DCA
Page 19
3.
Set input #2 to desired percentage above or below
reference.
4.
Set trip points as appropriate, using UNC pot for
UPPER normally closed alarm, UNO pot for
UPPER normally open; LNC for LOWER normally
closed, and LNO for LOWER normally open.
Base settings on input #2.
Units factory-configured as high alarms will “trip”
when input #2 exceeds the desired difference.
Low alarms “trip” when input #2 falls below
desired difference.
For Example:
A DA-equipped DCA is rated for two, 4-20 mA inputs
(“2X” in the model number). The application calls for
an alarm condition when input #2 varies more than
25% of span from the reference input.
Span = 16 mA
25% of 16 = 4 mA
The reference input is set to 50% of rated span, or 12
mA. Input #2 is set 25% higher, 16 mA.
The trip point pots are turned clockwise until relays
change state.
Regardless of how the reference input is varied, from
4 to 20 mA, as long as input #2 is likewise varied at a
50% offset, the alarms are not “tripped”.
However, if the reference is at 12 mA and input #2 is
at 20 mA, the high-alarm relay will indicate an alarm
condition. Likewise, if the reference is at 12 mA and
input #2 is at 14 mA, the low-alarm relay will indicate
an alarm.
Installation
Installing the DCA is typically accomplished by
physically mounting the unit, then effecting the
electrical connections.
Mounting
Figures 15 and 16, respectively, show the outline
dimensions of the DCA in the STD and the PC
housing styles. The drawing of the STD housing
includes the dimensions of the U-bracket, typically
included with that type of DCA, and also of the side
housing used for DCA’s equipped with the DPDT
option.
Always try to install the DCA in an area relatively free
of dust, excessive moisture, or corrosives.
Contact your Moore Industries Sales Representative
for information on other types of DCA housings,
enclosures, and mounting hardware.
Making Electrical Connections
Figure 17 illustrates the installation hookup for the
unit. Refer to the terminal location figures in the
Calibration Section when making the electrical
connections associated with installing the DCA.
Though there is no special wiring required for standard
connections, the use of shielded, twisted wiring is
recommended for all low-level signals, or where
connecting leads are run close to other services such
as power wiring. Ground the shield wire as close to
the DCA as possible in the installation.
