NOSHOK 1900 Series Current Loop Powered Process Indicators - Manual (Page 3)

3
WIRING CONNECTIONS
All conductors should meet voltage and current ratings for
each terminal. Also cabling should conform to appropriate
standards of good installation, local codes and regulations. It is
recommended that power supplied to the unit (ac or dc) be
protected by a fuse or circuit breaker.
The electrical connections are made via screw-clamp
terminals located on the back of the unit. When wiring the unit,
use the label to identify the wire position with the proper
function. Strip the wire, leaving approximately ¼" of bare wire
(stranded wires should be tinned with solder). Insert the wire
into the screw-clamp terminal and tighten the screw until the
wire is clamped tightly. Each terminal can accept up to two #14
AWG wires.
EMC INSTALLATION GUIDELINES
Although this unit is designed with a high degree of immunity to
ElectroMagnetic Interference (EMI), proper installation and wiring methods
must be followed to ensure compatibility in each application. The type of the
electrical noise, source or coupling method into the unit may be different for
various installations. Cable length, routing and shield termination are very
important and can mean the difference between a successful installation or a
troublesome installation. Listed below are some EMC guidelines for successful
installation in an industrial environment.
1. Use shielded (screened) cables for all Signal and Control inputs. The shield
(screen) pigtail connection should be made as short as possible. The
connection point for the shield depends somewhat upon the application.
Listed below are the recommended methods of connecting the shield, in order
of their effectiveness.
a. Connect the shield only at the panel where the unit is mounted to earth
ground (protective earth).
b. Connect the shield to earth ground at both ends of the cable, usually when
the noise source frequency is above 1 MHz.
c. Connect the shield to common of the unit and leave the other end of the
shield unconnected and insulated from earth ground.
2. Never run Signal or Control cables in the same conduit or raceway with AC
power lines, conductors feeding motors, solenoids, SCR controls, and
heaters, etc. The cables should be run in metal conduit that is properly
grounded. This is especially useful in applications where cable runs are long
and portable two-way radios are used in close proximity or if the installation
is near a commercial radio transmitter.
3. Signal or control cables within an enclosure should be routed as far away as
possible from contactors, control relays, transformers, and other noisy
components.
4. In extremely high EMI environments, the use of external EMI suppression
devices, such as ferrite suppression cores, is effective. Install them on Signal
and Control cables as close to the unit as possible. Loop the cable through the
core several times or use multiple cores on each cable for additional
protection. Install line filters on the power input cable to the unit to suppress
power line interference. Install them near the power entry point of the
enclosure. The following EMI suppression devices (or equivalent) are
recommended:
Ferrite Suppression Cores for signal and control cables:
Fair-Rite # 0443167251
TDK # ZCAT3035-1330A
Steward #28B2029-0A0
Line Filters for input power cables:
Schaffner # FN610-1/07
Schaffner # FN670-1.8/07
Corcom #1VR3
Note: Reference manufacturer’s instructions when installing a line filter.
5. Long cable runs are more susceptible to EMI pickup than short cable runs.
Therefore, keep cable runs as short as possible.
1900C SIGNAL INPUT
The current range is selected by setting DIP switch S1 to the OFF position
for a 4 mA to 20 mA input or ON for a 10 mA to 50 mA input. Attach the signal
wires to terminals 3 (SIG-) and 4 (SIG+) observing the correct polarity.
The (SIG-) signal input circuit is not reverse polarity protected.
Backlight Power (1900C-3/1900C-4 only)
Attach a 9 mA to 28 V dc supply to terminals 1 (COM) and 2 (V+) to power
the backlight. Terminals 3 (SIG-) and 1 (COM) are ac coupled with a capacitor.
This limits the isolation between these terminals to 50 V dc maximum.
OFFSET ADJUSTMENTS
The minimum currents are not zero based with 4 mA to 20 mA and 10 mA to
50 mA signals. To obtain a zero minimum display reading, the display must be
offset. The display on the 1900C can be offset by adjusting the Coarse and Fine
Offset pots.
SPAN ADJUSTMENTS
Span is defined as the numerical range that the display traverses, disregarding
the decimal point, when the input signal is varied from minimum to maximum
(4 mA to 20 mA or 10 mA to 50 mA). For example; if a unit is to display 250
@ 4 mA and 1000 @ 20 mA, the span is 750 (the difference between 250 and 1000).
Had the minimum display been -250, the span would be 1250 (1000 - (-250) = 1250).
The 1900C unit can be set to operate over a wide span range by adjusting the
Coarse and Fine Span adjustment pots. The Coarse Span pot is used to get the
display to within a couple of counts of the desired reading, and the Fine Span
pot is used to adjust for the exact reading.
WARNING - EXPLOSION HAZARD - DO NOT DISCONNECT
EQUIPMENT UNLESS POWER HAS BEEN SWITCHED OFF
OR THE AREA IS KNOWN TO BE NON-HAZARDOUS.
1900C