YOKOGAWA F3CU04-0S, User Manual

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C3-17
IM 34M06H62-02E 2nd Edition : June 2008-00

Automatic Changeover Using Upper Limit (SELMD: 1)
In this mode, Input 1 is used when it is not higher than SELH, and Input 2 is used when
Input 1 is higher than SELH, as follows:
Input 1

SELH: Input 1 is selected.
Input 1 > SELH: Input 2 is selected.

Manual Changeover Using Input Selection (SELMD: 2)
Switches between input 1 and input 2 according to the Input Selection (INSEL)
parameter, as follows:
INSEL = 0: Input 1 is selected.
INSEL = 1: Input 2 is selected.
The PV may change abruptly when changeover is made between Input 1 and Input 2,
as illustrated below.
1 0
Input 2
Input 1
PV
INSEL 0
Figure C3.8 Changeover Using Input Selection (INSEL) Parameter
TIP
If two inputs have different values, switching between the two inputs would result in an abrupt change in
controlled output. To prevent this, this mode uses the average of the two inputs as the PV value within the
overlapping range. For this to work in Automatic Changeover Using Temperature Range mode (SELMD
= 0), you must define input 1 and input 2 with overlapping ranges.