DMTA-10004-01EN, Rev. D, November 2016
Chapter 10
156
10.7 Using Temperature Compensation
The 38DL PLUS can compensate for changes in sound velocity due to temperature
variations. This function is useful for example when the test block may be at room
temperature while the actual material can be at an elevated temperature.
Using the temperature compensation function, you can input the temperature of the
calibration standard in °F or °C units. You can manually enter a fixed elevated
temperature, manually enter a temperature for the current ID location, or
automatically read the temperature from an optional temperature probe.
The sound velocity of most steel changes about 1 % for every 55 °C (100 °F) change in
temperature. The following equation is used to compensate for the change in sound
velocity due to temperature.
Where:
MTI = Measured time interval
V
0
= Calibrated test block velocity
T
1
= Actual material temperature
T
0
= Temperature at calibration
k = Temperature coefficient (normally –0.00018 for °C or –0.0001 for °F)
A temperature coefficient of 0.00018 for °C (or 0.0001 for °F) assumes a 1 % change in
velocity per 55 °C (100 °F) change in temperature.
To use the temperature compensation
1.
Press
[SETUP MENU]
.
2.
In the menu, select the
TEMP COMP
.
3.
In the
TEMP COMP
screen (see Figure 10-18 on page 157):
a)
Set
TEMP COMP ENABLE
to
ON
to activate the temperature compensation
function.
b)
Set
DEGREE UNITS
to the desired temperature units (
FAHRENHEIT
or
CELSIUS
).
c)
Set
CALIBRATION TEMP
to the temperature of the test block used to
perform the calibration. The allowable range is –10 °C to 500 °C or 14 °F to
932 °F.
Temperature corrected thickness
MTI V
0
×
1
k
T
1
T
0
–
(
)
×
(
)
+
(
)
×
=
Summary of Contents for 38DL PLUS
Page 9: ...DMTA 10004 01EN Rev D November 2016 Table of Contents ix Index 297 ...
Page 10: ...DMTA 10004 01EN Rev D November 2016 Table of Contents x ...
Page 28: ...DMTA 10004 01EN Rev D November 2016 Important Information Please Read Before Use 16 ...
Page 30: ...DMTA 10004 01EN Rev D November 2016 Introduction 18 ...
Page 50: ...DMTA 10004 01EN Rev D November 2016 Chapter 2 38 ...
Page 60: ...DMTA 10004 01EN Rev D November 2016 Chapter 3 48 ...
Page 102: ...DMTA 10004 01EN Rev D November 2016 Chapter 6 90 ...
Page 222: ...DMTA 10004 01EN Rev D November 2016 Chapter 11 210 ...
Page 254: ...DMTA 10004 01EN Rev D November 2016 Chapter 13 242 ...
Page 274: ...DMTA 10004 01EN Rev D November 2016 Chapter 14 262 ...
Page 286: ...DMTA 10004 01EN Rev D November 2016 Chapter 15 274 ...
Page 294: ...DMTA 10004 01EN Rev D November 2016 Appendix A 282 ...
Page 300: ...DMTA 10004 01EN Rev D November 2016 Appendix C 288 ...
Page 306: ...DMTA 10004 01EN Rev D November 2016 List of Figures 294 ...
