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8/22/2019 Module - Dpe http://slidepdf.com/reader/full/module-dpe 1/17 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) Calibr ate 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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Page 1: Module - Dpe

8/22/2019 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) Calibr ate 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.

Page 2: Module - Dpe

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MODULE - DPE

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 SIGNATURE

RESULT COMPETENT / NOT YET COMPETENT

Instrumentation : Document No. 10 Page 15 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

QUESTION – 1

Label the attached diagram of an Electronic D/P Cell

Instrumentation : Document No. 10 Page 16 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

QUESTION – 2

State the standard supply voltage for an Electronic D/P Cell

 

QUESTION – 3

State the standard output signal for an Electronic D/P Cell

 

Question – 4

Calibrate and Electronic Cell for a Range of 0 Kpa to 40 Kpa

Instrumentation : Document No. 10 Page 17 of 17

Created : 01 February 2003 Revision No: 01

Last Approved : March 2003 First Published : March 2003

R i d O L hi D t