ASTM D8153-22

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8153 − 22
Standard Test Method for
Determination of Soil Water Contents Using a Dielectric
Permittivity Probe
This standard is issued under the fixed designation D8153; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope multiplying the water content (in volume of water per volume
of soil) by the density of water.
1.1 Thistestmethoddescribestheproceduresformeasuring
the water mass per unit volume of soil and soil-aggregate by 1.3 Water content most prevalent in engineering and con-
use of an in situ permittivity probe. Measurements are taken at struction activities is known as the gravimetric water content,
adepthbeneaththesurfaceofthesoildeterminedbythedesign ω,andistheratioofthemassofthewaterinporespacestothe
of the probe. total mass of solids, expressed as a percentage. To determine
1.1.1 For limitations see Section 6 on Interferences. this quantity, the bulk density of the soil under measurement
must also be determined.
1.2 The permittivity probe is inserted into a hole drilled or
punched into the soil being measured. As its name indicates, 1.4 Units—The values stated in SI units are to be regarded
the probe measures the dielectric permittivity of the soil into as the standard. Reporting the test results in units other than SI
which it is placed. Two electrodes, connected to an oscillating shall not be regarded as nonconformance with this standard.
circuit, are mounted a predetermined distance apart. These
1.5 All observed and calculated values shall conform to the
electrodesactastheplatesofacapacitor,withthesoilbetween
guidelines for significant digits and rounding established in
the plates forming the capacitor dielectric.
Practice D6026.
1.2.1 Theprobecircuitcreatesanoscillatingelectricfieldin
1.5.1 For purposes of comparing, a measured or calculated
the soil. Changes in the dielectric permittivity of the soil are
value(s) with specified limits, the measured or calculated
indicatedbychangesinthecircuit’soperatingfrequency.Since
value(s) shall be rounded to the nearest decimal or significant
water has a much higher dielectric constant (80) than the
digits in the specified limits.
surrounding soil (typically around 4), the water content can be
1.5.2 Theproceduresusedtospecifyhowdataarecollected/
related by a mathematical function to the change in dielectric
recorded and calculated in this standard are regarded as the
permittivity, and, consequently, the changes in the circuit’s
industry standard. In addition, they are representative of the
operating frequency.
significant digits that should generally be retained. The proce-
1.2.2 Theconstruction,deployment,andoperatingprinciple
dures used do not consider material variation, purpose for
of the device described in this test method differ from other
obtaining the data, special purpose studies, or any consider-
methods that measure the dielectric constant, bulk electrical
ations for the user’s objectives; and it is common practice to
conductivity, complex impedance, or electromagnetic imped-
increase or reduce significant digits of reported data to com-
ance (see Test Methods D6780/D6780M, D7698, and D7830/
mensurate with these considerations. It is beyond the scope of
D7830M) of the soil and relate the results to water mass per
this standard to consider significant digits used in analysis
unit volume and/or water content.
methods for engineering design.
1.2.3 The water content of the soil measured by the permit-
1.6 This standard does not purport to address all of the
tivity probe is the volumetric water content, expressed as the
safety concerns, if any, associated with its use. It is the
ratioofthevolumeofwatertothetotalvolumeoccupiedbythe
responsibility of the user of this standard to establish appro-
soil. This quantity is often converted, and displayed, by the
priate safety, health, and environmental practices and deter-
probe in units of mass of water per volume of soil, or water
mine the applicability of regulatory limitations prior to use.
mass per unit volume. This conversion is performed by
1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
ization established in the Decision on Principles for the
Rock and is the direct responsibility of Subcommittee D18.08 on Special and
Development of International Standards, Guides and Recom-
Construction Control Tests.
mendations issued by the World Trade Organization Technical
Current edition approved June 1, 2022. Published July 2022. DOI: 10.1520/
D8153-22. Barriers to Trade (TBT) Committee.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8153 − 22
2. Referenced Documents 3.2.2 capacitance standard, n—a reference material or ob-
2 jectpreparedofsoil,soilandrock,orengineeredmaterialsthat
2.1 ASTM Standards:
has a stated dielectric permittivity value and an associated
C231/C231MTestMethodforAirContentofFreshlyMixed
measurement uncertainty.
Concrete by the Pressure Method
D653Terminology Relating to Soil, Rock, and Contained
NOTE1—Theterm“bulkdensity”isusedthroughoutthisstandard.This
termhasdifferentdefinitionsinASTMD653,dependingonthecontextof
Fluids
its use. For this standard, however, “bulk density” refers to, as defined in
D1556/D1556MTest Method for Density and Unit Weight
ASTMD653,“thetotalmassofpartiallysaturatedorsaturatedsoilorrock
of Soil in Place by Sand-Cone Method
per unit total volume.”
D2167Test Method for Density and Unit Weight of Soil in
Place by the Rubber Balloon Method
4. Summary of Test Method
D2216Test Methods for Laboratory Determination ofWater
4.1 Thesurfaceofaninsitutestsitewherethewatercontent
(Moisture) Content of Soil and Rock by Mass
is to be determined is scraped to a smooth, coplanar surface.
D2487Practice for Classification of Soils for Engineering
4.2 An access hole, with a nominal diameter of 19 mm, is
Purposes (Unified Soil Classification System)
punched,drilled,orauguredintothesoil.Theholeshallextend
D2488Practice for Description and Identification of Soils
(Visual-Manual Procedures) a minimum of 25 mm below the end of the probe.
D2937Test Method for Density of Soil in Place by the
4.3 The probe is inserted into the access hole in such a
Drive-Cylinder Method
manner as to minimize any disturbance to the integrity of the
D3740Practice for Minimum Requirements for Agencies
hole.
Engaged in Testing and/or Inspection of Soil and Rock as
4.4 Ameasurement of the soil with the permittivity probe is
Used in Engineering Design and Construction
acquired. The measurement consists of a series of readings of
D4718/D4718MPractice for Correction of Unit Weight and
the oscillator frequency of the circuit associated with the
Water Content for Soils Containing Oversize Particles
dielectric permittivity. The readings are averaged to obtain a
D6026Practice for Using Significant Digits and Data Re-
final result.
cords in Geotechnical Data
D6780/D6780MTest Methods for Water Content and Den- 4.5 The resulting circuit reading, along with the calibration
equation that relates this reading with the water mass per unit
sity of Soil In situ by Time Domain Reflectometry (TDR)
D6938TestMethodsforIn-PlaceDensityandWaterContent volumeofthesoil,areusedtocomputethewatermassperunit
volume of the soil.
of Soil and Soil-Aggregate by Nuclear Methods (Shallow
Depth)
4.6 If the data are available, then this calculated water mass
D7698Test Method for In-Place Estimation of Density and
per unit volume, in conjunction with the independently deter-
Water Content of Soil andAggregate by Correlation with
mined bulk density of the soil, may be used to determine the
Complex Impedance Method
(gravimetric) water content of the soil. Bulk density may be
D7830/D7830MTest Method for In-Place Density (Unit
determinedbytestmethodssuchastheonesdescribedin,Test
Weight) and Water Content of Soil Using an Electromag-
MethodsD1556/D1556M,D2167,D2937,D6938,andD8167/
netic Soil Density Gauge
D8167M, as examples.
D8167/D8167MTest Method for In-Place Bulk Density of
Soil and Soil-Aggregate by a Low-Activity Nuclear
5. Significance and Use
Method (Shallow Depth)
5.1 The soil permittivity probe is used for the following
E177Practice for Use of the Terms Precision and Bias in
purposes:
ASTM Test Methods
5.1.1 The test method described is useful as a rapid,
E691Practice for Conducting an Interlaboratory Study to
nondestructive technique for bulk measurements of the water
Determine the Precision of a Test Method
mass per unit volume of soil and soil-aggregate which may, in
conjunction with an independent bulk density determination,
3. Terminology
be used in the determination of dry density.
3.1 Definitions:
5.1.2 The test method is used for quality control and
3.1.1 Fordefinitionsofcommontechnicaltermsusedinthis
acceptance testing of compacted soil and soil-aggregate mix-
standard, refer to Terminology D653.
tures as used in construction and also for research and
3.2 Definitions of Terms Specific to This Standard:
development.Thenondestructivenatureallowsrepetitivemea-
3.2.1 permittivity probe, n—an in situ electronic probe that
surementsatasingletestlocationandstatisticalanalysisofthe
utilizes the measurement of the dielectric permittivity of the
results.
surrounding soil to determine the water mass per unit volume
5.1.3 Volumetric Water Content—The fundamental assump-
of the soil.
tionsinherentinthetestmethodarethatthedielectricconstants
value measured by the system in a given test site composed of
soil or soil-aggregate are directly correlated to the volumetric
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
watercontentofthesoilorsoil-aggregate,andthatthematerial
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
is homogeneous. (See 6, “Interferences.”)
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. NOTE 2—The quality of the result produced by this standard is
D8153 − 22
dependent on the competence of the personnel performing it, and the
cause higher or lower water mass per unit volume measure-
suitability of the equipment and facilities used. Agencies that meet the
ments. Where lack of uniformity in the soil due to layering,
criteria of Practice D3740 are generally considered capable of competent
aggregate or voids is suspected, the test site shall be excavated
and objective testing/sampling/inspection/etc. Users of this standard are
and visually examined to determine if the test material is
cautioned that compliance with Practice D3740 does not in itself assure
representative of the in situ material in general and if an
reliable results. Reliable results depend on many factors; Practice D3740
provides a means of evaluating some of those factors.
oversize correction is required in accordance with Practice
D4718/D4718M.
6. Interferences
6.1 The elemental and/or molecular composition of the
7. Apparatus
material being tested can affect the measurement, and adjust-
7.1 Soil Permittivity Probe—While exact details of con-
ments may be necessary (seeAnnexA1.8). Different soils with
struction of the apparatus may vary, the system is approxi-
solids composed of different elements or molecular structure
mately 140 mm long and 20 mm in diameter (see Fig. 1), and
may cause correspondingly different dielectric constant re-
shall consist of:
sponses with this instrument, thereby possibly yielding differ-
7.1.1 Bottom Conductor—Atapered, conducting cylindrical
entwatermassperunitvolumemeasurementswithsoilsofthe
assembly that attaches below the dielectric spacer.
same water mass per unit volume.
7.1.2 Dielectric Spacer—A non-conducting material, like-
6.2 The water mass per unit volume calculated by this test
wise cylindrical and tapered, that attaches between the bottom
method is not necessarily the average water content within the
conductor and the top conductor
volume of the sample involved in the measurement. The
7.1.3 Top Conductor—A tapered, conducting cylindrical
measured value is biased by the water mass per unit volume of
assembly that attaches above the dielectric spacer and directly
the material closest to the dielectric spacer in the probe
below the surface plate.
assembly (see 7.1.2). The volume of soil and soil-aggregate
represented in the measurement is indeterminate and will vary 7.2 Surface Plate—A disc that, when the soil permittivity
probe is engaged with the soil for a measurement, lies directly
with the water content and elemental and/or molecular com-
on the surface of the soil.
position of the material. In general, the greater the water mass
per unit volume of the material, the smaller the volume
7.3 Positioning Handles—Two collinear handles that attach
involved in the measurement. Approximately 50 % of the
above,andparallelto,thesurfaceplate.Thesehandlesareused
typicalmeasurementresultsfromthewatercontentofthe50to
to push the soil permittivity probe into the access hole where
75 mm diameter centered about the dielectric spacer.
the in situ measurement is being taken, and then again to pull
6.3 Oversize particles or large voids in close proximity to the soil permittivity probe back out of the hole once the
the dielectric spacer in the probe assembly (see 7.1.2) may measurement is complete.
FIG. 1 Soil Permittivity Probe, Drawn to Scale
D8153 − 22
7.4 Control Unit—Acomputer,nucleardensitygauge,wire- to the probe and better ensure maximum contact between the
less communications device, or similar electronic devices that probe and the hole surface.
contains the operating software for the permittivity probe;
9.6 Take a measurement with the soil permittivity probe,
typical operation is performed wirelessly, but can be operated
using the device to which it is connected electronically to
through an RS232 cable connection.
collect and interpret the results. The measurement reading
7.5 Site Preparation Device—Aplate, straightedge, or other
typically become stable within five seconds after installation,
suitable leveling tool that may be used for planing the test site with continuous updating (at an approximate rate of one
to the required smoothness.
measurement per second) by the device.
7.6 Drive Pin—A pin with a nominal diameter of 19 mm
9.7 Once the desired measurements are collected at this test
used to prepare a hole in the test site for inserting the probe.
site, carefully raise the soil permittivity probe out of the access
hole. Again, be careful to avoid excessive twisting motion
7.7 Drive Pin Guide—A fixture that keeps the drive pin
whilepullingupwiththehandlestoavoidanysheardamageto
perpendicular to the test site. Generally part of the site
the probe, and to better ensure maximum contact between the
preparation device.
probe and the interior surface of the hole in the event that the
7.8 Hammer—Heavyenoughtodrivethepintotherequired
access hole must be used again for successive readings with
depth without undue distortion of the hole.
other instruments.
7.9 Drive Pin Extractor—Atoolthatmaybeusedtoremove
the drive pin in a vertical direction so that the pin will not 10. Calculation or Interpretation of Results
distort the hole in the extraction process.
10.1 As mentioned previously, the soil permittivity probe
7.10 Slide Hammer, with a Drive Pin Attached—As an responseisdependentuponthevolumetricwatercontentofthe
alternativeto7.5–7.8,mayalsobeusedbothtoprepareahole
soil. The device to which the soil permittivity probe is
in the material to be tested and to extract the pin without connected electronically will compute the water mass per unit
distortion to the hole.
volume, denoted by M .
w
10.2 The aforementioned value of M is calculated by the
w
8. Calibration
calibrationequationforthespecificsoilorsoil-aggregateunder
8.1 Probe calibration shall be performed in accordance with test, where M is the independent variable of the equation, and
w
the processes described in Annex A1.
the oscillator frequency output of the probe circuit is the
dependent variable.
9. Procedure
10.3 Once M is calculated by the device, it is displayed by
w
9.1 Remove all loose and disturbed material and additional
the device. The water mass per unit volume value is the mass
material as necessary to expose the true surface of the material
of water contained in a given volume of soil or soil-aggregate.
to be tested.
The water mass per unit volume value, denoted by M ,is
w
calculated as
9.2 Prepare an area sufficient in size to accommodate the
probe by grading or scraping the area to a smooth condition to Mw 5θρ (1)
w
obtain maximum contact between the surface plate and mate-
where ρ is the density of water at 4.0 ºC (999.8395 kg/m )
w
rial being tested. The optimum condition is total contact
and θ is the volumetric water content of the soil.
betweenthebottomsurfaceofthesurfaceplateandthesurface
of the material being tested.
10.4 Calculated M valuesaredisplayedtoasensitivity(the
w
nearest value) of 1 kg/m .
9.3 Makeaholeperpendiculartothepreparedsurfaceusing
either a hammer and a drive pin or a slide hammer, using the
10.5 If the bulk density of the soil or soil-aggregate just
rod guide to ensure the integrity of the hole. The hole shall
measuredbythesoilpermittivityprobeisknown(forexample,
extend a minimum of 25 mm below the end of the probe and
the device to which the soil permittivity probe is connected is
of an alignment that insertion of the probe will not cause the
a device capable of measuring soil or soil-aggregate bulk
probe to tilt from the plane of the prepared area.
density),thenthedrydensityofthismaterialmaybecalculated
as:
9.4 Remove the hole-forming device carefully to prevent
the distortion of the hole, damage to the surface, or loose ρ 5ρ 2 Mw (2)
d t
material from falling into the hole.
where ρ is the bulk density of the material and ρd is the dry
t
9.4.1 When preparing an access hole in granular soils, care
density of the material.
shall be taken in the preparation of the access hole; measure-
ments have the potential to be affected by changes to the
10.6 Likewise, if the bulk density of the soil or soil-
density of surrounding material during the hole formation. aggregate just measured by the soil permittivity probe is
known, then the water content of the material may be calcu-
9.5 Carefully lower the soil permittivity probe into access
lated as:
hole until the surface plate makes full contact with the soil
Mw
surface. Be careful to avoid excessive twisting motion while
ω 5 100· (3)
pushingdownwardwiththehandlestoavoidanysheardamage ρ
d
D8153 − 22
where ω is the water content of the soil (expressed as a 12.1.1.1 Repeatability can be interpreted as maximum dif-
percent). ference between two results, obtained under repeatability
conditions, that is accepted as plausible due to random causes
10.7 Record the water mass per unit volume value to the
3 under normal and correct operation of the test method.
nearest 1 kg/m .
12.1.1.2 Repeatability limits are listed in Table 1.
11. Report: Test Data Sheet(s)/Form(s)
12.1.2 Reproducibility (R)—The difference between two
single and independent results obtained by different operators
11.1 The methodology used to specify how data are re-
applying the same test method in different laboratories using
corded on the test data sheet(s)/form(s), as given below, is
different apparatus on identical test material would, in the long
covered in 1.5.
run, in the normal and correct operation of the test method,
11.2 Record at a minimum the following general informa-
exceed the following values only in one case in 20.
tion (data):
12.1.2.1 Reproducibility can be interpreted as maximum
11.2.1 Test number or test identification.
difference between two results, obtained under reproducibility
11.2.2 Test date/time
conditions, that is accepted as plausible due to random causes
11.2.3 Locationoftest(forexample,StationnumberorGPS
under normal and correct operation of the test method.
or Coordinates or other identifiable information).
12.1.2.2 Reproducibility limits are listed in Table 1.
11.2.4 Visual description of material tested.
12.1.3 The above terms (repeatability limit and reproduc-
11.2.5 Lift number or elevation or depth.
ibility limit) are used as specified in Practice E177.
11.2.6 Name of the operator(s).
12.1.4 Any judgment in accordance with statements 12.1.1
11.2.7 Make, model and serial number of the soil permit-
and 12.1.2 would have an approximate 95% probability of
tivity probe.
being correct.
11.2.8 Water mass per unit volume value in kg/m .
12.2 Bias—At the time of the study, there was no accepted
11.3 The sensitivity of the measurement values listed in
referencematerialsuitablefordeterminingthebiasforthistest
reporting and records are described in 10.4.
method, therefore no statement on bias is being made.
12. Precision and Bias
12.3 The precision statement was determined through sta-
12.1 The precision of this test method is based on an tistical examination of three replicate results, from ten
laboratories, on three materials.These three materials were the
interlaboratory study ILS 1339, “Standard Test Method for
In-Place Bulk Density of Soil and Soil-Aggregate by a Low following, as listed in Table 1, and described in accordance
with Practices D2487 and D2488:
Activity Nuclear Method (Shallow Depth) and In-Place Water
Mass Per Unit Volume of Soil and Soil-Aggregate by Permit- Material 1: SC – Coarse graded clayey sand with fines, 1%
tivity Method (Shallow Depth),” conducted in 2017. Ten gravel, 2% coarse sand, 28% medium sand, 44% fine sand,
laboratories tested three materials with three replicate readings 25% fines, liquid limit = 32, plastic index = 13
on each material. Every “test result” represents an individual Material 2: SC – Coarse graded clayey sand with fines, 2%
determination. Practice E691 was followed for the design and
gravel, 6% coarse sand, 24% medium sand, 27% fine sand,
analysis of the data. 41% fines, liquid limit = 42, plastic index = 20
12.1.1 Repeatability (r)—The difference between repetitive
Material3:Poorlygradedgravelwithsilt,52%gravel,13%
results obtained by the same operator in a given laboratory
coarse sand, 15% medium sand,13% fine sand, 7% fines.
applying the same test method with the same apparatus under
12.4 To judge the equivalency of two test results, it is
constant operating conditions on identical test material within
recommended to choose the soil type closest in characteristics
shortintervalsoftimewouldinthelongrun,inthenormaland
to the test soil.
correct operation of the test method, exceed the following
values only in one case in 20.
13. Measurement Uncertainty
13.1 Information on the measurement uncertainty for this
Supporting data have been filed atASTM International Headquarters and may
test method, and guidance on developing estimated
beobtainedbyrequestingResearchReportRR:D18-2001.ContactASTMCustomer
uncertainties, are described in detail in Appendix X2.
Service at service@astm.org.
TABLE 1 Results of Statistical Analysis (Water Mass Per Unit Volume)
Material Average kg/m Repeatability Standard Reproducibility Standard Repeatability Limit kg/ Reproducibility Limit kg/
3A 3A 3B 3B
Deviation kg/m Deviation kg/m m m
x¯S S rR
r R
1 138 5 8 13 24
2 289 10 11 28 31
3816 918 25
A
The number of significant digits and decimal places presented are representative of the input data. In accordance with Practice D6026, the standard deviation and
acceptable range of results cannot have more decimal places than the input data.
B
Acceptable range of two results is referred to as the d2s limit. It is calculated as 1.960=2c1s, as defined by Practice E177. The difference between two properly conducted
tests should not exceed this limit. The number of significant digits and decimal places presented are equal to that prescribed by this standard or Practice D6026. In addition,
the presented value can have the same number of decimal places as the standard deviation, even if that result has more significant digits than the standard deviation.
D8153 − 22
13.2 Appendix X2 provides examples of measurement un- 14. Keywords
certainty calculations based on results obtained by the manu-
14.1 dielectric constant; dielectric permittivity; permittivity
facturer while carrying out the test method. These tests were
probe;soilwatercontent;volumetricwatercontent;watermass
conductedonthethreematerialsdescribedintheprecisionand
per unit volume
bias study for this test method, and for all-purpose sand that
may be obtained in most hardware stores.
ANNEX
(Mandatory Information)
A1. CALIBRATION, VERIFICATION, AND ADJUSTMENT
A1.1 Permittivity probes shall have calibration equations A1.6.2 Assignment of water mass per unit volume equiva-
formulated initially and after any repairs that can affect the lence to a capacitance standard is done in two basic steps:
existingcalibration.Theinitialcalibration,andanysubsequent
A1.6.2.1 A reference probe, which is a typical permittivity
calibrations, shall consist of curves, tables, or equivalent
probe that is reserved for such purposes, undergoes a soil-
coefficients that correlate the independent variable, soil water
specific calibration process on a given soil, as described in
mass per unit volume, to the dependent variable, probe
A1.7.
oscillator frequency output.
A1.6.2.2 The reference probe is then inserted in or attached
A1.2 Because different soils can have different dielectric
to the capacitance standard in the appropriate measurement
constant properties, it is possible for different soils with the
configuration, and a measurement is acquired. The water mass
same water mass per unit volume value to have different probe
per unit volume measured by the reference probe is then
responses. Consequently, a probe may require a variety of
assigned to the capacitance standard for that particular soil
different soil-specific calibration equations for field use if it is
type, as well as an uncertainty for this assigned value.
used in a variety of different soil types.
A1.6.2.3 A given capacitance standard will have only one
assigned water mass per unit volume equivalence for a given
A1.3 Calibrations for a specific soil shall cover the entire
soil type. However, if the standard is used for different
water mass per unit volume range that one would realistically
calibrations of different soil types, it may have a unique
encounter in a field application.
assigned water mass per unit volume equivalence for each of
A1.4 Initial probe calibrations are generally conducted us-
these different calibrations.
ing mechanically and electrically stable, engineered, non-soil
A1.6.3 For the initial calibration of the permittivity probe,
capacitance standards
theprobeisinsertedinorattachedtoeachcapacitancestandard
A1.5 Calibration of the permittivity probe using non-soil
in the appropriate measurement configuration.Twenty seconds
capacitance standards: the initial calibration of the probe after
of oscillator frequency readings are taken with the probe,
manufacture or extensive repair shall be performed on capaci-
averaged, and recorded.
tance standards, which are non-soil fixtures that can: (1)
A1.6.4 Once the oscillator frequency response data have
accommodate the probe in a consistent, repeatable manner and
(2) present the probe with a consistent, repeatable dielectric been collected with the probe for each capacitance standard,
permittivity value. The repeatability of oscillator frequency calibration functions (curves) are computed.Aunique calibra-
outputineachcapacitancestandardshallbeestablishedpriorto
tion function is computed for each soil type for which the
its use as a calibration standard.
capacitance standards have been assigned water mass per unit
volume equivalence.
A1.6 Thestandardsattachtothepermittivityprobewithtwo
clips,withoneclipattacheddirectlyabovethedielectricspacer
NOTE A1.1—The initial calibration of the permittivity probe generally
to the top conductor, and the other clip attached directly below focuses upon a broad range of soil types, each with a separate and unique
calibration.Three soil types, including one gravel, one sand, and one clay
the dielectric spacer to the bottom conductor. See Fig. A1.1.
have been proven to be successful at properly characterizing the probe
A1.6.1 Each capacitance standard shall have a water mass
response in typical field use.
per unit value equivalence assigned to it prior to its use as a
A1.6.5 The calibration curve for a particular soil type is
calibration standard. The uncertainty of this water mass per
denoted as follows:
unit equivalence value shall be established prior to its use as a
calibration standard. Mw 5 f~D! (A1.1)
D8153 − 22
FIG. A1.1 Capacitance Standard, Drawn to Scale: (1) indicates the metal clips, and (2) indicates the PCB board. Best practice is to slide
the clip onto the probe rather that pressing it onto the probe to avoid damage to the board.
where: A1.6.10.2 Water mass per unit volume equivalence of all
standards for all soil type calibrations encompassed in the
Mw = water mass per unit volume, kg/m ,
calibration activity.
D = oscillator frequency output,
f(D) = the calibration function relating oscillator frequency
A1.6.10.3 Probe oscillator frequency output in each stan-
outputtowatermassperunitvolume.Thisfunctionis dard.
typicallylinearovertherangeofpracticallyobserved
A1.6.10.4 Date and location of the calibration, and identi-
water contents for a particular soil.
fication of the person performing the calibration.
A1.6.10.5 Estimated measurement uncertainties of the
A1.6.6 Once a calibration equation has been established for
probe for each soil type calibration encompassed in the
the probe in this manner, the equation must be verified.
calibration activity.
A1.6.7 Probe verification is achieved when the probe water
A1.6.10.6 Uncertainties of the standards.
mass per unit volume response is found to be within 16 kg/m
A1.6.10.7 Probe calibration equations.
on the capacitance standards on which the probe was
A1.6.10.8 Verification results.
calibrated, for each calibration function included in the cali-
bration process. A1.6.11 Reestablish or verify the assigned water mass per
unit volume equivalence values of the capacitance standards at
A1.6.8 This calibration process may be done by the probe
periods that shall be recommended by the manufacturer.
manufacturer, the user, or an independent laboratory.
A1.7 Calibration Equation Computation of the Permittivity
A1.6.9 For each calibration performed on capacitance
standards, the estimated measurement uncertainty of the probe Probe Using Laboratory-prepared Soil Specimens—Rather
than using capacitive standards as described in A1.5 to
shall be computed, based on probe measurement repeatability
on the standards and the uncertainty in the water mass per unit generate the calibration equation for the probe, one can use
multiple soil specimens of known and varying water contents
volume equivalence value of these standards.
packed into sturdy, non-metallic cylindrical containers. This
A1.6.10 Probe calibration results shall be formally recorded
container shall, at a minimum, have a height of 305 mm and a
and documented in the form of a calibration report, where the
diameter of 305 mm.
following shall be recorded:
A1.6.10.1 Unique identification of the probe and the stan- A1.7.1 Prepare a container of compacted material with a
dards used in its calibration. water content determined by the oven dry method (Test
D8153 − 22
MethodsD2216)andawetdensitycalculatedfromthemassof A1.8.4.1 Take a measurement with the soil permittivity
the material and the inside dimensions of the container. The probe, recording the oscillator frequency output.
container shall not be metallic, as metal can affect probe
A1.8.4.2 Carefullyremovetheprobefromthesoilspecimen
readings.Thewatermassperunitvolumevalueofthesoilmay
in the manner described in 9.7.
be calculated as follows:
A1.8.5 Use the mean value of the replicate readings as the
ρ 3ω
t calibration point value for each test site, calculating the water
Mw 5 (A1.2)
1001ω
mass per unit volume value for each reading using Eq A1.2.
where:
A1.8.6 Once the oscillator frequency response data have
Mw = water mass per unit volume of the soil, kg/m , been collected with the probe for each soil specimen reading,
ω = water content of the soil, percent of dry mass,
calibration functions (curves) are computed in the form of a
ρ = wet density (bulk density) of the soil, kg/m .
t calibration curve as described in Eq A1.1.
A1.7.2 Prepare the soil surface and drill or punch an access
A1.9 Field moisture content adjustment: the calibration
hole in the soil specimen in the manner described in 9.1
equation to be used on a soil must be checked prior to
through 9.5.
performing tests on materials that are distinctly different from
material types previously used in obtaining or adjusting the
A1.7.3 Takeameasurementwiththesoilpermittivityprobe,
calibration that will be used on this material.
recording the oscillator frequency output.
A1.9.1 Sample materials may be selected by either A1.7 or
A1.7.4 Carefully remove the probe from the soil specimen
A1.8. The water content of this sample shall be within 62%
in the manner described in 9.7.
ofthewatercontentestablishedasoptimumforcompactionfor
A1.7.5 Obtain and measure the mass of a portion of the soil
these materials. If A1.7 is selected as the adjustment method:
specimen,nolessthan0.5kginmass,takenclosetowherethe
A1.9.1.1 Asampleofthematerialtakenfromthetestsite,at
dielectric spacer of the probe was located during the preceding
least 0.025 m in volume, shall be compacted into the mea-
probe reading.
surement container, then the specimen shall be measured for
A1.7.6 Oven dry the soil portion obtained in A1.6.5 as water mass per unit volume and bulk (wet), as described in
describedinTestMethodsD2216toobtainthewatercontentof A1.6.1.
the soil.
A1.9.1.2 Prepare the soil surface and drill or punch an
access hole in the soil specimen in the manner described in 9.1
A1.7.7 Perform A1.7.1 through A1.7.6 until a minimum of
through 9.5.
three compacted soil specimens have been measured with
A1.9.1.3 Take a measurement with the soil permittivity
differing water contents that conform to the requirements of
probe, recording the probe water mass per unit volume
A1.3.
response.
A1.7.8 Once the oscillator frequency response data have
A1.9.1.4 Carefullyremovetheprobefromthesoilspecimen
been collected with the probe for each soil specimen reading,
in the manner described in 9.7.
calibration functions (curves) are computed in the form of a
A1.9.1.5 The adjustment factor for this field moisture ad-
calibration curve as described in Eq A1.1.
justment is the difference between the water mass per unit
volume computed in A1.9.1.1 (using Eq A1.2) and the water
A1.8 Calibration equation computation of the permittivity
mass per unit volume measured in A1.9.1.3.
probe in the field: where neither of the calibration methods
described in A1.6 or A1.7 is available, the probe may be
A1.9.2 If the material is selected by A1.8, the following
calibrated by using a minimum of three selected test sites in an
offset calculation procedure is performed:
areaofacompactionprojectwherematerialhasbeenplacedat
A1.9.2.1 Select the field test site that conforms to the water
several different water contents.
content requirement described in A1.9.1.
A1.9.2.2 Measure the field test site for water mass per unit
A1.8.1 The test sites shall represent the range of water
volume and bulk (wet) density as described in A1.8.3.
contents over which the calibration equation is to be used.
A1.9.2.3 Prepare the soil surface and drill or punch an
A1.8.2 At least three replicate probe measurements shall be
access hole in the soil specimen in the manner described in 9.1
made at each test site.
through 9.5.
A1.8.3 The bulk (wet) density at each site shall be deter-
A1.9.2.4 Take a measurement with the soil permittivity
mined by measurements with calibrated equipment in accor-
probe, recording the probe water mass per unit volume
dance with the procedures described in Test Methods D1556/
response.
D1556M, D2167, D2937, D6938,or D8167/D8167M. The
A1.9.2.5 Carefullyremovetheprobefromthesoilspecimen
water content of the material at each of the test sites shall be
in the manner described in 9.7.
determined using Test Methods D2216.
A1.9.2.6 Perform A1.9.2.1 through A1.9.2.5 a minimum of
three times
A1.8.4 Foreachprobereading,preparethesoilsurface,drill
or punch an access hole in the soil, and install the probe in the A1.9.2.7 Afterthefinalfieldreadingisdone,averageallthe
specimen in the manner described in 9.1 through 9.5. water mass per unit volume readings recorded in A1.9.2.4.
D8153 − 22
A1.9.2.8 The adjustment factor for this field moisture ad- equipment used in the calibration process, as well as the
justment is the difference between the water mass per unit properties of the material for which the calibration is being
volume computed in A1.9.2.2 (using EqA1.2) and the average
performed. Appendix X2 provides an example for creating an
water mass per unit volume computed in A1.9.2.7.
uncertainty budget for the probe measurements related to the
calibration process.
A1.9.3 This device generally has a provision to implement
the adjustment factor where the user is lead through the
necessary steps.
A1.10 Estimated Measurement Uncertainties—Each step in
the calibration process introduces measurement uncertainties.
These uncertainties are directly related to the processes and
APPENDIXES
(Nonmandatory Information)
X1. DATA SHEETS/FORMS
X1.1 See Fig. X1.1.
D8153 − 22
FIG. X1.1 Example Data Form—Soil Permittivity Probe
D8153 − 22
X2. ESTIMATED MEASUREMENT UNCERTAINTY BUDGET: EXAMPLE
X2.1 Thecalibration,verification,andadjustmentprocesses
D = the nominal density of the water used to fill the
w
described in AnnexA1 all have inherent associated uncertain-
container,
ties. These uncertainties propagate throughout the measure-
Mw = the nominal mass of the water required to fill the
ments and calculations from the first measurements of the
container,
calibration to the final estimated measurement uncertainty of
u = the combined standard uncertainty of the water
D
w
the probe reading at a test site. density,
u = the combined standard uncertainty from volume mea-
s
X2.2 The purpose of this appendix is to identify and to
surement variability.
estimate sources of uncertainty in the calibration, verification,
X2.4.5 Dw, the density of water, is dependent of its tem-
and adjustment of the probe for four example soil types.
perature. The formula relating water temperature to density is
known as Kell’s Formulations:
X2.3 The uncertainty values described herein are estimates
25 26 2
based upon tests conducted by the device manufacturer; the
f t 5 0.9998530816.32693 310 t 2 8.523829 310 t 16.943248
~ !
actual values obtained by the user are dependent on the
28 3 210 4
310 t 2 3.821216 310 t (X2.2)
competence of the personnel performing the testing, the
where:
quantity of data acquired, and the suitability of the equipment
and facilities used. It is neither appropriate for, nor the t = the temperature and
f(t) = the water density at this temperature.
responsibilityof,thetestmethodtoprovideexplicitvaluesthat
auserwouldquoteastheirestimateofuncertainty.Uncertainty
For this formula, the temperature is expressed in degrees
values must be based on data generated by a laboratory
Celsius and the density in grams per cubic centimeter.
reporting results using the test method.
X2.4.6 The uncertainty of the water density is computed by
the propagation of uncertainty formula, where the function is
X2.4 Calculation of the calibration equation of the permit-
Eq X2.3:
tivity probe using laboratory prepared soil specimens: Speci-
men volume uncertainty: The volume of the container that the
δf t
~ !
2 2 2
u 5 u 1u (X2.3)
S D
D T d
soil specimens of various water contents are compacted into w
δt
mustbedetermined.Thisvalue,combinedwiththemassofthe
where:
soil, will provide the wet density of the soil specimen under
uT = the combined standard uncertainty of the temperature
measurement.
measured in the water and
X2.4.1 The container volume is determined using a method
ud = the combined standard uncertainty of the Kell formula.
similar to that used in Test Method C231/C231M to determine
6 3
According to NIST the value of ud is 0.0070 kg/m .
the volume of the measuring bowl: the container is filled with
water, and one slides a glass plate carefully over the flange of X2.4.7 For the example described in this appendix a nomi-
the container in a manner to ensure that the container is naltemperaturevalueof20°Cwillbeused,withthecombined
completely filled with water. standard uncertainty of the device used to measure the water
temperature set to 0.1°C. The result is a U value of 0.029
D
X2.4.2 Once the glass plate is in place, the filled container w
kg/m .
and plate are weighted, and the weight of the plate and empty
container are subtracted to obtain the mass of the water. X2.4.8 The uncertainty of the mass of water required to fill
Multiple determinations are recommended. the container is equivalent to the combined standard uncer-
tainty of the scale used to measure the water mass. For the
X2.4.3 The water temperature shall be measured so that an
exampledescribedinthisappendix,afloorscalewasusedwith
accurate determination of the water density can be made.
a combined standard uncertainty in its measurements of 0.017
X2.4.4 Thevolumeofthecontaineristhemassofthewater
kilograms.
requiredtofillthecontainerdividedbythedensityofthewater.
X2.4.9 Fortheexampledescribedinthisappendixatotalof
The uncertainty in this volume is expressed as:
thirty of the measurements described in X2.4.1 – X2.4.3 with
u
2M
M
w w
2 2 the container volume calculated each time based on the mass
u 5 1 u (X2.1)
2 S 2 D
v D 1u
D D w s
w w determination and the density of the water. The nominal
measured volume was 0.0237 cubic meters with a standard
where:
–5
deviation of 2.38×10 cubic meters.
u = the combined standard uncertainty of the container
V
volume,
u = the combined standard uncertainty of the mass of the
M
w
“ITS-90 Density of Water Formulation for Volumetric Standards Calibration.”
water required to fill the container,
Journal of Research of the National Institute of Standards and Technology, Volume
9, Number 3, May-June 1992. Page 336.
NIST SOP 29 Job Aid, “Uncertainty Budget Table Examples”, page 8.
ASTM Form and Style Manual, April 2020 Edition, A22.2 September 2014.
D8153 − 22
X2.4.10 Since the average of the thirty volume readings men water content—The water content of the soil specimen,
would be used as the final volume of the container, one would and its uncertainty, must be determined in order ultimately to
use the Central Limit Theorem to compute a us value of
determine the water mass per unit volume of the specimen.
–5 2 –6
√((2.38×10 ) ÷30) = 4.34×10 cubic meters.
X2.6.1 The (gravimetric) water content of the soil
X2.4.11 For the example described in this appendix the
specimen, denoted by ω and expressed as a percent, is
nominal mass of water required to fill the container was 23.7
calculated by dividing the mass of the water in the soil by the
kilograms, with a nominal density of 1.01×10 kilograms per
mass of the dry soil of the specimen, as described in Test
cubic meter.
Methods D2216.
X2.4.12 Combining all the terms in Eq X2.1 results in a
X2.6.2 The uncertainty of the water content is computed by
final combined standard uncertainty in the volume of the
the propagation of uncertainty formula, where the function is
container in the example described in this appendix of
–5
Eq X2.5:
3.1×10 cubic meters.
2 2 2
~2u ! ~2u ! ~M 2 M !
ls ls ws ds
2 2
u 5 100 1 (X2.5)
X2.5 Calcula
...