ROC364 Instruction Manual
1-7
General Information
Rev Jun/05
For an analog I/O channel
, the Duty Cycle is approximated by estimating the percentage of
time the channel spends in the upper half of its range (span) of operation. For example, if an
Analog Input wired as a current loop (4 to 20 milliamps) device operates in the upper half of its
range 75% of the time, then 0.75 would be used as the Duty Cycle. If the analog channel
generally operates around the midpoint of its span, use 0.5 as the Duty Cycle.
2.
To calculate the total power consumed by an I/O channel, first select either the
12 Volt
or
24
Volt
column in Table 1-1 or Table 1-2 and read the minimum (
P
min
) and maximum (
P
max
) power
consumption value from the table for the desired I/O channel.
3.
Calculate the power consumption for a channel with the Duty Cycle using the following equation
taken into account:
Power
=
(P
max
x
Duty Cycle) + [P
min
(1 – Duty Cycle)]
4.
Multiply this value by the quantity (
QTY
) of I/O channels with the same Duty Cycle and enter
the calculated value in the
Sub-Total
column.
5.
Repeat the procedure for all other I/O channels used.
6.
Total the values in the
I/O Modules Sub-Total
column in Table 1-2.
7.
Enter the
I/O Modules Total
value in Table 1-1.
8.
Calculate
the
Radio Power Consumption
total. Refer to Section 1.5.2, Determining Radio
Power Consumption, on page 1-8.
9.
Enter the
Radio Power Consumption Total
value in Table 1-1.
10.
Calculate
Total
power consumption in Table 1-1.
11.
Add the
power consumption
(in mW) of any
other devices
used with the ROC in the same
power system, but not accounted for in the tables to the Total power consumption value in Table
1-1. Refer to Section 1.5.3, Totaling Power Requirements, on page 1-9.
Table 1-1. Power Consumption of the ROC364 and Powered Devices
Power Consumption (mW)
12 Volt
24 Volt
Device
P
min
P
max
P
min
P
max
QTY
Duty
Cycle
Sub-
Total
(mW)
MCU and I/O Module Rack
915
1705
1
N/A
I/O Converter Card
1
230
N/A
N/A
Local Display Panel
25
25
N/A
Serial Communications Card
135
135
N/A
Dial-up Modem Card
395
395
N/A
Leased Line Modem Card
110
110
N/A
Radio Modem Card
110
110
N/A
I/O Modules Total from Table 1-2
N/A
N/A
N/A
Radio (Section 1.5.2)
N/A
N/A
N/A
TOTAL
NOTE:
1. The power drawn by field devices connected to I/O modules is included in the P
max
figures in Table
1-2.
