Emerson manual General Considerations, Special Draft Range Considerations, Rosemount 3051N

Rosemount 3051N

Reference Manual

00809-0100-4808, Rev CA June 2008

GENERAL CONSIDERATIONS

Special Draft Range Considerations

Measurement accuracy depends upon proper installation of the transmitter and impulse piping. Mount the transmitter close to the process and use a minimum of piping to achieve best accuracy. Keep in mind the need for easy access, personnel safety, practical field calibration, and a suitable transmitter environment. Install the transmitter to minimize vibration, shock, and temperature fluctuation.

Installation

It is best to mount the transmitter with the isolating diaphragms parallel to the ground. Installing the transmitter in this way reduces oil head effect and provides for optimal temperature performance.

Be sure the transmitter is securely mounted. Tilting of the transmitter may cause a zero shift in the transmitter output.

Reducing Process Noise

It is often difficult to isolate the actual process variable from process noise in draft range applications. Pressure fluctuations and air currents can make accurate draft range measurements difficult to obtain.

There are two recommended methods of reducing process noise: output damping and, in gage applications, reference side filtering.

Output Damping

The output damping for the Rosemount 3051ND0 is factory set to 3.2 seconds as a default. If the transmitter output is still noisy, increase the damping time. If faster response is needed, decrease the damping time. Damping adjustment information is available in Section 2: Transmitter Functions.

Reference Side Filtering

MECHANICAL CONSIDERATIONS

In gage applications it is important to minimize fluctuations in atmospheric pressure to which the low side isolator is exposed. One method of reducing fluctuations in atmospheric pressure is to attach a length of tubing to the reference side of the transmitter to act as a pressure buffer. Another method is to plumb the reference side to a chamber that has a small vent to atmosphere. If multiple draft transmitters are being used in an application, the reference side of each device can be plumbed to a chamber to achieve a common gage reference.

IMPORTANT

Install the enclosed pipe plug in unused conduit openings with a minimum of five threads engaged to comply with explosion proof requirements.

The following figures show dimensional drawings and installation examples of the Rosemount 3051N transmitters, including mounting brackets.

NOTE

For Rosemount 3051ND0 and 3051ND1, mount the transmitter solidly to prevent tilting. A tilt in the physical transmitter may cause a zero shift in the transmitter output.

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