Omega Products PX751 Installation Manual

User’s Guide

Model PX751 Pressure Transmitter

http://www.omega.com

e-mail: [e-mail]

Pressure Transmitter

PX751

OMEGAnet® On-Line Service Internet e-mail
http://www.omega.com [e-mail]

Servicing North America:

USA: One Omega Drive, Box 4047
ISO 9001 Certified Stamford, CT 06907-0047
Tel: [phone] FAX: [phone]
e-mail: [e-mail]
Canada: 976 Bergar

Laval (Quebec) H7L 5A1
Tel: [phone] FAX: [phone]
e-mail: [e-mail]

For immediate technical or application assistance:

USA and Canada: Sales Service: 1-800-826-6342 / 1-800-TC-OMEGASM
Customer Service: 1-800-622-2378 / 1-800-622-BESTSM
Engineering Service: 1-800-872-9436 / 1-800-USA-WHENSM
TELEX: 996404 EASYLINK: 62968934 CABLE: OMEGA
Mexico and
Latin America: Tel: [phone] FAX: [phone]

En Espan˜ol: (95) 203-359-7803 e-mail: [e-mail]

Servicing Europe:

Benelux: Postbus 8034, 1180 LA Amstelveen, The Netherlands
Tel: [phone] FAX: [phone]

Toll Free in Benelux: 0800 0993344

e-mail: [e-mail]
Czech Republic: ul. Rude armady 1868, 733 01 Karvina-Hranice
Tel: [phone] FAX: [phone]

Toll Free: 0800-1-66342 e-mail: [e-mail]
France: 9, rue Denis Papin, 78190 Trappes
Tel: [phone] FAX: [phone]
Toll Free in France: 0800-4-06342

e-mail: [e-mail]
Germany/Austria: Daimlerstrasse 26, D-75392 Deckenpfronn, Germany
Tel: [phone] FAX: [phone]
Toll Free in Germany: 0130 11 21 66

e-mail: [e-mail]
United Kingdom: One Omega Drive, River Bend Technology Centre
ISO 9002 Certified Northbank, Irlam, Manchester

M44 5EX, England

Tel: [phone] FAX: [phone]

Toll Free in the United Kingdom: 0800-488-488

e-mail: [e-mail]

It is the policy of OMEGA to comply with all worldwide safety and EMC/EMI regulations that apply. OMEGA is constantly pursuing certification of
its products to the European New Approach Directives. OMEGA will add the CE mark to every appropriate device upon certification.

The information contained in this document is believed to be correct, but OMEGA Engineering, Inc. accepts
no liability for any errors it contains, and reserves the right to alter specifications without notice.
WARNING: These products are not designed for use in, and should not be used for, patient-connected applications.

Table of Contents

SECTION 1 Introduction

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Models Covered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Using this manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

New Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1-4

SECTION 2 Commissioning

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Safety Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Setting the Loop to Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Fast key sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Configure the Analog Output Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Set the Process Variable Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Set the Output Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Rerange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Set the Damping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

LCD Meter Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Diagnostics and Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Transmitter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Loop Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

Calibration Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Sensor Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Analog Output Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

Compensating Model PX751 Range 4 and 5

Differential Pressure Transmitters for Line Pressure . . . . . . . . . . . . . . . 2-16

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SECTION 3 Installation

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Safety Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Mechanical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Mounting Brackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Housing Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Mounting Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Electrical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Failure Mode Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

Failure Mode Alarm vs. Saturation Output Values . . . . . . . . . . . . . . . . . . 3-12

SECTION 4 Troubleshooting

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

SECTION 5 Reference Data

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Transmitter Range and Sensor Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Bolt Identification and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

APPENDIX A HART® Communicator

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

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SECTION

1

Introduction

OVERVIEW

This section outlines the models covered and the organization of this manual.

The following performance limitations may inhibit efficient or safe operation. Critical applications
should have appropriate diagnostic and backup systems in place.

Pressure transmitters contain an internal fill fluid. It is used to transmit the process pressure
through the isolating diaphragms to the pressure sensing element. In rare cases, oil leak paths
in oil-filled pressure transmitters can be created. Possible causes include: physical damage to
the isolator diaphragms, process fluid freezing, isolator corrosion due to an incompatible
process fluid, etc.

A transmitter with an oil fill fluid leak can continue to perform normally for a period of time.
Sustained oil loss will eventually cause one or more of the operating parameters to exceed
published specifications while a small drift in operating point output continues. Symptoms of
advanced oil loss and other unrelated problems include:

n Sustained drift rate in true zero and span or operating point output or both
n Sluggish response to increasing or decreasing pressure or both
n Limited output rate or very nonlinear output or both
n Change in output process noise
n Noticeable drift in operating point output
n Abrupt increase in drift rate of true zero or span or both
n Unstable output
n Output saturated high or low

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1-1

MODELS COVERED

This manual provides basic installation, commissioning, and troubleshooting

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information for the following Omega® Model PX751 Pressure Transmitters:
Model PX751CD — Differential Pressure Transmitter

measures differential pressure from 0.5 inH
superior performance including 0.075% accuracy and 100:1 rangeability.

Model PX751CG — Gage Pressure Transmitter

measures gage pressure from 2.5 inH
proven capacitance cell technology.

Model PX751CA — Absolute Pressure Transmitter

measures absolute pressure from 0.167 to 4,000 psia (8.6 mmHga to 27580 kPa)
using patented piezoresistive silicon sensor.

Model PX751H — High Process Temperature Pressure Transmitter

provides high process temperature capability to 375 °F (191°C), without the use of
remote diaphragm seals or capillaries. These transmitters are available for
differential and gage configurations (PX751HD and PX751HG).

Model PX751P —

provides 0.05% accuracy. The Model PX751P is the most accurate pressure transmitter
available and is ideal for fiscal and allocation metering. Eliminates the need to stack
multiple transmitters.

Model PX751T – Gage and Absolute Pressure Transmitter

measures absolute and gage pressures from 2,000 to 10,000 psi (13800 to 68900
kPa). The Model PX751T uses a single isolator design and microprocessor-based
electronics.

Reference Class

2

Pressure Transmitter

O to 2,000 psi (0.12–13800 kPa) with

2

O to 2,000 psig (0.62–13800 kPa) using

1-2

USING THIS MANUAL

This manual is designed to assist in basic installation and operation of Model PX751
Family of Smart Pressure Transmitters. For more detailed information, contact an
Omega product specialist.

Section 2 Commissioning

provides a description of common commissioning tasks.

Section 3 Installation

provides a flowchart outlining installation procedures and installation wiring
diagrams.

Section 4 Troubleshooting

provides basic troubleshooting techniques for common diagnostic messages
associated with the transmitter and the communicator.

Section 5 Reference Data

provides range tables, a typical model structure, and bolt torque specifications for
Model PX751 Transmitters.

Appendices

contain menu trees and fast key sequences for the HART Communicator.

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1-3

NEW FEATURES

The latest line of Omega Model PX751 pressure transmitters feature physical and

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software enhancements for additional functionality and increased ease of use.

Local Zero and Span Adjustments

•Simplified Push-Button Operation

Electronics Housing

•FOUNDATION™
Fieldbus Compatible

•More Space for Field Wiring

New Software Features

•Custom LCD Meter Units

•NAMUR Compliant Alarm and
Saturation Limits Available

Electronics Board

•“Plug-In” Shrouded Design

•Clear Labeling Simplifies Part
Identification

•Fully Backwards Compatible

Terminal Block

•3-Post Design Supports
External Meters

•Encapsulated Electronics for
Increased Robustness

•“Plug-In” Design for Easy
Installation

No Changes to the

Process Connections

Sensor Module

•Welded Metal Cap

•All Welded Design

•Fully Backwards Compatible

Optional LCD Meter

•2-line Display

•Capable of Displaying
Custom Flow, Level,
or Pressure Units

•Alarm and Security
Jumpers on Faceplate

3051-3031A08B, 3051LCD

1-4

SECTION

2

Commissioning

OVERVIEW

This section summarizes Model PX751 Transmitter commissioning procedures.

SAFETY MESSAGES

Procedures and instructions in this section may require special precautions to
ensure the safety of the personnel performing the operations. Information that raises
potential safety issues is indicated by a warning symbol (). Refer to the following
safety messages before performing an operation preceded by this symbol.

Warnings ( )

Explosions can result in death or serious injury.

•Do not remove the transmitter covers in explosive environments when the
circuit is alive.

•Both transmitter covers must be fully engaged to meet
explosion-proof requirements.

•Before connecting a communicator in an explosive atmosphere, make sure the
instruments in the loop are installed in accordance with intrinsically safe or
nonincendive field wiring practices.

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Electrical shock can result in death or serious injury.

•Avoid contact with the leads and the terminals. High voltage that may be present on
leads can cause electrical shock.

2-1

SETTING THE LOOP TO MANUAL

Whenever you are preparing to send or request data that would disrupt the loop or

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change the output of the transmitter, you will have to set your process application
loop to manual. The HART Communicator Model HC275
will prompt you to set the loop to manual when necessary. Keep in mind that
acknowledging this prompter does not set the loop to manual. It’s only a reminder;
you have to set the loop to manual yourself, as a separate operation.

FAST KEY SEQUENCES

For your convenience, fast key sequences are listed for common transmitter
functions. Complete tables of fast key sequences are located in Appendix A/
If you are unfamiliar with the communicator or how to follow fast key sequences,
please refer to Appendix A for communicator operations.

The fast key boxes in this section contain codes for the HART Communicator Model
HC275. From the Online menu (HART Communicator)
press these key sequences to access the desired transmitter function.

CONFIGURE THE ANALOG OUTPUT PARAMETERS

NOTE

The position of the transmitter security jumper may prevent configuration changes.
Refer to Section 5 for the proper placement of the transmitter security jumper.

Set the Process Variable Units

HART Comm.

The Model PX751 allows any of the following output units: inH2O, inHg, ftH2O,

2

mmH

O, mmHg, psi, bar, mbar, g/cm2, kg/cm2, Pa, kPa, torr, and atm.

1, 3, 2

2-2

Set the Output Type

HART Comm.

You can set the transmitter output to either linear or square root. Activate the
transmitter square root output mode to make the analog output proportional to flow.
While in square root output mode, the Model PX751 switches to linear output at 0.8%
of ranged pressure input, or 9% of full scale flow output to avoid the extremely high
gain that results as the input approaches zero. The transition from linear to square
root output is smooth, with no step change or discontinuity in output.

1, 3, 5

Rerange

The Range Values command sets the 4 and 20 mA points (lower and upper range
values). Setting the range values to the limits of expected readings maximizes
transmitter performance; the transmitter is most accurate when operated within the
expected pressure ranges for your application. In practice, you may reset the
transmitter range values as often as necessary to reflect changing process
conditions.

NOTE

Regardless of the range points, the Model PX751 will measure and report all readings
within the digital limits of the sensor. For example, if the 4 and 20 mA points are set
to 0 and 10 inH20, and the transmitter detects a pressure of 25 inH20, it digitally
outputs the 25 in H
may be up to ±5.0% error associated with output outside of the range points.

You may use one of three methods to rerange the transmitter. Each method is
unique; examine all three closely before deciding which method to use.

0 reading and a 250% percent of span reading. However, there

2

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2-3

Rerange with a Communicator Only

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HART Comm.

Reranging using only the communicator is the easiest and most popular way to
rerange the transmitter. This method changes the values of the analog 4 and 20 mA
points independently without a pressure input.

NOTE

Changing the lower or upper range point results in similar changes to the span.

NOTE

If the transmitter security jumper is in the “ON” position, you will not be able to
make adjustments to the zero and span. Refer to Figure 3-12 on Page 3-11 for the
appropriate placement of the transmitter security jumper.

4 -or- 5

Rerange with a Pressure Input Source and a Communicator

HART Comm.

Reranging using the communicator and a pressure source or process pressure is a
way of reranging the transmitter when specific 4 and 20 mA points are not known.
This method changes the values of the analog 4 and 20 mA points.

To rerange using the communicator and a pressure source or process pressure enter
the fast-key sequence above, select 2 Apply values, and follow the on-line
instructions.

1, 2, 3, 1, 2

NOTE

If the transmitter security jumper is in the “ON” position, you will not be able to
make adjustments to the zero and span. Refer to Figure 3-12 on Page 3-11 for the
appropriate placement of the transmitter security jumper.

2-4

Rerange with a Pressure Input Source and t he Local Zero and Span Buttons

Reranging using the local zero and span adjustments (see Figure 2-1), and a pressure
sour c e i s a w a y o f r e r a n g i n g t h e t ra n s m i t t e r when specific
4 and 20 mA points are not known and a c o m m u n i c a t or i s n o t av a i l a b l e .

NOTE

When you set the 4 mA point the span is maintained; when you set the 20 mA point
the span changes. If you set the lower range point to a value that causes the upper
range point to exceed the sensor limit, the upper range point is automatically set to
the sensor limit, and the span is adjusted accordingly.

To rerange the transmitter using the span and zero buttons, perform the
following procedure.

1. Loosen the screw holding the ce rtif ications l abel on t op of t he transmit t er
housing, and rotate the label to expose the zero and span buttons (see Figure
2-1 on page 2-5).

2. Using a pressure source with an accuracy three to ten times the desired
calibrated accuracy, apply a pressure equivalent to the lower range value to
the high side of the transmitter.

3. To set the 4 mA point, press and hold the zero button for at least two seconds,
then verify that the output is 4 mA. If a meter is installed, it will display
ZERO PASS.

4. Apply a pressure equivalent to the upper range value to the high side of the
transmitter.

5. To set the 20 mA point, press and hold the span button for at least two seconds,
then verify that the output is 20 mA. If a meter is installed, it will display
SPAN PASS.

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NOTE

If the transmitter security jumper is in the “ON” p osition, or if the local zero a nd spa n
adjustments are disabled through the software, you will not be able to make adjustments
to the z e r o and s pan u s i ng th e local buttons. Ref e r t o Figure 3-12 on Page 3-1 1 for the
proper placement of the transmitter security jumper. Or refer to “Local Span and Zero
Control” on page 2-6 for instructions on how to enable the span and zero buttons.

FIGURE 2-1. Local Zero and Span Adjustments.

Span and Zero Adjustment Bu tto ns

2-5

3051-3031D02A

Local Span and Zero Control

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HART Comm.

1, 4, 4, 1, 7

The Local keys command allows software control over the use of the local span and
zero adjustments. To enable or disable the span and zero adjustment buttons on your
transmitter, perform the fast key sequence above.

NOTE

Disabling the local keys only disables transmitter configuration changes using the
zero and span buttons. With the local keys disabled, you can still make changes to
the transmitter configuration using a Hart Communicator.

Set the Damping

HART Comm.

The Model PX751 electronic damping feature changes the response time of the
transmitter to smooth variations in output readings caused by rapid changes in
input. Determine the appropriate damping setting based on the necessary response
time, signal stability, and other requirements of the loop dynamics of your system.

1, 3, 6

LCD Meter Options

HART Comm.

1, 4, 3, 4

The Meter Options command allows you to customize the LCD meter for use in your
application. You can configure the meter to display the following information:

nEngineering Units
nPercent of Range
nUser-Configurable LCD Scale

(1)

nAlternating between any two of the above

The user-configurable scale (2 CM Setup) is a new feature that enables you to
configure the LCD meter to a custom scale using a Model HC275 HART communicator.
With this feature you can define the decimal point position, the upper range value,
the lower range value, the engineering units, and the transfer function. For more
detailed LCD meter information, contact an Omega product specialist.
.

(1) The user -configurable LCD scale is a feature specific to the new 4–20 mA output transmitters. It

is not available with Low Power transmitters.

2-6