Panametrics Aurora H2O, User Manual

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Aurora H2O User’s Manual 15
Chapter 2. Installation
2.8 Making Electrical Connections (cont.)
Note: Supply connection wiring shall be rated at least 10°C above the rate maximum service temperature of 85°C,
be stripped back 5/16 in. (8 mm) and torqued to a minimum of 4.4 in. lb. (0.5 Nm).
3. Run the AC power connections to the Power Terminal Block shown in Figure 26 below. It is recommended to use
12-18 AWG (3.3 - 0.82 mm
2
) power wiring.
Figure 26: Power Terminal Block
4. Use wiring conduit runs, separate from the Aurora H2O main power, for all I/O (Input/Output) leads. Wire up to
three 4-20mA outputs to the terminals labeled A, B, and C. The three analog outputs A, B and C (0-20mA or
4-20mA) are internally powered by the Aurora H2O . Use shielded 18-22 AWG (0.82–0.33 mm
2
) twisted pair wire,
and ground the shield at one end only. Wire up digital communications to Port 1 and/or Port 2 as labeled.
5. Either digital port may be configured for RS-232 or RS-485. Port 1 is designated as “SCADA.” Port 2 is designated as
“SERVICE.” For operation on RS-485, 2-wire, half-duplex bus, attach the RS-485(+) to (+), and the RS-485(–) to (–
). Per Modbus-IDA specifications, a third, common conductor must also interconnect all the devices of the bus.
Attach the common conductor to RTN.
Note: For an RS-485 Multi-drop Network, a terminating resistor must be installed across the Aurora H2O RS-485
terminals, or an internal terminating resistor can be applied. See below.
• When using the Aurora H2O in RS-485 mode, and to prevent signal reflections on the high-speed RS-485
connections, it is recommended that the far end of the RS-485 lines be terminated properly. The termination
can be accomplished in one of two ways:
•
Connect 120

, 1/4 W leaded resistors across the + and – terminals of ports 1 and 2 (both ports or
whichever one will be in use)
•
Using long-nose pliers, move jumpers J15 and J16 from pins 2 and 3 (default setting from factory) to pins
1 and 2 (see Figure 27 on page 16). J16 is the termination for port 1 and J15 is the termination for port 2. It
is also recommended that basic ESD precautions such as grounded wrist straps be used for this procedure.