Reference Manual
00809-0100-4716, Rev JA
May 2008
Rosemount 3095 MultiVariable
2-12
Electrical (HART) The signal terminals are located in a compartment of the electronics housing
separate from the transmitter electronics.
Power Supply
The dc power supply should provide power with less than 2% ripple. The total
resistance load is the sum of the resistance of the signal leads and the load
resistance of the controller, indicator, and related pieces. Note that the
resistance of intrinsic safety barriers, if used, must be included.
NOTE
A loop resistance between 250–1100 ohms inclusive is required to
communicate with a personal computer. With 250 ohms of loop resistance, a
power supply voltage of at least 16.5 V dc is required.
(1)
If a single power supply is used to power more than one 3095 transmitter, the
power supply used, and circuitry common to the transmitters, should not have
more than 20 ohms of impedance at 1200 Hz.
Figure 2-5. Power Supply Load
Limitations.
Electrical (FOUNDATION
Fieldbus)
Proper electrical installation is necessary to prevent errors due to improper
grounding and electrical noise. Shielded, twisted pair cable should be used for
best results in electrically noisy environments. Cable Type A is recommended
by FOUNDATION fieldbus.
NOTE
After a device labeled with multiple approval types is installed, it should not be
reinstalled using any of the other labeled approval types. To ensure this, the
approval label should be permanently marked to distinguish the used from the
unused approval type(s).
Field Wiring
All power to the transmitter is supplied over the signal wiring. For best
installation practices, use a fieldbus type A cable. Do not run unshielded
signal wiring in conduit or open trays with power wiring or near heavy
electrical equipment. Do not remove the transmitter cover in explosive
atmospheres when the circuit is alive.
(1) Quick troubleshooting check: There must be at least 11.0 V dc across the transmitter
terminals.
Max. Loop Resistance = Power Supply Voltage-11.0
0.022
2000
Load (Ohms)
0
11.0 42.4
(1)
55
Operating Region
(1) For CSA approval, power supply must not exceed 42.4 V dc.
(2) HART protocol communication requires a loop resistance value
between 250-1100 ohms, inclusive.
Power Supply
250
16.5
(2)
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