7
3.3 Electrical Connections
All of the electrical connections to the instrument are made through the
field terminal box, which should be located directly under the sensor
portion of the instrument. The connections are labeled within the
terminal box and are self-descriptive (see Figure 5). Please follow all
local and government recommendations and methods for installation
of electrical connections to and between the instrument and other
peripheral devices.
Plugs are inserted into the alarm and 4-20mA/RS-485 cable bulkheads
when shipped, to ensure a watertight seal. These plugs should be
removed and discarded when cabling to either of these connections.
The power cable bulkhead will accept cable diameters from 5.8mm
(.230 in.) up to 10 mm (.395 in.). All terminals are designed to accept
wires in the range of 14-28 AWG. All wires should be stripped to a
length of 6 mm (¼"). A strain relief strap is provided to reduce tension
on the power terminals.
Figure 5: Electrical Connections for the Instrument
It is the user’s responsibility to assure that the watertight seal is maintained
after the terminal box has been wired for operation. If any of the bulkheads
are not tightened properly around a cable or plug, the ratings of the
instrument will be jeopardized and there is a possibility of creating a
shock hazard.
Only qualified electricians should be allowed to perform
the installation of the instrument as it involves a line
voltage that could endanger life.
3.3.1 Power
The instrument is equipped with a 100-240 VAC, 47-63 Hz switching
power supply; please verify that the line voltage falls within these
specifications. It is recommended that a circuit breaker be placed
prior to the power connection to allow for service. While making
connections, refer to Figure 5.
The AccUView LED is not supplied
with a power cord.
3.3.2 RS-485
The RS-485 Modbus or special protocol half-duplex (2-wire) digital
interface operates with differential levels that are less susceptible to
electrical interferences. This is why cable lengths up to 3000 ft can be
implemented. The last device on each bus may require terminating with
a 120-ohm resistor to eliminate signal reflection on the line. Do not run
RS-485 cables in the same conduit as power.
To prevent damage to the instrument, ensure that power is
disconnected prior to making connections. For ease of connecting,
remove the plug in terminal block. Connections are labeled beneath
this termination.
3.3.3 Relays
The Alarm 1 and Alarm 2 relays are mechanical relays rated at 240 VAC
2A. Please note that the relays are labeled NO (Normally Open), NC
(Normally Closed) and C (Common). As these alarms are configured
fail-safe, the normal condition is with power applied to the
AccUView LED and in a non-alarm condition. Operation
of these alarms is covered in section
7.4 Configuring
the Alarms.
3.3.4 4-20 mA
The 4-20 mA output is driven by a 15 VDC power source and can
drive recorder loads up to 600 ohms. Do not run 4-20 mA cables in
the same conduit as power. Operation of this output is
covered in section
7.2 Setting the 4-20 mA
. The outputs
are equipped standard with an installed loop powered
isolator (500V isolation).
To prevent damage to the instrument, ensure that power is
disconnected prior to making connections. For ease of connecting,
remove the plug in terminal block. Polarity of the connections is labeled
beneath this termination.
Sensor
Interconnect
Cable
Field Terminal Box
(with lid removed)
Liquid Tight Plugs
Power
Cable
Bulkhead
Alarm
Cable
Bulkhead
4-20mA/
RS-485
Cable
Bulkhead
Power Supply
Terminal Block
Alarms
Terminal Block
240 VAC 2A
4-20mA/RS-485
Terminal Block
Power Cable
Strain Relief
