Calibration Procedures; Thickness Mode Sub-Menu - NDT Systems Nova Eclipse TG930 User Manual

conditions, should be chosen. Pulse: toggles between Normal and Wide.
Normal is the default condition. At Pulse:, continue pressing the Down
Arrow key to toggle down through an array of setup parameters that are
User-selectable and adjustable.
Also within the Main Menu, the 2 Point CAL, ALARMS, and THICKNESS
MODE will be described in the Sections immediately following.

4.4 Calibration Procedures

With the Main Measurement display on, the NOVA TG930 is ready to be
calibrated for thickness measurement.
Single-Point Thickness Calibration: Couple the probe to an accurately
known thickness on an appropriate reference standard within the expected
thickness range. If necessary, refer back to Section 2.3, Reference
Standards. Scroll with the Up or Down ARROW keys until the display
precisely reads the reference thickness.
Two-Point Thickness Calibration: For maximum
accuracy over a range of expected thicknesses,
even under conditions where the test object has
smooth, parallel surfaces, two-point calibration
assures maximum accuracy. For some
applications, for example, smaller diameter tubing
or elbows, measurement accuracy also may be
improved with two-point calibration. However, it is necessary to have a
reference standard representative of the geometry to be measured. This
standard must have at least two accurately established thickness points.
(See Section 2.3, Reference Standards).
To access this option, press the MENU Touch Command to display the Main
Menu. With the Down ARROW, toggle down to 2 POINT CAL, and press
ENTER. A Measurement screen will be displayed similar to the one shown
above:
From this display, calibration on both high and low thicknesses can be
established. To use this calibration procedure, couple the probe to the low
thickness location on the reference standard, and use the Right and Left
ARROW keys to scroll Lo Thick to the known low thickness value.
Reposition the probe to the high thickness location, toggle down, and set Hi
Thick to the known high thickness. It may be necessary to repeat this
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Nova Eclipse TG930 - Users Manual
procedure until the precise thicknesses are set. Following two-point
calibration, press MENU to return to the Measurement Display.
Velocity Calibration: For the Velocity Measurement and Calibration
procedure, refer to Section 5.3, Ultrasonic Velocity.
As recommended with any precision measurement tool, calibration accuracy
should be checked periodically during use. More frequent checks are
recommended if there are changes in the temperature of the test object, or in
the ambient temperature.

4.5 THICKNESS MODE Sub-Menu:

Return to the Main Menu, toggle down to THICKNESS MODE, and press
ENTER. In this Sub-Menu, there are three choices: Normal, Diff., and
MinHold.
Normal: In this mode, when Normal is highlighted and ENTER is pressed,
the Measurement Display will open. Thickness readouts are presented and
held when the probe is removed from current measurement locations. If the
Scan Bar scale has been set, it will also be held and relate to the same
thicknesses.
Differential: In the Differential Thickness Mode, the difference between the
measured thickness and a pre-set, or nominal, thickness is displayed. To
set the thickness from which the difference will be displayed, ENTER
THICKNESS MODE from the Main Menu, and Diff. from the Sub-Menu. A
Measurement display opens. Immediately below the readout is a line
reading, Nom. :, followed by the value from a previous setting. The desired
Nominal thickness (Nom.) is set by using the Up and Down ARROW keys.
Press ENTER. Any thickness measurement taken thereafter will be
displayed as a value (+) or (−) from the Nominal setting.
An alternative way to set the nominal thickness value is to couple the probe
to a reliable reference standard. After a stable reading is obtained, press
ENTER.
To exit the Differential mode, return to the Main Menu, select THICKNESS
MODE, return the highlight to Normal, and press ENTER.
MinHold: Entering MinHold from the THICKNESS MODE Sub-Menu
provides for retention and display of the minimum thickness obtained during
a continuous scan across the surface of a test object.
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