Emerson 00809-0100-4514, 1154 Conduit, Electrical Considerations, Rosemount, Reference Manual

Rosemount 1154

Reference Manual

00809-0100-4514, Rev BA January 2008

The piping between the process and the transmitter must transfer the pressure measured at the process taps to the transmitter. Possible sources of error in this pressure transfer are:

	• Leaks
	• Friction loss (particularly if purging is used)
	• Trapped gas in a liquid line or trapped liquid in a gas line (head error)
	• Temperature-induced density variation between legs (head error), for
	differential transmitters
	To minimize the possibility of errors, take the following precautions:
	• Make impulse tubing as short as possible.
	• Slope tubing at least one inch per foot up toward the process
	connections for liquid and steam.
	• Slope tubing at least one inch per foot down toward the process
	connections for gas.
	• Avoid high points in liquid lines and low points in gas lines.
	• Use impulse tubing of sufficient diameter to avoid friction effects.
	• Ensure that all gas is vented from liquid tubing legs.
	• Ensure that impulse tubing is of adequate strength to be compatible
	with anticipated pressures.
	For differential transmitters, also consider the following:
	• Keep both impulse legs at the same temperature.
	• When using sealing fluid, fill both piping legs to the same level.
	• When purging, make the purge connection close to the process taps
	and purge through equal lengths of the same size tubing. Avoid purging
	through the transmitter.
Conduit	The conduit connection to the transmitter is 1/2–14 NPT. Use a qualified
	conduit seal at the conduit entry to prevent moisture from accumulating in the
	terminal side of the housing during accident conditions. To prevent the conduit
	from adding mechanical stress to the transmitter during seismic disturbances,
	use flexible conduit or support the conduit near the transmitter. Install the
	conduit seal in accordance with the manufacturer’s instructions or use the
	procedure on page 2-8.

ELECTRICAL CONSIDERATIONS

This section contains information that you should consider when preparing to make electrical connections to the transmitter. Read this section carefully before proceeding to the electrical installation procedures.

The Rosemount 1154 pressure transmitter provides a 4–20 mA signal when connected to a suitable dc power source. Figure 2-2 on page 2-5shows a typical signal loop consisting of transmitter, power supply, and various receivers (controller, indicator, computer, etc.). The power supply must supply at least 12 volts to the transmitter terminals at 30 mA (overscale) signal, or the maximum output current required for proper system operation. Any power supply ripple appears in the output load. The supply voltage versus load limitation relationship is shown in Figure 2-3 on page 2-5.See qualification report D8400102 for details. The load is the sum of the resistance of the signal leads and the load resistance of the receivers.

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