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Reference Manual
00809-0200-4728, Rev SA
Operation and Maintenance
July 2018
Operation and Maintenance
The power supplied to the transmitter is determined by the total loop resistance and should not drop
below the lift-off voltage. The lift-off voltage is the minimum supply voltage required for any given total
loop resistance. If the power drops below the lift-off voltage while the transmitter is being configured,
the transmitter may output incorrect information.
The DC power supply should provide power with less than two percent ripple. The total resistance load is
the sum of the resistance of the signal leads and the load resistance of any controller, indicator, or related
piece of equipment in the loop. Note that the resistance of intrinsic safety barriers, if used, must be
included.
Note
Permanent damage to the transmitter could result if the voltage drops below 12.0 Vdc at the power
terminals, when changing transmitter configuration parameters.
Figure 4-4. Load Limits
Maximum Load = 40.8
(Supply voltage - 12.0)
1240
1000
750
250
0
10
12.0
20
30
40 42.4
Supply voltage (Vdc)
Operating
region
4–20 mA dc
Lo
ad
(
O
h
m
s)
500
1100
Summary of Contents for Rosemount 644 with HART Protocol
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Page 8: ...vi Reference Manual 00809 0200 4728 Rev SA Title Page July 2018 Title Page ...
Page 48: ...40 Reference Manual 00809 0200 4728 Rev SA Configuration July 2018 Configuration ...
Page 62: ...54 Reference Manual 00809 0200 4728 Rev SA Installation July 2018 Installation ...
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