Chapter 4. Measuring and Recording Data

Chapter 4. Measuring and Recording Data

This chapter will explain how to measure thicknesses and store those measurements in the data file you have created in Chapter 3. If you wish to store the measurement data and have not yet created a data file, refer to Chapter 3.

4.1

Setting up Data Measurements

4.1.1

Positioning Gate A and Gate B

Setting the position and the characteristics of Gate A and Gate B is the first step in configuring the instrument for material thickness measurements. Use the procedures in this section to set the vertical and horizontal position of Gate A and Gate B. Remember that gate position has the following effects on instrument performance:

•

A-Scan echoes on the right side of the display screen represent features that occur at a greater depth from the test-material surface than those on the left side of the display screen. Therefore, moving a gate to the right means that the gate is evaluating a deeper portion of the test material.

•

A wider gate setting means that the gate is evaluating a thicker portion of the test material.

•

Increasing the vertical height, called the threshold, of a gate means that only reflected signals of sufficiently large amplitude will cross the gate.

Each probe selected has default gate settings which should work for most applications. If the echoes are not being properly measured, the user can adjust the gating to ensure the DMS Go is measuring the proper echoes. To configure the gate parameters, proceed to the appropriate section:

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Chapter 4. Measuring and Recording Data

4.1.1a Setting the Gate Starting Point (GATE - GATE A or GATE B START)

1.

In the

MAIN menu, scroll to the GATE submenu using the joystick (

).

2.

Use the joystick ( ) to select the

GATE A START (or GATE B START) function.

3.

To change the gate starting point, either move the joystick ( ) or press F3 and F4.

Increasing and decreasing the value of the starting point moves the gate to the right and left, respectively. The gate starting point remains as set here, even when width adjustments are made.

Note: The GATE A START and GATE B START functions have both coarse and fine adjustment modes. Coarse adjustments (of .050,.060 or

,100 increments) are made with the function toggle, while fine adjustments (of 0.001 in) are made with the joystick. When the function name appears in all capital letters, coarse adjustments are being made, while fine adjustments occur when the function name appears in all lower-case letters.

4.

After completing your selection, move the joystick up or down ( to the Main Menu.

) to navigate away from this function, or press

HOME to return

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Chapter 4. Measuring and Recording Data

4.1.1b Adjusting the Gate Width (GATE - GATE A WIDTH or GATE B WIDTH)

Adjusting the A-gate width may be necessary in multi-echo modes because the returning sound pulse (backwall echo) may be too low in amplitude to trigger a measurement reading. Adjusting the B-gate width reduces or increases the width of the B-gate to control which signal crosses the B-gate and triggers a thickness measurement.

1.

In the

MAIN menu, scroll to the GATE submenu using the joystick (

).

2.

Use the joystick ( ) to select the

GATE A WIDTH (or GATE B WIDTH) function.

3.

To change the gate width, move the joystick ( ) or press the function toggle.

Note: The GATE A WIDTH and GATE B WIDTH functions have both coarse and fine adjustment modes. Coarse adjustments (of 1,5 or 10 in)

are made with the function toggle, while fine adjustments (of 0.001 in) are made with the joystick. When the function name appears in all capital letters, coarse adjustments are being made, while fine adjustments occur when the function name appears in all lower-case letters.

4.

After completing your selection, move the joystick up or down ( return to the Main Menu.

) to navigate away from this function, or press HOME to

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4.1.1c Setting the Gate Threshold (Vertical Position) (GATE - GATE A THR or B THR)

1.

In the

MAIN menu, scroll to the GATE submenu using the joystick (

).

2.

Use the joystick ( ) to select the

GATE A THR (or B THR) function.

3.

To change the gate height, either move the joystick ( ) or press the function toggle. Increasing or decreasing the value of the threshold moves the gate up or down, respectively.

4.

After completing your selection, move the joystick up or down ( ) to navigate away from this function.

Note: When RECTIFY is RF, negative threshold values are available.When changed to POS, NEG or FULL, the gate threshold changes to

the corresponding positive values for a short period of time. However, when RECTIFY is switched back to RF, negative positions for

GATE THRESHOLD(s) may be reinstituted again.

Gate B is not permanently available; it is available in TG MODE S-PEAK, S-FLANK for single element probes, and in DUAL

MULTI for some dual element probes.

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