Siemens SENTRON PAC4200, Руководство пользователя, Страница: 41 / 252

Description
3.8 Limit values
SENTRON PAC4200
Manual, 09/2008, A5E02316180B-01
41
Combination of the limit values
The limit value formed by the logical combination is called "LIMIT LOGIC".
SENTRON PAC4200 provides parameterizable logic for combining the limit values that
supports brackets, takes account of priority rules, and allows logical negation.
The logic is represented on the display using the graphic symbols familiar from digital
technology: Four logic function blocks are connected upstream of one higher-level logic
function block. Each of the upstream logic function blocks has 4 usable inputs.
Figure 3-12 LIMIT LOGIC
The following logic operations can be selected for each logic function block:
●
AND (AND operation)
● NAND (NOT AND operation)
● OR (OR operation)
● NOR (NOT OR operation)
● XOR (EXCLUSIVE OR operation)
● XNOR (EXCLUSIVE NOT OR operation)
Any limit values and the digital inputs of SENTRON PAC4200 can be selected at the inputs
of the upstream logic function blocks. The input value is the truth value of the monitored
signal:
●
True: Limit value is violated or input is active
● False: Limit value is not violated or input is not active
Displaying limit violations
SENTRON PAC4200 outputs limit violations at the digital output or via the interfaces.
Limit violations are countable. One of the limit values can be assigned to the universal
counter.
Limit violations are recorded as events with additional information on the monitored
measured variable and the monitored threshold