GAOTek Digital ultrasonic flaw meter(master-slave menu)

Additional Information

Accessories:

Functions

Structure Feature

The Main Unit

Screen Display

The instrument displays are designed to be easy to interpret.

The Instrument has a digital screen for the display of A-Scan.
The status line below the wave display shows values of range settings and measured values.
On the first status line,

On the second status line, it shows the channel file name, the beam angle and the measured value of the peak echo inside the current selected gate.
“A →  61.3” means gate mode is single; current selected gate is gate A; and peak echo position: sound path 2.41 in (61.3 mm).
“AB → 24.0″ means the Echo-Echo mode of the gates; selected gate is gate A; sound path: 0.94 in (24.0 mm).The names of the menus or submenus are displayed at the bottom of the screen. The selected menu or submenu is highlighted.

Indicated at the right of the display, next to the A-Scan, are the functions of the corresponding menu.

The status area at the bottom-right corner shows the system status. The following status will be shown:

: Indicates the battery capacity
: Straight beam probe
: Angle beam probe
: Dual element probe
: Through-transmit mode
: Envelope function on
: Peak hold function on
   : A-Scan freezed

The status area at the top-right corner indicated shows the system gain and the sound velocity.

Keys and Rotary Knob Features

The instrument is designed to give the user quick access to all of the instrument’s functions. Its easy-to-use menu system allows any function to be accessed with no more than three key presses.
To access any function:

Special keys such as Gain, Gate, Range, Probe Zero-Offset Calibration, Angle Calibration, Freeze, Save Waveform, Auto-Gain, Envelop, Peak Hold and etc. are grouped together for easy thumb control. This design allows direct access to important instrument set-up parameters and provides easy and fast operating in difficult inspection environments.

Menus and Functions

The instrument menu system consists of several menus, submenus, and functions. It allows the operator to select and adjust various features and instrument settings.

Note that some functions, like RANGE, have both coarse and fine adjustment modes. There are three steps in the fine adjustment mode. Coarse and fine modes are selected by pressing the knob more than once. An icon of “” will appear on the left of the function name when the function is in fine adjustment mode. When the function is in coarse adjustment mode, turning the function knob will produce large changes in the selected function’s value. When the function is in fine adjustment mode, rotating the function knob will change the value by smaller amounts.

Alarm Lights

Two alarm lights appear at the top-right corner front of the instrument’s keypad. One alarm light is marked as ALARM, which is assigned to the gate alarm. When a gate alarm is triggered, this light will illuminate. The other light is marked as POWER indicating power and battery status.

Initial Start-up

Power Supply

The instrument can be operated with an external power adapter or with batteries. You can connect the instrument to the mains supply system even if it carries batteries. A discharged battery is charged in this case, via. parallel to the instrument operation.

Operation Using the Power Supply Unit

Connect the instrument to the mains socket-outlet using the power supply unit. The plug receptacle is at the top left of the instrument. Push the plug of the power supply unit into the plug receptacle until it snaps into place with a clearly audible click. The POWER LED on the keypad of the instrument will light in green color if the connection is properly aligned.

Operation Using Batteries

Use a lithium-ion battery pack provided with the instrument for the battery operation.

The battery compartment is situated at the instrument back. The lid is fastened with 4 attachment block. To insert the battery pack

Note:

The battery switch on the top of the instrument must be set to ON when operating with the battery pack or charging it.When not using the instrument, set the switch to OFF to save power.

Connecting a Probe

To prepare the instrument for operation, you have to connect a probe to it. The instrument is available with the probe connectors BNC (Lemo connectors are optional).

When connecting a probe to the instrument, it’s not only important that the probe’s physical connection be properly made. It’s also important that the instrument is properly configured to work with the installed probe. The instrument will operate with one or two single-element probes or with a dual-element probe.

To install a single-element probe, connect the probe cable to either of the two ports on the front of the instrument. When two probes or a dual-element probe is connected to the instrument, the “Receive” probe connector should be installed in the right port and the ‘Transmit’ probe connector in the left port.

Connect one single element probe to either port. Connect leads from a Dual Element Probe to both ports.

For through-transmission, connect two single element probes to the transmit and receive ports.

Starting the Instrument

To start the instrument, press the switch-on  . If it operates on the internal battery pack, make sure to set the battery switch to ON position before starting. The start display of the instrument appears; here you will also see the current software version and the serial number of the instrument. The instrument carries out a self-check and then switches over to stand-by mode.

The settings of all function values are the same as before switching-off of the instrument.The instrument will shut off automatically when the battery capacity level is too low.

Operation

Adjusting the Display Range

The function group BASE enables you to make the basic adjustment of the display range. The display on the screen must be adjusted for the material to be tested and for the probe used.

Calibration requires the use of calibrated standard made of the same material as the test piece. Prior to calibrating the instrument/probe combination, the A-Scan display-screen range (the material thickness value represented by the full horizontal width of the screen) will normally be set to a value equal to or slightly larger than the calibrated standard.

Setting the Material Velocity

Use VEL to set the sound velocity within the test object. Always ensure that the function VEL is correctly set. The instrument calculates all range and distance indications on the basis of the value adjusted here.

Velocity range：1000 m/s ~ 9999 m/s coarse adjustment, in steps as follows:

2260 m/s         2730 m/s         3080 m/s         3230 m/s

4700 m/s         5920 m/s         6300 m/s

Setting the Display Delay

Here you can choose whether to display the adjusted range starting from the surface of the test object, or in a section of the test object starting at a later point. This allows you to shift the complete screen display and consequently also the display zero. If the display should, for example, start from the surface of the test object, the value in D-DELAY must be set to 0. To set the display delay

D-DELAY range: -20 µs~3400 µs
Coarse adjustment: 12-pixel space (in µs) Fine adjustment: 1-pixel space (in µs)

Selecting the Probe Test Mode

You can use the function PROBE to activate the pulser-receiver separation. The following modes are available:

Auto Gain Feature

Use the Auto Gain function to automatically set the basic gain, so as to adjust the peak echo inside the current selected gate to a target height.

Configuring the Gates

The gates monitor the range of the test object where you expect to detect a flaw. If an echo exceeds or falls below the gate, an alarm signal is sent out via the ALARM LED. The gate chooses the echo for the digital time-of-flight or amplitude measurement.

The instrument has two gates: gate A and gate B. Gate A and B are independent of one another. Setting the position and characteristics of the A- and B-Gates is the first step to configuring the instrument for flaw detecting or material-thickness measurement. The GATE functions control not only the location of the A and B-Gates but also the alarms and other features activated when an A-Scan signal crosses a specific gate.

A-Scan signals crossing the A or B-Gate are evaluated for the purposes of flaw detection and material-thickness evaluation. When the signal crosses the A or B-Gate, the maximum point (peak) of the signal (in the specific gate) is used for evaluation purposes. The measured value is indicated on the status line.

Setting the Damping Level

This function serves for matching the probe. You can use it to adjust the damping of the probe’s oscillating circuit and to consequently change the height, width, and resolution of the echo display.

Setting the Damping Level

This function serves for matching the probe. You can use it to adjust the damping of the probe’s oscillating circuit and to consequently change the height, width, and resolution of the echo display.

Setting the Pulse Energy Level

Use the function ENERGY to set the pulser voltage. The relative energy with which the pulser fires can be set to LOW, MEDIUM or HIGH.The setting MEDIUM is recommended for most inspections. HIGH is used for inspections in which maximum sensitivity is the import, e.g. for the detection of small flaws. Choose the setting LOW for broadband probes or if narrow echoes are required (better lateral resolution).

To set the pulser energy

Adjusting the Pulse Repetition Frequency (PRF)

The pulse repetition frequency indicates the number of times an initial pulse is triggered per second. You can determine whether you need the highest possible PRF value, or whether you are satisfied with a low value.
The PRF value ranges from 10 Hz to 1000 KHz. The larger your work piece, the smaller PRF values are needed in order to avoid phantom echoes. In the case of smaller PRF values, however, the A-Scan update rate becomes lower, for this reason, high values are required if a work piece should be scanned fast.
The best way to determine the suitable PRF value is by experimenting: start from the highest step and reduce the value until there are no more phantom echoes.

To set the PRF level

Specifying the Probe Frequency

In this function, you can specify the probe frequency according to the frequency of your probe. The instrument will automatically utilize a built-in filter to match the probe frequency.

Setting the Probe X-Value

The function X-VALUE enables you to set the X-Value (distance between the probe’s leading face and probe index/sound exit point) of the probe used. This value is required for the automatic calculation of the reduced projection distance in angle beam transducer operation.
Adjustment range: 0 in~1.96 in (0 mm~50 mm)

Connecting to a Computer

The instrument is equipped with a USB port at the upper left of the instrument. The PC can be connected to the instrument via the USB port. A-Scan display, instrument settings, and videos stored in the memory of the instrument can be transferred to the computer through the USB port.

Calibration and Measurement

Before working with the instrument, you have to calibrate the instrument: you have to adjust the material velocity and display range and allow for the probe delay depending on the material and dimensions of the test object.To ensure a safe and proper operation of the instrument, it is necessary that the operator is adequately trained in the field of ultrasonic testing technology.
Below you will find some examples of common calibration methods for certain test tasks.

Calibration with Straight- and Angle-Beam Probes

Case A: With Known Material Velocity Calibration process

Case B: With Unknown Material Velocity

Use the semiautomatic calibration function of the instrument via the function group CAL for this calibration case.

The distances between two calibration echoes must be entered. The instrument will then carry out a plausibility check, calculate the material velocity and the probe delay, and automatically set the parameters using the calculation result.

Calibration Process

Set the required display range in RANGE. The two calibration echoes selected must be displayed on the screen. Set the range so that the second calibration echo is located on the right edge of the screen.

Example:

You are carrying out the calibration with a straight probe for the calibration range of 11.81 in (300 mm)

Calibration with Dual-Element (TR) Probes

Dual-element (TR) probes are especially used for wall thickness measurement. The following peculiarities must be taken into account when using these probes:

Echo Flank: Most dual-element (TR) probes have a roof angle (transducer elements with an inclined orientation toward the test surface). This causes mode conversions both at beam index (sound entry into the material) and at the reflection from the back wall, which can result in very jagged echoes.

V-Path Error: Dual-element (TR) probes produce a v-shaped sound path from the pulser via the reflection from the back wall to the receiver element. This so-called “V-path error” affects the measuring accuracy. You should, therefore, choose two wall thicknesses that cover the expected thickness measurement range for the calibration. In this way, the V-path error can be corrected to the greatest possible extent.

Calibration Process

We recommend using the semiautomatic calibration function for the calibration with T/R probes.

Distance Amplitude Curve

The instrument is available with Multi-Curve Distance Amplitude Curve (DAC) function. Functions for the distance-amplitude curve are accessed through the DAC Menu, which is located by pressing .

When displayed, the DAC curve visually represents a line of constant reflector peaks over a range of material depths. A new feature of the instrument is a multiple-curve option that displays three dB offset DAC curves simultaneously. Each curve represents constant reflector size at varying material depth. Remember that in DAC mode, the only deviation from traditional display and operation is the appearance of the DAC curve. All A-Scan echoes are displayed at their non-compensated height.

A DAC curve is programmed using a series of same-reflector echoes at various depths covering the range of depths to be inspected in the test material. Because near field and beam spread vary according to transducer size and frequency, and materials vary in attenuation and velocity, DAC must be programmed differently for different applications. A DAC curve can be based on up to 16 data points (material depths).

Measuring with DGS/AVG

Using the AVG (the same as DGS) function, you can compare the reflecting power of a natural flaw in the test object with that of a theoretical flaw (circular disk-shaped equivalent reflector) at the same depth.
Note: You are comparing the reflecting power of a natural flaw with that of a theoretical flaw. No definite conclusions may be drawn on the natural flaw (roughness, inclined position, etc.).The so-called AVG diagram forms the basis for this comparison of the reflecting power. This diagram consists of a set of curves showing the correlation of three influencing variables:

The advantage of the AVG method lies in the fact that you can carry out reproducible evaluations of small discontinuities. The reproducibility is most of all important, for example, whenever you aim to carry out an acceptance test.Apart from the influencing variables already mentioned, there are other factors determining the curve shape: sound attenuation, transfer losses, amplitude correction value, probe etc.

The following probe parameters affect the curve shape:

You can adjust these parameters on the instrument in such a way that you can use the AVG method with many different probes and on different materials.

Note: Before setting the AVG function, the instrument must first be calibrated because all functions affecting the AVG evaluation mode (VEL, P-DELAY, DAMPING, ENERGY, P-WIDTH, FREQ, DIAMETER, RECTIFY) can no longer be changed after the reference echo has been recorded.

Curved Surface Correction

When using angle beam transducers on a curved surface, the instrument will calculate the surface distance and depth of defect, taking into account the internal or external radius.

THICK: Use the THICK function to set the material’s wall thickness. This value is required for the automatic calculation of the real depth.
Adjustment range: 0 in~196.85 in (0 mm~5000 mm)

O-DIAM (Outside diameter of the test object): You will need the CSC function for tests on circular curved surfaces, for example when testing longitudinally welded tubes. In order to make the instrument carry out the corresponding correction of (reduced) projection distance and depth, you should enter the outside diameter of your test object in this function.
Adjustment range: 0 in~196.85 in (0 mm~5000 mm)

CSC: If you plan to carry out the flaw position calculation for the curved surface workpieces, the CSC function should be turned on. Otherwise turn off the CSC function.

Crack Height Measuring Feature

This feature allows measuring the height of a crack found inside the workpiece. Before starting to use the Crack Height Measure function, the instrument and the probe must be correctly calibrated.

Data Storage

The instrument is equipped with a data-storage system. A-Scans patterns, instrument settings, and video can be stored in data files for later retrieval. File data can be saved, recalled and deleted by using the MEM menu.

Wave Files

Wave files are used to store A-Scan pattern, along with the instrument settings. Data in the wave files can be stored, recalled and erased.

Wave STORE

You can save the A-Scan pattern to a wave file using the STORE function.

Note:

The asterisk (*) before a selected file name indicates that this file is already occupied. It is not possible to overwrite an occupied file. Users should select another file name which is still empty or clear the occupied file to save to. To avoid loss of data e.g. in case of a software update you should save the file to a PC.

Wave RECALL

You can recall a stored wave file; your instrument will then display all the test-relevant technical features that existed at the moment of the setup. A frozen display of the stored A-Scan appears.

Wave CLEAR

An occupied file is marked with an asterisk (*) before the file name. You can clear the file if you no longer need them. Wave Files are cleared using the CLEAR function.

Channel Files

Channel files (CH00~CH99) are used to store a specific instrument setup configuration. This means that whenever you recall a stored channel file, your instrument is again set up exactly the same as it was at the moment when the file was stored. This makes each one of your tests reproducible. You will find the following functions:

Channel STORE

To store instrument settings in a channel file follow this procedure

Note that if the channel file is not empty, it will prompt out to ask if you want to overwrite the channel file.

Channel COPY

To copy instrument settings from another channel file to this channel,

Channel CLEAR:

Channel files are cleared using this procedure:

Note:

The cleared file may not be retrieved.
The current settings of the instrument will be reset to default settings after the channel clear operation.

Video Files

Video file (DV01) is used to store a segment of the video. To record a segment of video
– Activate the video recording operation by pressing  . An icon will appear in the status area when recording the video.
– To stop the recording, simply press  once more.
The recording process will automatically end when the video file is full. Use RECALL function to RECALL a video file.

RESET Function

You can clear all channels, all waves and all videos using the functions in the RESET submenu.