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ROC800-Series Instruction Manual

Revised Jul-14

Power Connections

3-11

detect circuit includes approximately 0.75 Volts dc of hysteresis

between turn-off and turn-on levels.

For further information on the STATUS LED functions, refer to

Table

2-2

in

Chapter 2, Installation and Use

.

3.2 Determining Power Consumption

Determining the power consumption requirements for a ROC800

configuration involves the following steps:

1.

Determine your ideal ROC800 configuration, which includes

identifying all modules, device relays, meters, solenoids, radios,

transmitters, and other devices that may receive DC power from the

complete ROC800 configuration (base unit and EXPs).

Note

:

You should also identify any devices (such as a touch screen

panel) that may be powered by the same system but not

necessarily by the ROC800.

2.

Calculate the “worst-case” DC power consumption for that

configuration by totaling the combined power draw required for

all

installed modules, as well as accounting for the power any modules

provide to external devices (through the use of +T).

Note

:

“+T” describes the isolated power some modules (such as

AI, AO, PI, and HART) may supply to external devices,

such as 4–20 mA pressure and temperature transducers.

3.

Verify that the power input module you intend to use can meet the

power requirements calculated in the first step.

This verification helps you identify and anticipate power demands

from +T external devices that exceed the capabilities of the PM-12

or PM-24 Power Input modules. In this case, you can then make

arrangements to externally power these field devices.

4.

“Tune” (if necessary) the configuration by providing external power

or re-assessing the configuration to lessen the power requirements

from the ROC800.

To assist you in this process, this chapter contains a series of worksheets

(

Tables 3-5

through

3-18

) that help you to identify and assess the power

requirements for each component of your ROC800 system.

Table 3-5

identifies the power requirements related to the ROC800 and

summarizes the power requirements you identify on

Tables 3-6

through

3-18

. (Complete

Tables 3-6

through

3-17

to calculate the power

consumption for each of the I/O modules, and then transfer those results

to

Table 3-5

.) Completing

Table 3-5

enables you to quickly determine

whether the power input module you intend to use is sufficient for your

configuration. If the power module is not sufficient, you can then review