22
The 1250B may be ordered with isolated input terminals. In cases where there is a
compromise of the system isolation to earth ground, this option will prevent AC voltage from
becoming impressed upon the analog output signal (See Note at the end of section 3.1). This
option consists of two small signal isolation transformers installed in the signal input
circuitry. Performance and reliability are not affected when this option is installed.
3.3
High / Low Relay Limits Option “-R”
The High / Low Relay Limits may be used as feedback in a control system or as an
alarm when the position has exceeded desired limits. The high and low relays are normally
open, dry contacts that do not latch when they are turned on. When the position value falls
below the low relay limit, the low relay turns on. When the position value rises above the low
relay limit, the low relay will turn off. When the value rises above the high relay limit the
high relay turns on. When the value falls below the high relay limit, the high relay turns off.
Figure 3.1 Relay Field Wiring Diagram
3.3.1 Programming the Relay Limits
Before relay limits can be set, the relay option must be enabled in the menu. To do
this use the
OP 1, rLY E, RLYENA
command to toggle the condition to “
ON”
. If this
condition is left in the OFF state an error message “ERR 1” will appear when attempting to
set relay limits.
If the 1250B is programmed for a Scaled Mode, use the
OP 7, rLY L, RLYLOW
command to set the Low Relay Limit and the
OP 8, rLY H, RLYHIGH
command to set the
High Relay Limit.
If the 1250B is programmed for a Segmented Mode, use the
OP 24, rL Lt, RLYLT
command to set the Low Relay Limit and the
OP 25, rL Ht, RLYHT
command to set the
High Relay Limit.