Emerson 3051N manual Wiring, Power Supply Load Limitations

Reference Manual

00809-0100-4808, Rev CA June 2008

Rosemount 3051N

FIGURE 3-7. Power Supply Load Limitations.

Max. Loop Resistance = 43.5 (Power Supply Voltage – 10.5) ohms

Load (ohms)

1935
1500
1000	Design
500	Region
0

10.5	20	30	40	55
		Voltage (V dc)

	Communication requires a minimum loop resistance of 250 ohms.
Wiring	To make connections, perform the following procedure:
	1. Remove the housing cover on the side marked “FIELD TERMINALS.” Do
	not remove the cover in explosive atmospheres when the circuit is alive.
	All power to the transmitter is supplied over the signal wiring.
	2. Connect the lead that originates at the positive side of the power supply
	to the terminal marked “+” and the lead that originates from the negative
	side of the power supply to the terminal marked “–”. Avoid contact with
	the leads and terminals. Do not connect the powered signal wiring to the
	test terminals. Power could damage the test diode in the test connection.
	3. Plug and seal unused conduit connections on the transmitter housing to
	avoid moisture accumulation in the terminal side of the housing. If you do
	not seal the unused connections, mount the transmitter with the electrical
	housing positioned downward for drainage. Install wiring with a drip loop.
	Arrange the drip loop so the bottom is lower than the conduit connections
	and the transmitter housing.
	NOTE
	Signal wiring needs to be shielded, but use twisted pairs for best results. In
	order to ensure proper communication, use 24 AWG or larger wire, and do not
	exceed 5000 feet (1 500 meters).
	Do not use inductive-based transient protectors, including the Rosemount
	470, as they can adversely affect the output of Rosemount 3051N 4–20 mA
	transmitters.The Rosemount 3051N includes the transient protection terminal
	block (T1) as standard.
	Signal Wiring Grounding
	Do not run signal wiring in conduit or open trays with power wiring, or near
	heavy electrical equipment. You may ground the signal wiring at any one point
	on the signal loop, or leave it ungrounded. The negative terminal of the power
	supply is a recommended grounding point.

See “Safety Messages” on page 3-1for warning information.

3-13