NOTE: Latching relays are used in this product in conjunction with an advanced relay drive circuit. During
commissioning, on initial power up, or after switch settings have been modified, one trip operation must
be completed in order to synchronise the latching relay(s). Once this cycle has been completed the unit
will function correctly during normal operation cycles. On power down the trip contacts will rest as for a
-25 % (0 mA) process value and take this state indefinitely until power up. The initial power up cycle will
only be required again if the unit switch settings are changed, or the unit is removed from the installation
and is subjected to shocks greater that 12 G, i.e. during transit.
This section deals with the trip setup. Three adjustments are available to the user:
High/Low alarm selection switch located on the side of the trip.
Set point adjustment -15 turn front panel potentiometer provides (0 to 100) % set point range.
Hysteresis adjustment - single turn potentiometer located on front panel provides (0.1 to 5) % set
point hysteresis. Hysteresis is provided to stop relay chatter at the trip point, the amount of
hysteresis required will be dependent on the process signal noise.
Page 3
Page 4
(4 to 20) mA
(4 to 20) mA
R
C
SNUBBER
LOAD
LOAD
AC
DC
IN
TRIP
HYS
SEM1401
OUT
C
N/C
N/O
IN
TRIP
HYS
SEM1401
OUT
C
N/C
N/O
Figure 1
Figure 2
(4 to 20) mA
IN
N/C
N/O
C
H
L
OUT
-
+
4.0 ALARM TRIP SETUP
A red LED indicates alarm state ON.
With care, the SEM1401 trip set point may be set up in the process but the task is greatly simplified by
replacing the process signal with a adjustable (4 to 20) mA current source, to simulate the (4 to 20) mA
process signal.
The set up process is as follows:
1.
First decide on the type of trip required, “High” for alarm ON state above set point, or “Low” for
alarm ON state below set point. Set the High/Low alarm selection switch on the side of the
enclosure to the desired setting, by inserting a 3 mm blade screw driver into the hole and apply
one press against the switch plunger. This will toggle the switch between the the two alarm settings
being :
High alarm state - plunger out (flush with the enclosure inside face)
Low alarm state - plunger in (depressed below inside face)
2.
Using a 3 mm screw driver, turn the Hysteresis control full anti-clockwise to set the hysteresis
to 0.1 %
3.
Set the process current to the desired trip alarm setting, then using a 3 mm screw driver adjust the
set point until the alarm changes state. Clockwise to increase, anticlockwise to decrease. Adjust
the set point backwards and forwards until it is positioned at the point at which the alarm LED has
just come on.
4.
Set the hysteresis control to the desired value, as a guide fully clockwise sets 5 %, mid position
2.5 %.
5.
Now raise and lower the process input signal about the trip setting and ensure the alarm trips at set
point and trips off at set point plus (minus) hysteresis. If required fine adjust settings.
6.
Now fully operate the system, it may be found necessary to adjust the hysteresis setting during
operation depending upon the fluctuation or noise present on the process signal.
Once setup and operating satisfactorily the trip amplifier requires no further user adjustments.
5.0 OPERATION
