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Module - Dpe

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    MODULE - DPE

    MODULE DPE

    DIFFERENTIAL PRESSURE MEASUREMENT ELECTRONIC METHODS

    OBJECTIVE

    On completion of this module you will be required to:-

    a) Identify and name all parts of an electronic D/P Cell.

    b) Calibrate an Electronic D/P Cell for an output of 4mA to 20mA.

    RESOURCES:

    1.) Your training Officer

    2.) Your Module DPE

    Instrumentation : Document No. 10 Page 1 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE DPE

    DIFFERENTIAL PRESSURE MEASUREMENT ELECTRONIC METHODS

    CONTENTS PAGE

    1.) INTRODUCTION PAGE 3

    2.) PRINCIPLE OF OPERATION PAGE 3

    3.) COMPONENT NAMES PAGE - 4

    4.) PRECAUTIONS PAGE 5

    5.) INSTALLATIONS PAGE 6

    6.) CALIBRATION PAGE 7

    7.) SELF TEST PAGE 10

    Instrumentation : Document No. 10 Page 2 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    MODULE DPE

    DIFFERENTIAL PRESSURE MEASUREMENT ELECTRONIC METHODS

    INTRODUCTION

    The Electronic D/P Cell is an instrument that continuously measures Differential

    Pressure and transmits this measurement as a Proportional Current output signal

    ranging between 4mA and 20mA.

    The Differential Pressure Cell is a versatile instrument and is used in Flow, Liquid

    Level and other Differential Pressure applications.

    PRINCIPLE OF OPERATION

    The Electronic D/P Cell consist of two major assemblies, one is the Topworks

    Housing, which encloses the electronics module in one compartment and the

    Field Termination Block in the other compartment.

    The other major assembly includes the sensor assembly and the process covers

    and is known as the pressure-detector section.

    The high and low pressures are connected to opposite sides of the pressure-

    detector section.

    The resulting Differential Pressure in then converted to a proportional 4mA to

    20mA output signal. Different manufacturers of Electronic D/P Cells use different

    technologies to measure and convert the differential signals to the 4mA to 20mA

    signal.The electronic signal is transmitted to a receiving instrument to record, indicate

    and / or control.

    Instrumentation : Document No. 10 Page 3 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    COMPONENT NAMES

    Figure 1

    A. FIELD TERMINATION SIDE

    A. ELECTRONICS SIDE

    Instrumentation : Document No. 10 Page 4 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    B. SEAL

    C. - ELECTRONICS MODULE

    D. - SENSOR ASSEMBLY

    E. - PROCESS COVER

    F. - PROCESS SIGNAL LINE CONNECTION

    G. PROCESS COVER GASKET

    PRECAUTIONS

    1. During draining condensate of venting gas from the transmitter

    pressure-detector section, take appropriate care to avoid contact

    with the skin, eyes or body, or inhalation of vapors, the process

    fluids or gasses may be toxic or harmful. Since draining condensate

    of bleeding off of gas gives the pressure measurement a

    disturbance, these operations should not be performed when the

    loop is in operation.

    2. If the process fluid or gas is toxic or harmful, take appropriate care

    to avoid contact with the skin, eyes or body, or inhalation of vapors

    when removing the instrument for maintenance.

    3. As a general rule, maintenance to this device should only carried

    out in a maintenance workshop that is equipped with the necessary

    tools and equipment.

    Instrumentation : Document No. 10 Page 5 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    4. Handling the CPU assembly. The CPU assembly contains

    sensitive components that may be damaged by static electricity.

    Take care not to touch the electronic components, electrical

    contacts or printed circuit board patterns on the board.

    It is best to use a grounded wrist strap assembly to avoid damage

    caused by static electricity.

    Always place the electronic module in a special plastic bag with an

    antistatic coating when removing and transporting the module.

    Note: CPU stands for Central Processor Unit

    TYPICAL D/P CELL INSTALLATIONS

    Instrumentation : Document No. 10 Page 6 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    FIGURE - 3

    Liquid level measurement in an open tank

    Instrumentation : Document No. 10 Page 7 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    FIGURE 4

    Liquid level measurement in an closed tank

    Instrumentation : Document No. 10 Page 8 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    CALIBRATION

    1. Connecting the Process input signal to the D/P Cell. Refer to Fig.

    5. A typical process input signal would be 0 Kpa to 30 Kpa. This value

    will however be determined by the actual application where the D/P

    Cell is to be used.

    Symbols H and L are shown on the capsule assembly to indicate

    the high and low pressure connections on the capsule of the D/P Cell.

    For calibration purposes, you must connect the pressure input signal to

    the H side connection of the capsule.

    FIGURE 5

    Instrumentation : Document No. 10 Page 9 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    2. Wiring the D/P Cell for Calibration. Connect a 24 VDC power supply

    to the D/P Cell as shown in Figure 6

    POWER SUPPLY WIRING CONNECTION

    Connect the power supply wiring to the SUPPLY + and - terminals

    FIGURE 6

    Instrumentation : Document No. 10 Page 10 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    Connect a Milliamp Meter as shown in Figure 7 or in series with the

    positive supply lead as shown in Figure 8

    FIGURE - 7

    Instrumentation : Document No. 10 Page 11 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    FITGURE 8

    CALIBRATION PROCEDURE

    1. With no differential pressure applied to the capsule, adjust the

    ZERO screw until a value of 4mA is displayed on the milliamp

    meter.

    2. Apply a regulated pressure equivalent to the upper range value to

    the high-pressure connection. eg. 30 Kpa.

    3. Adjust the SPAN screw until the output displayed on the milliamp

    meter is 20 mA.

    Instrumentation : Document No. 10 Page 12 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    4. Repeat steps 1, 2 and 3 until the ZERO and Upper Range values

    are 4 mA and 20 mA respectively.

    When you have completed the calibration, you must ask the Training Officer to

    check your work.

    If you have attained the required standard, you may proceed with the Criterion

    Test.

    Instrumentation : Document No. 10 Page 13 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    MODULE DPE

    DIFFERENTIAL PRESSURE MEASUREMENT ELECTRONICMETHODS

    SELF TEST:

    QUESTION 1

    Blank out the bottom of Page 4 Figure 1 and name all of the componets of

    the D/P Cell

    QUESTION 2

    Calibrate the D/P Cell supplied to you for a range of 0 Kpa to 50 Kpa.

    LEARNER TRAINING OFFICER

    DATE:

    SIGNED:

    DATE:

    SIGNED:

    Instrumentation : Document No. 10 Page 14 of 17

    Created : 01 February 2003 Revision No: 01

    Last Approved : March 2003 First Published : March 2003

    Revised : Owner: Learnership Dept.

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    MODULE - DPE

    DPE

    CRITERION TEST

    DIFFERENTIAL PRESSURE CELL ELECTRONIC

    NAME

    DATE

    COMPANY NUMBER

    SIGNATURE

    ASSESSOR SIGNAT

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