Reed Instruments R7900 User manual

Ultrasonic
Thickness
Gauge
Instruction
Manual
R7900
www. .com [e-mail]1.800.561.8187

2
Table of Contents
Introduction ................................................................................................ 4
Product Quality........................................................................................... 4
Safety ......................................................................................................... 4
Features...................................................................................................... 4
Specications............................................................................................. 5
Included...................................................................................................... 5
Instrument Description............................................................................... 6
Keypad Description.................................................................................... 6
Display Description .................................................................................... 7
Operating Instructions...........................................................................8-13
Setting Ultrasonic Sensor Frequency.................................................... 8
Zero Calibration..................................................................................... 8
Adjusting the Sound Velocity .............................................................8-9
Preparing the Measurement Surface................................................... 10
Taking Thickness Measurements......................................................... 10
Auto Power OFF.................................................................................. 10
Sound Velocity Measurements of a Material with
a Known Thickness.............................................................................. 11
Sound Velocity Calibration .............................................................11-12
Two Point Calibration .......................................................................... 12
Setting Alarm Thickness Limits ........................................................... 13
Minimum Capture Measurements ....................................................... 13
Measurement Methods .......................................................................13-14
Menu Options......................................................................................14-15
System Setup .................................................................................14-15
Memory Manager ................................................................................ 15
System Reset ...................................................................................... 15
Internal Memory Operation ...................................................................... 16
Reviewing Stored Data........................................................................ 16
continued...
www. .com [e-mail]1.800.561.8187

3
Maintenance............................................................................................. 16
Cleaning the Test Piece ....................................................................... 16
Protecting the Ultrasonic Sensor......................................................... 16
Replacing the Ultrasonic Sensor ......................................................... 16
Battery Replacement................................................................................ 17
Applications.............................................................................................. 17
Accessories and Replacement Parts ....................................................... 17
Appendix .............................................................................................18-22
Measurements on Cylindrical Surfaces ............................................... 18
Measuring Compound Profiles............................................................ 18
Measuring an Un-Parallel Surface ....................................................... 18
Influence of Material's Temperature .................................................... 19
Material with Large Attenuation........................................................... 19
Measuring Castings............................................................................. 19
Preventing Errors................................................................................. 20
Reference Test Pieces ..................................................................... 20
Ultra-Thin Material..........................................................................21-22
Rust, Corrosion, and Pits................................................................. 21
Error in Identifying Material.............................................................. 21
Degradation of Probe....................................................................... 21
Overlapped Material and Compound Material................................. 21
Influence of Metal Surface Oxidation..........................................21-22
Abnormal Readout of Thickness...................................................... 22
Utilization and Selection of a Coupling Gel (R7950) ........................ 22
Product Care ............................................................................................ 22
Product Warranty ..................................................................................... 23
Product Disposal and Recycling .............................................................. 23
Product Support....................................................................................... 23
www. .com [e-mail]1.800.561.8187

4
Introduction
Thank you for purchasing your REED R7900 Ultrasonic Thickness Gauge.
Please read the following instructions carefully before using your instrument.
By following the steps outlined in this manual your meter will provide years
of reliable service.
Product Quality
This product has been manufactured in an ISO9001 facility and has been
calibrated during the manufacturing process to meet the stated product
specications. If a certicate of calibration is required please contact the
nearest authorized REED distributor or authorized Service Center. Please
note an additional fee for this service will apply.
Security
Never attempt to repair or modify your instrument. Dismantling your
product, other than for the purpose of replacing batteries, may cause
damage that will not be covered under the manufacturer's warranty.
Servicing should only be provided by an authorized service center.
Features
• Measuresawiderangeofmaterialincluding;metals,plastic,ceramics,
composites, epoxies, glass, and other ultrasonic conductive materials
• Easy-to-readbacklitLCDdisplay
• Userselectableunitofmeasure(in/mm)
• Internalmemorystoresupto500measurements
• Displayssoundvelocityatthetouchofabutton
• Zeroadjustmentbutton
• UseradjustableHigh/Lowalarms
• Built-intwo-pointcalibrationfunction
• Autosleep,shutoffandlowbatteryindicator
www. .com [e-mail]1.800.561.8187

5
Specifications
MeasuringRange: 0.03to15.7"(0.65to400mm)
Accuracy: ±0.04mm(<10mm)
 ±(0.1%rdg.+0.04mm)(<100mm)
 ±(0.3%rdg.)(>100mm)
Resolution: 0.01mmor0.1mm(<100mm)
 0.1mm(>100mm)
VelocityRange: 1000to9999m/s(0.039to0.394in/µs)
Compatible Materials: Ultrasonic conductive materials
 (ie.metals,plastics,ceramics,
 composites,epoxies,glass)
SamplingTime: Lessthan1second
Display: 4-Digit,LCD
Backlit Display: Yes
ProbeLength: 3'(36")
InternalMemory: Yes(upto500readings,
 5lesupto100each)
LowBatteryIndicator: Yes
Power Supply: 2 AA Batteries
BatteryLife: Approx.100hours(Alkaline)
Product Certications: CE
OperatingTemperature: 32to122°F(0to50°C)
StorageTemperature: -4to140°F(-20to60°C)
OperatingHumidityRange: 20to80%
Dimensions: 5.9x2.9x1.3"(150x74x32mm)
Weight: 8.4oz(238g)
Included
• UltrasonicCouplantGel
• Probe
• HardCarryingCase
• Batteries
www. .com [e-mail]1.800.561.8187

6
Instrument Description
1. LCDDisplay
2. Calibration Test Block
3. Probe Inputs
Keyboard Description
1. ZeroButton
2. Mode Button
3. Down Button
4. Enter Button
5. Up Button
6. BacklightON/OFFButton
7. Power Button
8. Save/BrowseButton
9. Velocity Button
R7900
Ultrasonic Thickness Gauge
Ultrasonic Thickness Gauge
3
2
34
5
6
7
8
9
Ultrasonic Thickness Gauge
www. .com [e-mail]1.800.561.8187

7
Display Description
3
6
m/s
HIGH
MENU ALARM
F1 5M
1. Measured Value
2. Menu Settings
3. Saved File Name
4. Ultrasonic Sensor Frequency
5. Alarm Thickness Settings
6. Battery Indicator
7. Minimum Capture Mode
8. Coupling Indicator
9. Gain Indicator
www. .com [e-mail]1.800.561.8187

8
Operating Instructions
1. Insert the ultrasonic sensor into the probe sockets on the meter.
2. Press, hold an release the button for 2 seconds to turn the meter
on. Press the button to turn the meter off.
3. TheLCDwillbrieydisplayinformationaboutthemeter,andthen
show the current set sound velocity.
Setting Ultrasonic Sensor Frequency
1. Press the button to highlight the ultrasonic sensor frequency
setting on the display.
2. Continuously press the buttontotogglebetween2MHz,5MHz,
7MHz,10MHzandZWfrequencies.
3. To exit, press the button or by carrying out a measurement.
Zero Calibration
1. After setting the correct ultrasonic sensor frequency, set the sound
velocityto5900m/s(seeAdjusting the Sound Velocityfordetails).
2. Selecttheproperreceivinggain(seeSystem Setupfordetails).
3. Coatthe4mmcalibrationtestblockwithcouplinggel(R7950)and
place the sensor on the calibration test block while ensuring the
coupling indicator " "appearsontheLCDdisplay.
4. OncethecouplingindicatorappearsontheLCDdisplaypressthe
button to initiate zero calibration.
5. The meter will beep and then the screen will indicate that the calibration
is complete.
6. If zero calibration is not properly completed the meter will retain the
original value.
7. To delete the calibration data, see Memory Manager section for details.
Adjusting the Sound Velocity
1. While the meter is on, press the button and the meter will
display the current sound velocity.
2. Press the button to switch between the 5 pre-loaded sound
velocities, or press the and buttons to match the sound
velocity of the material under test as shown in the following table.
continued...
www. .com [e-mail]1.800.561.8187

9
Material Sound Velocity
(m/s) (inch/µs)
Aluminum 6320 to 6400 0.250
Zinc 4170 0.164
Silver 3607 0.142
Gold 3251 0.128
Tin 2960 0.117
Steel, Common 5920 0.233
Steel, Stainless 5740 0.226
Brass 4399 0.173
Copper 4720 0.186
Iron 5930 0.233
Case Iron 4400 to 5820 0.173 to 0.229
Lead 2400 0.094
Nylon 2680 0.105
Titanium 5990 0.236
SUS 5970 0.240
Epoxy Resin 2540 0.100
Ice 3988 0.222
Plexiglass 2692 0.106
Grey Cast 4600 0.180
Porcelain 5842 0.230
Glass(Quartz) 5570 0.220
Polystyrene 2337 0.092
PVC 2388 0.094
Quartz Glass 5639 0.222
Rubber, Vulcanized 2311 0.091
Teon 1422 0.058
Water 1473 0.058
continued...
www. .com [e-mail]1.800.561.8187

10
Preparing the Measurement Surface
1. Cleananydust,dirtorrustofftheobject,andremoveanycoating
such as paint.
2. Smooththesurfaceoftheobjectbygrindingorpolishingit.Youcan
also use a coupling gel with a high viscosity.
Important Note: In any ultrasonic measurement scenario, the shape and
roughness of the desired test material are of great importance. Rough,
uneven surfaces will prevent the ultrasonic sensor from seating properly
against the surface, thus limiting the penetration of ultrasound through the
material, resulting in unstable and therefore, unreliable measurements.
Taking Thickness Measurements
1. Setthesoundvelocityonthemeter(seeAdjusting the Sound
Velocityfordetails).
2. Apply coupling gel on the material, place the sensor rmly against
the desired measurement area.
Note: For most applications a single droplet of coupling gel is sufcient.
3. Verify that the coupling Indicator " "appearsontheLCDdisplay.
4. ReadthemeasurementontheLCDdisplay.
5. When you remove the ultrasonic sensor the value will stay on the
LCDandthecouplingindicator" " will disappear.
6. Press the button to save the measurement if applicable.
7. If the coupling indicator " " does not appear on the display,
or the measured values appear to be erratic, verify that there is an
adequate amount of coupling gel in between the ultrasonic sensor
and the material under test. It is also important that the ultrasonic
sensorsitsatagainstthematerial.
Auto Power OFF
To preserve battery life, the meter is programmed to turn itself after
approximately 3 minutes of inactivity. To disable this option, please see
System Setup section for details.
continued...
www. .com [e-mail]1.800.561.8187

11
Sound Velocity Measurements of a Material with a
Known Thickness
The sound velocity of a material can be measured using a test piece with
a known thickness. Select a test piece with a minimum wall thickness of
20.0mm.Turnofftheminimumcapturingfunction(seeSystem Setup
sectionfordetails)priortotakingmeasurement.
1. Measure the test piece with a caliper or micrometer to conrm
the thickness.
2. Apply coupling gel on the material, place the sensor rmly against
the desired measurement area.
Note: For most applications a single droplet of coupling gel is sufcient.
3. Remove the ultrasonic sensor from the measurement area and
adjustthemeasuringdisplayuntiltheactualthicknessismetby
pressing the and buttons and press the button to conrm
your selection.
4. TheLCDwilldisplaythesoundvelocity.
5. Press the button to save the value if applicable.
Sound Velocity Calibration
1. Start by performing a zero calibration to the ultrasonic sensor.
2. Measure the actual thickness of the test piece with a caliper
or micrometer.
3. Selectasoundvelocityfromthepre-loadedlist(chooseanyone).
4. Apply coupling gel on the material, place the sensor rmly against
the desired measurement area.
Note: For most applications a single droplet of coupling gel is sufcient.
5. TheLCDwilldisplayameasurementreadingofthetestpiece.
Note: The reading will be off as the sound velocity is not correct.
6. Remove the ultrasonic sensor from the test piece, go into the
velocity interface by pressing the button and increasing the
current sound velocity a little at a time by pressing the button.
continued...
www. .com [e-mail]1.800.561.8187

12
7. Take another measurement of the test piece to verify if the thickness
reading is getting closer to the known thickness or not. If for some
reason it is now farther away than before, reduce the velocity a little
by pressing the button. Check the thickness again to make sure
thatyouaregettingcloser.Continueadjustingthesoundvelocityuntil
the thickness reading is correct.
8. Once you have reached the known thickness of the test piece, press
the button to conrm your sound velocity setting. From this point,
the sound velocity is calibrated and you can now take measurements of
the same material with condence.
Two Point Calibration
1. Select two standard samples of the same material to be measured,
among which one has a thickness equal to or slightly higher than the
tested piece, and the thickness of another test piece is slightly lower
than the tested piece.
2. Before carrying out 2-point calibration, turn off the "Minimum
Capture"functionanderasetheCALdatainthe"MemoryManager".
3. Set the 2-point calibration to ON in the "System Setup" menu.
4. Press twice on the button to return to the main display.
5. Press the button at any time during measurement to enter the
2-PointCAL.
6. Measure the thinner standard test piece.
7. Remove the ultrasonic sensor from the test piece and use the
and buttonstoadjustthemeasurementtostandardvalue.
8. Press the buttonandtheLCDwillprompttomeasurethe
thicker piece.
9. Measure the thicker standard test piece.
10. Remove the ultrasonic sensor from the test piece and use the
and buttonstoadjustthemeasurementtostandardvalue.
11. Press the button when the two-point calibration is completed.
continued...
www. .com [e-mail]1.800.561.8187

13
Setting Alarm Thickness Limits
The R7900 will alarm when the measured value is beyond the pre-set
limits. When the measurement is lower than the low pre-set limit or higher
than the high pre-set limit, the alarm will sound. To enter the alarm setting,
follow steps 1 through 6 below.
1. Press the buttontohighlightthe"Alarm"settingontheLCD.
2. Press the buttontoadjusttheLOWlimit.
3. Press the and buttonstoadjusttheuserdenedLOW
alarm value.
4. Press the buttontosavetheLOWlimit,andtosettheHIGHlimit.
5. Press the and buttonstoadjusttheuserdenedHIGHalarm
value, and press the buttontosavetheHIGHlimit.
6. To exit the limit setting, press the button or by carrying out
a measurement.
Minimum Capture Measurements
When the ultrasonic sensor couples with the test piece it will display the
current measurement. When it is lifted away it will display the minimum
valueofthemeasurementcarriedoutwhiletheMINIndicatorashesfor
severalseconds.MeasurementstakenduringtheMINindictorashing
cycle will continue to be part of the minimum value capturing. If you carry
outmeasurementsaftertheMINIndicatorstopsashingtheminimum
value capturing will re-start. The MIN indicator will only display when the
minimumcapturefunctionisON(seeSystem Setupsectionfordetails).
Measurement Methods
There are three base measurement methods:
1. Single measurement method: This method involves measuring the
thickness at a single point.
2. Double measurement method: This method
involves performing two thickness measurements
near a single spot rotating the ultrasonic sensor
from 0 to 90° respectively, with respect to the split
face(seeFigureA).Takethesmallerofthetwo
indicated values as the thickness of the material.
continued...
90º
Figure A
www. .com [e-mail]1.800.561.8187

14
3. Multi-point measurement: This method involves performing a
number of measurements within a circle having a maximum diameter
ofabout1.18"(30mm)(seeimagebelow).Taketheminimum
indicated value as the thickness of the material.
Menu Options
The menu function controls the settings and functions of the meter. To
enter the menu, press the button to highlight the menu option on the
LCDandpressthe button.
System Setup
1. While in the menu, highlight the "System Setup" option and press the
button to enter this menu.
2. Press the and buttons to scroll through the "System Setup" menu.
3. When the required setting as shown below, is highlighted, press the
button to select it and toggle between units.
Note: To set brightness, press button to enter the setting, and use
the and buttonstoadjustthebrightness.
4. Once completed, press the button to save and exit.
System Setup Menu Settings are as follows:
1. Measurement Units: Metric and Imperial
2. Receiving Gain:LOW(resolutionof0.1mm)andHIGH(resolution
of0.01mm).LOWismainlyusedformeasuringcoarsematerialwith
high scatter and small sound absorption, such as cast aluminum,
cast copper, and other metallic parts.
3. Minimum Capture Measurement: OFF and ON
4. 2-Point Calibration: OFF and ON
5. Auto Down:Power-savingmodeON(default)
continued...
www. .com [e-mail]1.800.561.8187

15
6. Baud Rate: 1200, 2400, 4800, 9600
7. Set Brightness: UP to darken, DOWN to lighten
Memory Manager
1. While in the menu, highlight the "Memory Manager" option and press
the button to enter this menu.
2. Press the and buttons to scroll through the "Memory
Manager" menu.
3. Press the button to select the required option as shown below:
• Erase File: Clears selected les
• Erase All Data: Clears all saved les
• Erase CAL data: Clears calibrating data
4. Press the buttonagaintoconrm(YES)or"Menu"toescape.
System Reset
While in the menu, highlight the "About Software" option and press the
button to enter this menu. Press the button to restore the meter to
its factory default settings for. Upon completion, the meter will shut down.
www. .com [e-mail]1.800.561.8187

16
Internal Memory Operation
The internal memory is divided into 5 les, F1 to F5. Each le can save up
to 100 measurement values.
Note: Before saving your data, be sure to set the le number rst.
1. Press the button tohighlightthe"SaveFileName"ontheLCD.
2. Press the button to scroll through the memory les, F1 to F5.
3. Press the button to save and exit.
Reviewing Stored Data
1. Press the button tohighlightthe"SaveFileName"ontheLCD.
2. Press the button to scroll through the memory les, F1 to F5.
3. Press the button to select the appropriate le number and to view
the saved values.
4. Press the and buttons to scroll through the saved values.
5. If required, press the button to erase the current saved value.
Maintenance
Cleaning the Test Piece
After taking a measurement, clean the test pieces to prevent them from
rusting. If the pieces are not to be used for a long period of time, coat
them with oil to prevent rust.
Protecting the Ultrasonic Sensor
Be sure to clean the ultrasonic sensor and cable after each use. Grease, oil
and dust will cause the cable to dry out and shorten life expectancy. The
temperatureofthesurfacebeingmeasuredshouldnotexceed140°F(60°C).
Replacing the Ultrasonic Sensor
Thedegradationandwearoftheprobe'sinterlayerplatewillinuence
measurements. Replace the probe when the following occurs:
• If it always displays the same value when measuring different
thicknessesor;
• When a measurement displays no value.
www. .com [e-mail]1.800.561.8187

17
Battery Replacement
1. When the low battery symbol appears on the display, replace
the batteries.
2. Remove the battery cover on the back and insert two new AA batteries.
Note: If the unit will not be used for a long period of time, remove the
batteries to avoid battery leakage and corrosion of the battery contacts.
Applications
• Monitoringandverifyingpipesandpressurevessels
• Industrialmanufacturing
Accessories and Replacement Parts
• CA-52A Soft Carrying Case
• R8888HardCarryingCase
• R7900-PROBE Replacement Probe
• R7950 Ultrasonic Couplant Gel
• R7950/5LUltrasonicCouplantGel,5L
• R7950/12 Ultrasonic Couplant Gel, pack of 12
Don't see your part listed here? For a complete list of all accessories and
replacement parts visit your product page on www.reedinstruments.com.
www. .com [e-mail]1.800.561.8187

18
Appendix
Measurements on Cylindrical Surfaces
When measuring cylindrical material, such as pipes or oil tubes, it is
importanttoproperlyadjusttheanglebetweentheultrasonicsensor's
crosstalk interlayer plate and the axial line of the material being measured.
1. Couple the sensor with the material being measures.
2. Make the sensor's crosstalk interlayer plate perpendicular or parallel
to the axial line of the material under test.
3. Shake the sensor vertically along the axial line of the material under
test, the readouts displayed on screen will change regularly.
4. Use the minimum readout.
The standard for selecting the angle between the sensor's crosstalk
interlayer plate and the axial line of the material under test depends on the
curvature of the material under test. For a pipe with a large diameter the
sensor's crosstalk interlayer plate should be perpendicular to the axial line of
the material under test. For a pipe with small diameter, the sensor's crosstalk
interlayer plate can be both parallel and perpendicular to the axial line of the
material under test, and take the minimum readout as the thickness.
Measuring Compound Profiles
Whenthematerialbeingmeasuredhasacompoundprole(suchas
abendinapipe),onecanusetheprocedurestomeasurecylindrical
surfaces. The exception is that one should have two analyses and get
two results when the sensor's crosstalk interlayer plate is both parallel
and perpendicular to the axial line of the material under test. Take the
minimum readout as the material thickness.
Measuring an Un-Parallel Surface
To get a satisfactory ultrasonic response, the other surface of the
material under test must be parallel to or co-axial with the surface being
measured, otherwise it will cause a measuring error or even provide no
displayed reading.
continued...
www. .com [e-mail]1.800.561.8187

19
Influence of Material's Temperature
Both the thickness and transmitting speed of ultrasonic waves are
inuencedbytemperature.Ifthereisahighrequirementofmeasuring
accuracy, please use one of the comparison methods listed below:
1. Use a test piece of the same material being measured, under the
same temperature.
2. Obtain the temperature compensation coefcient.
3. Use this coefcient to correct the actual measurement of the material
being tested.
Material with Large Attenuation
Materialwithporousandcoarseparticles(suchasbre)willcausealarge
scatter and energy attenuation in the ultrasonic wave. This will cause
abnormalreadingsorprovidenoreadingsonthedisplay(generally,the
abnormalreadingsarelessthantheactualthickness).Thesetypeof
materials cannot be measured by our ultrasonic thickness gauges.
Measuring Castings
Castings will cause large attenuations in sound energy due to coarse
crystal particles and a not-so-dense structure. The attenuation is due to
the material's scatter and absorption of sound energy. Coarse out-phase
structuresandcoarsecrystalparticleswillcauseabnormalreection(i.e.
agrass-shapedortree-shapedecho)resultinginerrorsinthereadings.
Whenthecrystalparticleiscoarse,theanisotropyinexibilityinmetal's
crystallizing direction will be obvious. This results in difference in sound
velocities in different directions, with the maximum difference being up to
5.5%.Thecompactnessindifferentpositionsoftheworkpieceisdifferent,
which will also cause difference in sound velocity. All of these will produce
inaccuracies in the measurements.
While measuring castings pay attention to the following:
1. When measuring casting with an un-machined surface use engine
oil, consistent grease, or water glass as a coupling gel.
2. Calibrate the sound velocity for the material under test with a
standard test piece having the same material and measuring
direction as that of the material being measured.
3. If necessary, take a 2-point calibration.
continued...
www. .com [e-mail]1.800.561.8187

20
Preventing Errors
Reference Test Pieces
To maintain high accuracy when taking measurements of different
materials, it is important to use a standard test piece that resembles the
material and conditions being measured. The ideal reference test pieces
should be a group of test pieces with different thicknesses made of the
same materials that is going to be measured. The test pieces can provide
calibratingfactorsforthemeter(suchasthemicrostructureofthematerial,
heat-treatingcondition,directionofparticles,surfaceroughness,etc.).
To meet the highest requirements of accuracy a set of reference test
pieces are critical.
Under most situations satisfactory measuring accuracies can be met
with only one reference test piece. This should be the same material and
similarthicknesstothematerialundertest.Takeaneven-surfacedobject,
measure it by using a micrometer, then use it as a test piece.
For thin material, when its thickness is near to the low limit of the sensor's
measuring range, you can use a test piece to determine the accurate low
limit. Never measure a material with a thickness lower than the low limit.
When the material under test is thick, especially an alloy with complex
internalstructure,selectatestpiecesimilartotheobjectfromagroupof
test pieces, giving you an idea of calibration.
For most casting and forging, their internal structures have some direction.
In different directions, the sound velocity will experience some change. To
solve this problem, the test piece should have an internal structure with
same direction as that of the material under test, and the transmitting
direction of sound wave in it should also be same as that of the material.
Under certain circumstances, referring to a material speed-of-sound
table can replace reference test pieces. The value in the speed-of-sound
table may have some difference from the actual measured values due to
difference in the material's physical and chemical characteristics. This is
usually used for measuring low-carbon steel, and can only be taken as a
rough measurement.
continued...
www. .com [e-mail]1.800.561.8187