block’s output will override this value.
5. The compound uses a Digital input block (DIM - SENSE) and a digital conditioning block
(DI – SENSEF) to sense the presence of the output holder. This discrete signal along
4 -5