ElektroPhysik MiniTest 430, MiniTest 440 Technical Manual And Operating Instructions

Technical Manual and

Operating Instructions

Ultrasonic Thickness Gauges

MiniTest 430 / 440

Important Note

In ultrasonic thickness measurement it is inherent to the measuring procedure that the gauge might
use the second echo rather than the first one reflected from the material being measured. This may
result in a thickness reading TWICE as high than the actual thickness.
When measuring through extremely thick coatings in the echo-echo mode, it may occur that the
thickness of coating layer is measured instead of the wall thickness that actually was intended to
be measured.

The responsibility for proper use of the gauge and recognition of this phenomenon rests solely with
the user of the gauge.

© Editon 1, 08/2014

Version 1.0

Subject to change without notice.
ElektroPhysik

Dr. Steingroever GmbH & Co. KG
Pasteurstr. 15
50735 Koeln, Germany

Phone: [phone]
Fax : [phone]
Internet: http://www.elektrophysik.com/
Mail: [e-mail]

Table of Contents

1. Introduction ............................................................................................................................... 5

1.1 Important Notes on Wall Thickness Measurement ................................................................ 5

Prerequisites for the use of ultrasonic wall thickness gauges ................................................. 5

1.1.1 Training of the Person in Charge of Testing .................................................................. 6

1.1.2 Limitations to Ultrasonic Testing.................................................................................... 6

1.1.2.1 Ultrasonic Wall Thickness Testing ........................................................................... 6

1.1.2.2 Influence of the Material to be tested ....................................................................... 7

1.1.2.3 Influence of Changes in Temperature ...................................................................... 7

1.1.2.4 Measurement of the Residual Wall Thickness ......................................................... 7

1.1.2.5 How to use the Couplant ......................................................................................... 7

1.1.2.6 Duplication of Reading ............................................................................................. 8

2. Technical Specifications .......................................................................................................... 9

3. Measuring Principle ................................................................................................................ 10

4. Description of the Gauge and Schedule of Supply ............................................................... 11

4.1 Description of the Gauge (Front and back Side) .................................................................. 11

4.2 Supply Schedule ................................................................................................................. 11

4.2 Display ................................................................................................................................ 12

4.3 Keyboard ............................................................................................................................. 13

5. Preparing Measurement ......................................................................................................... 14

5.1 Preparing the Gauge ........................................................................................................... 14

5.2 Selection of the Transducer ................................................................................................. 14

5.3 Preparing the Surface of Measuring Object ......................................................................... 15

6. Operation ................................................................................................................................. 16

6.1 Switch ON ........................................................................................................................... 16

6.2 Taking Readings ................................................................................................................. 16

6.3 Calibration ........................................................................................................................... 17

6.3.1 Calibration ................................................................................................................... 17

How to calibrate MiniTest 430 / 440 ................................................................................... 17

6.3.2 Determination of the Sound Velocity ........................................................................... 17

6.3.2.1 How to determine the Sound Velocity....................................................................... 18

6.3.3 Calibration of the Transducer.................................................................................... 18

6.4 User Menu .......................................................................................................................... 19

6.4.1 Measuring Mode (Meas. Mode) .................................................................................. 19

6.4.1.1 MiniTest 430 .......................................................................................................... 19

6.4.1.2 Operating modes of MiniTest 440 .......................................................................... 21

6.4.1.2.1 I-E mode ............................................................................................................. 21

6.4.1.3.2 Echo-Echo mode ................................................................................................ 22

6.4.2 Sound Velocity ............................................................................................................ 23

6.4.2.1 Materials ................................................................................................................ 23

6.4.2.2 Setting Sound Velocity (vel. custom) ..................................................................... 24

6.4.3 Measuring Unit ............................................................................................................ 25

6.4.4. Data Memory ............................................................................................................. 25

6.4.4.1 Select a Batch (MiniTest 430 / 440) ....................................................................... 26

6.4.4.2 Delete a Batch (MiniTest 430 / 440) ....................................................................... 26

6.4.5 Gain Setting ................................................................................................................ 27

6.4.6 Switch Off Mode .......................................................................................................... 27

6.4.7 Contrast ...................................................................................................................... 28

6.4.8 Language .................................................................................................................... 28

6.4.9 Gauge Data ................................................................................................................ 28

6.4.10 Standard Setting ....................................................................................................... 28

6.5 Data Processing .................................................................................................................. 28

6.6 Storing Readings ................................................................................................................. 28

7. Measuring Technology ........................................................................................................... 29

7.1 Measuring Methods ............................................................................................................. 29

7.2 Measurement on Pipes and Tubes ...................................................................................... 29

8. Maintenance and Precautions ................................................................................................ 30

8.1 Power Check ....................................................................................................................... 30

8.2 Precautions ......................................................................................................................... 30

8.2.1 General Precautions ................................................................................................... 30

8.2.2 Precautions to take during Measurement .................................................................... 30

9. Table of Materials and their typical Sound Velocity (Longitudinal Wave) ..................... 31

10. Safety Notes .......................................................................................................................... 32

11. Declaration of Conformity .................................................................................................... 33

11. After-Sales Service ............................................................................................................... 33

13. Change History ..................................................................................................................... 33

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1. Introduction

The MiniTest 420 and 440 model are non-destructive ultrasonic thickness gauges for portable or
stationary use. Working according to the ultrasonic principle it enables quick and easy measurement
of wall thickness. It can also be used for the measurement of the sound velocity of metals and various
other materials.

Prior to use, please read the operating instructions carefully in order to get familiar with the use
and all functionalities of the MiniTest 430/440 gauges.

Even if you are already familiar with measurement according to the ultrasonic principle, it is highly
recommended to read section 1.1 carefully. This section provides important information on the
limitations to and conditions for reliable wall thickness measurement such as technical training,
required knowledge on the specific requirements for testing and the selection of a suitable test
equipment.

The gauge is easy to use. To enable its quick use, please read the sections below to get familiar
with the preparatory requirements and basic functions.

1.1 Important Notes on Wall Thickness Measurement

Before using the wall thickness gauge, please read the following instructions
carefully. Make sure to fully understand and follow the instructions in order to
avoid errors that might lead to erratic readings. Any decisions based on erratic
readings may cause damage to property or personal injury.

Prerequisites for the use of ultrasonic wall thickness gauges

This manual contains essential information on how to operate your measurement device. In
addition, there are a number of other factors to influence measurement. A detailed description of all
such factors would be beyond the scope of this manual. For that reason, this manual is limited to
the three most important requirements for reliable ultrasonic wall thickness measurement:

 adequate training of the person in charge of measurement
 fundamental knowledge on the specific requirements on and limitations to the measuring

technique used for testing

 choice of a suitable measuring equipment

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1.1.1 Training of the Person in Charge of Testing

The proper use of ultrasonic test equipment requires an adequate training in the field of ultrasonic
wall thickness testing. Such training should include the following subjects:

 theory of sound propagation in materials
 effect of the sound velocity inherent to material to be tested
 behaviour of sound waves at the interfaces between different materials
 propagation of the sound beam in the material
 effect of the surface quality of the material to be tested

Insufficient knowledge on the above topics may result in erratic readings and thus lead to
unforeseen consequences. For more information on the availability of training opportunities for
examiners in ultrasonic testing, qualifications and certificates, please contact your national NDT
partner, or, in Germany Deutschen Gesellschaft für Zerstörungsfreie Prüfung e.V., Motardstraße
54, D-13629 Berlin.

1.1.2 Limitations to Ultrasonic Testing

The results obtained from measurement solely relate to areas of the measuring object that have
been targeted by the sound beam. Conclusions to other areas of the measurement object are not
admissible. They are only allowed if extensive experience on the process of manufacture of the
measuring objects is available and if appropriate methods of statistical evaluation can be applied.
It should be taken into consideration that the ultrasound beam might be completely reflected by
interfaces being present in the measuring object so that deeper reflection points will not be
reached by the ultrasound any more. For that reason it must be ensured that all areas of the
measuring objects to be measured can be reached by the sound beam.

1.1.2.1 Ultrasonic Wall Thickness Testing

Ultrasonic wall thickness measurement is based on the measurement of travel times of sound
pulses in the object to be measured. For reliable wall thickness measurement it is presumed on the
assumption that the velocity in the measuring object remains constant. Generally, this is given for
the majority of work-pieces made of steel. Even if they include different alloy components, the
sound velocity changes will be small enough to be neglected (unless high-precision measurement
is required).

7

In other materials such as non-ferrous metals or plastics, the sound velocities are subject to major
changes that might impair the measuring accuracy.

1.1.2.2 Influence of the Material to be tested

Material discontinuities may lead to strong variations of the sound velocity within a measuring
object. In such case, an average sound velocity should be used for testing.
However, the best results will obtained when calibrating the gauge by means of a reference
sample. This sample must be made of the same material as the object to be measured and should
exhibit plane parallel surfaces. Its thickness should equal the maximum thickness of the later
object to be measured. Please note that any heat treatment might considerably change the sound
velocity and thus influence the measuring precision accordingly.
If dramatic changes of the sound velocity are to be expected, it is recommended to readjust the
sound velocity within shorter time intervals. This is to avoid erratic readings.

1.1.2.3 Influence of Changes in Temperature

The sound velocity is also influenced by the temperature prevailing in the material. If the gauge has
been adjusted to a “cold” reference sample and wall thickness measurement is made on a “warm”
object, major measuring errors are very likely to occur.
To avoid such measuring errors, it is recommended to use a temperature-adapted reference
sample for adjusting the gauge. Another option would be to correct for the applicable temperature
influence by means of the sound velocity/temperature correction table.

1.1.2.4 Measurement of the Residual Wall Thickness

Measuring the residual wall thickness of internally eroded or corroded objects such as tubes,
containers or reaction vessels makes it necessary to choose a most suitable test equipment and to
handle the sensor with utmost care. In addition, the nominal wall thickness as well as the
suspected degree of wall thickness loss should be known.

1.1.2.5 How to use the Couplant

Make sure the user is familiar with the use of couplant. For each measurement, the couplant must
be applied evenly over the surface of the measuring object. Any variations in couplant layer thickness
will influence measuring accuracy. Both, adjustment of the gauge and wall thickness measurement
must be made under the same coupling conditions. Make sure to use a quantity of couplant as small
as possible and to apply a constant contact pressure of the sensor.

8

When measuring on curved surfaces such as pipes or tubes make sure the coupling of the
transceiver is made properly. The acoustic layer interface of the transceiver must be aligned so as
to form a right angle to the axis of curvature of sample (longitudinal axis of tube). For small tube
diameters it is recommended to carry out two measurements: one with the layer interface in vertical
position to the longitudinal axis of tube, another one in parallel position to the longitudinal axis of
tube. The smaller of the two readings obtained should be used as the correct one for this measuring
spot.

(senkrecht = vertical)

1.1.2.6 Duplication of Reading

Do not measure in a range lower than the measuring range specified for the sensor. In such case,
the first back wall echo would not be strong enough for being processed whereas the amplitude of
the second one would be strong enough to be processed accordingly. As a result, the reading
obtained would be twice the actual wall thickness. In order to avoid such errors when measuring at
the limit of the measuring range it is recommended to verify results by using another sensor.
In critical cases, it is recommended to use display screen equipment to provide additional information
on the echo curve.

.

9

2. Technical Specifications

Display screen: 128 x 64 pixel dot matrix LC display, backlit
Digital display: four-digits
Measuring range: 0.65 mm ... 500.0 mm (steel) depending on transducer

Display resolution:

0.1 mm (if readings > 100 mm)

0.01 mm (if readings < 100 mm)

Measuring accuracy:

0.65 mm... 9.99 mm: ± 0.04 mm
10 mm… 99.99 mm: ± (0.04 mm + 0.1% of reading)

100 mm... 500 mm: ± (0.3 % of reading)
Sound velocity: 1000...9999 m/s
Data memory: 10 batches for a maximum of 500 readings per batch

Measuring frequency:

2 readings/second in the standard mode

10 readings/second in the high-performance mode (scan)
Zero point calibration: automatic
Auto switch-off: 2 minutes, 5 minutes or shut down manually
Power supply: 2 x AA battery, battery life 80 h in continuous operation
Operating temperature: -20°C ... 50°C
Storage temperature: -25°C ... 60°C
Dimensions: 130 x 73 x 24 mm
Weight: 190 g (without batteries)
Options Transducers U2.0, U5.0, U7.5, U10.0, U5.0HT

10

3. Measuring Principle

The ultrasonic sensor head emits an ultrasonic signal to travel through the sensor head, the
couplant and finally to the measuring object. A portion of the ultrasound signal is reflected from the
surface of measuring object, another one is reflected from the opposite side of the object when
travelling back. The sensor receives both echoes. The wall thickness is calculated according to the
exact time of travel of pulse and shown as reading on display.