Skip to contentUnited States Department of Transportation - Federal Highway Administration FHWA Home
Research Home   |   Pavements Home
REPORT
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-HRT-07-040
Date: October 2011

 

Falling Weight Deflectometer Calibration Center and Operational Improvements: Redevelopment of The Calibration Protocol and Equipment

APPENDIX C. PDDX STANDARD VERSION 2.0

INTRODUCTION

The purpose of the AASHTO PDDX standard is to foster a uniform file format for output from all types of pavement deflection devices, including FWDs. A harmonized file format allows programmers to develop deflection data analysis programs without the need to provide file readers for the many different native file formats that have been promulgated by equipment manufacturers over time.

While the purpose of this specification is to define a harmonized data format, it is not intended to replace the native file formats of the various manufacturers. Both formats can be provided if the manufacturer chooses. Equipment owners have the option to choose the desired output file format. The PDDX format can be used for static, steady-state vibratory, and dynamic pulse-loading devices, although the primary focus of the Version 2.0 standard is for pulse-loading devices (i.e., FWDs).

The PDDX format puts related data items into sections with descriptive names. It is similar to the .INI format used in Windows®-based configuration files. Each line in the file can either be a section heading or a data entry field with one or more values.

PDDX VERSION 2.0 OVERVIEW

Version 2.0 of the PDDX standard incorporates a few changes from Version 1.0. It reconciles the minor differences that have evolved between the PDDX standard and the input data needs of the AASHTO DARWin pavement design program. DARWin can read PDDX Version 2.0 files. The new version also adds a few data items that were inadvertently left out of Version 1.0. It was necessary to change the name of some data items from Version 1.0, which may require updating PDDX file readers.

The following three types of file formats are described in detail below:

The PDDX file format is used for reporting the results of routine FWD testing of roads and airfields. This format provides data that is collected at multiple test points in a line or a grid pattern.

The FWD calibration record file format contains a historical record of the last calibration that was performed on the FWD. This may be an annual calibration possibly supplemented by monthly calibrations. The file contains information on the date and location where the calibration was performed. It also identifies the special equipment that was used in the calibration. Some sections from the PDDX file format are included in the calibration history file.

Two FWD calibration data exchange file formats are provided. One file is created by the FWD computer and provides information that is needed to begin performing an annual calibration. The data are transferred electronically from the FWD computer to the calibration center computer.

The second file contains the results of the calibration that can be transferred electronically from the calibration center computer to the FWD computer. Both of these files require the cooperation of the FWD manufacturers to provide a means for writing the first file and reading the second one.

Description of Each Data Section and Data Entry Lines

As discussed previously, the data format has a modular structure. Data elements of similar characteristics are grouped together in individual sections. The first line is the section descriptor contained in brackets. Each module contains a number of data items with its associated value or values. Both the added data items and the renamed data items have been identified in the descriptions in bold type.

STANDARD PDDX FILE FORMAT

Pavement Deflection Data Exchange File Section

This should be the initial section in the file. It identifies information related to the PDDX format or version that is being used.

Section
     Descriptor [Pavement Deflection Data Exchange File]

PDDX Version Number

Syntax: PDDXVersionNumber = number
Description: This entry denotes the current PDDX format version. Depending on the nature and scope of future revisions, the version number of PDDX may change. This is provided to allow for possible changes in the PDDX Standard in the future.
Example: PDDXVersionNumber = 2.0

Delimiter Symbol

Syntax: DelimiterSymbol = string
Description:  A single American Standard Code for Information Interchange (ASCII) printable non-white space character denoting the delimiter symbol. The recommended delimiter symbols include the comma (ASCII character 44), exclamation mark (ASCII character 33), and concatenation symbol (ASCII character 124).
Example: DelimiterSymbol = ,
Note: The delimiter symbol and the decimal symbol entries must be mutually exclusive. In the United States, the usual delimiter is the comma, and the usual decimal symbol is the period.

Decimal Symbol

Syntax: DecimalSymbol = string
Description: A single ASCII printable non-white space character denoting the decimal symbol. The internationally accepted decimal symbols include ASCII characters 44 (comma) and 46 (period).
Example: Decimal Symbol = .
Note: The decimal symbol and the delimiter symbol entries must be mutually exclusive. In the United States, the usual delimiter is the comma, and the usual decimal symbol is the period.

Operations Information Section

This section contains general information recorded once for informational purposes. These data are not used in the analysis of the deflection data; however, they may aid engineers with respect to data analysis by recording time of day and other pertinent information.

Section
     Descriptor [Operations Information]

File Name

Syntax: FileName = string
Description: This entry identifies the directory location and filename of the PDDX file where   the deflection testing data are stored.
Example: FileName = C:\FWD\DATA\SAMPLE.DDX


Software Version

Syntax: SoftwareVersion = string
Description: This entry identifies the software version of the FWD operational software.
Example: SoftwareVersion = 18.9
Note: This is used by the LTPP database to identify which version of the field program is used to collect the data from FWD. This data field is not in the PDDX standard Version 1.0.


Start Date

Syntax: StartDate = date
Description: Date at onset of testing in dd-mmm-yyyy date format.
Example: StartDate = 28-Apr-2009


Start Time

Syntax: StartTime = time
Description: Time at the onset of testing in hour:minute:second in 24-h clock format.
Example: StartTime = 07:41:18


End Date

Syntax: EndDate = date
Description: Date at completion of testing in dd-mmm-yyyy date format.
Example: EndDate = 29-Apr-2009


End Time

Syntax: EndTime = time
Description: Time at completion of testing in hour:minute:second 24-h clock format.
Example: EndTime = 15:24:12


Operator Name

Syntax: OperatorName = string
Description: Name of deflection device operator.
Example: OperatorName = Joe Smith


Weather Condition

Syntax: WeatherCondition = string
Description: General description of weather conditions at testing site (e.g., sunny, cloudy, raining).
Example: WeatherCondition = sunny


Units Section

This section contains information regarding the units system. All units applicable to the PDDX file format are described in this section. Some units that are unique to FWD calibration are listed in the other file formats.

Note that all units are listed in singular format. English and metric units for applicable data are summarized in table 10. All units used in one PDDX file must be of the same system of units. Thus, a file must use only metric or English measurements. Also, only one unit identifier per data element is allowed for each entry. All permissible unit identifiers are defined below and are case-insensitive.

Table 10. Unit systems for English and metric PDDX files.1
Parameter English System Units Metric System Units
Length Mil Micron
  Inch Millimeter
  Foot Centimeter
  Yard Meter
  Mile Kilometer
Mass Pound Kilogram
Time Second Second
Force Pound-force KiloNewton
Kilopound-force Kilogram-force
Pressure Pound-force per square inch KiloPascal
Temperature Fahrenheit Celsius
Frequency Hertz Hertz
Angle Degree-minute-second Degree-minute-second

1Some of the strings in the table are modified slightly from Version 1.0.

Section
     Descriptor [Units]

Load Plate Radius Units

Syntax: LoadPlateRadiusUnits = string
Description: The units to be used to identify the radius of the load plate on an impulse load deflection device. The common units of measurement are inches and millimeters.
Example: LoadPlateRadiusUnits = inch

Load Units

Syntax: LoadUnits = string
Description: Units used to measure the magnitude of the applied load (force or pressure) in pound-force, Newton, kiloPascal, or pound-force per square inch. Data with a different unit than the one chosen during calibration setup is converted based upon this data field.
Example: LoadUnits = pound-force

Deflection Units

Syntax: DeflectionUnits = string
Description: Unit used to measure the magnitude of the pavement surface deflection. All deflection sensors must use the deflection unit specified by this entry. The typical units of measurement are mils or microns. Data with a different unit than the one chosen during calibration setup is converted based upon this data field.
Example: DeflectionUnits = mil

Temperature Units

Syntax: TemperatureUnits = string
Description: Unit used to measure temperature data. All temperature sensors must use the temperature unit specified by this entry.
Example: TemperatureUnits = Fahrenheit


Sensors Location Units

Syntax: SensorsLocationUnits = string
Description: Units used to measure the longitudinal and transverse coordinates of deflection sensors with respect to the center of the load plate.
Example: SensorsLocationUnits = inch


GPS Units

Syntax: GPSUnits = string, string, string
Description: Units used to measure global position using a global positioning system (GPS) device. Each GPS unit should be separated by the delimiter symbol.
Example: GPSUnits = degree-minute-second, degree-minute-second, foot


Test Location Units

Syntax: TestLocationUnits = string, string, string
Description: Units used to measure test location distances in an x, y, z coordinate system, with z denoting elevation. Common units are mile, foot, kilometer, and meter. Each test location unit should be separated by the delimiter symbol.
Example: TestLocationUnits = mile, foot, foot


Nominal Test Spacing Units

Syntax: NominalTestSpacingUnits = string
Description: Units used to measure the nominal spacing between test points.
Example: NominalTestSpacingUnits = foot


Load Frequency Units

Syntax: LoadFrequencyUnits = string
Description: Units used to measure the loading frequency of vibratory loading devices.
Example: LoadFrequencyUnits = Hertz


Drop History Data Frequency Unit

Syntax: DropHistoryDataFrequencyUnits = string
Description: Units used to measure the drop history data sampling rate.
Example: DropHistoryDataFrequencyUnits = Hertz


Joint Crack Width Units

Syntax: JointCrackWidthUnits = string
Description: Units used to measure the width of a joint or a crack.
Example: JointCrackWidthUnits = millimeter
Note: This data field is not in the PDDX standard Version 1.0.


Device Information Section

This section contains information regarding the deflection device type, name, and model. Other entries include serial numbers for the overall device, the load plate, and the deflection sensors.

Section
     Descriptor [Device Information]

Device Designation Name

Syntax: DeviceDesignationName = string
Description: The name of the deflection device being used for testing.
Example: DeviceDesignationName = KUAB 2m-FWD


Device Model Number

Syntax: DeviceModelNumber = string
Description: The model designation for the deflection device being used for testing.
Example: DeviceModelNumber = 8714


Device Serial Number

Syntax: DeviceSerialNumber = string
Description: The serial number of the deflection device being used for testing.
Example: DeviceSerialNumber = 245


Load Cell Serial Number

Syntax: LoadCellSerialNumber = string
Description: The serial number of the load cell being used for testing.
Example: LoadCellSerialNumber = LC132

 

Sensor Serial Numbers

Syntax: SensorSerialNumbers = string(s)
Description: The serial numbers of each of the deflection sensors being used for testing listed in the same order as the x-axis distances defined in the device configuration section. Each serial number should be separated by the delimiter symbol.
Example: SensorSerialNumbers = 30829, 30830, 30831, 30890, 30832, 30796, 30864

Device Load Type

Syntax: DeviceLoadType = string
Description: The type of loading device being used for testing (static, vibratory, impulse, or rolling).
Example: DeviceLoadType = Impulse



Device Configuration Section

This section contains information regarding the exact configuration of the deflection device at the time of testing. Figure 41 provides an illustration of a typical load cell and deflection sensor configuration.

Figure. 41. Illustration. Typical load cell and deflection sensor configuration. This illustration shows an overhead view of a typical load cell and deflection sensors configuration. The sensors are labeled in an x, y notation, where x is distance from the load plate as measured forward down the road and y is the distance from the load plate as measured to the left when facing down the road. The load cell is positioned at 0, 0, and the other measurements to the right of the load cell include 12, 0; 24, 0; 36, 0; 48, 0; 60, 0; and 72, 0. The second sensor is the deflection measuring sensor.

Figure 41. Illustration. Typical load cell and deflection sensor configuration.

Section
     Descriptor [Device Configuration]

Load Plate Radius

Syntax: LoadPlateRadius = number
Description: Radius of the load plate used during testing. Enter the radius in the units that have been previously specified.
Example: LoadPlateRadius = 5.91


Number of Deflection Sensors

Syntax: NumberOfDeflectionSensors = number
Description: This entry denotes the number of deflection measuring sensors that are being used for collection of deflection data.
Example: NumberOfDeflectionSensors = 9


Deflection Sensor X-Axis Distances

Syntax: DeflectionSensorXAxisDistances = number(s)
Description: This entry denotes the x-coordinate of each deflection sensor with respect to the center of the load plate. The x-direction is typically measured in the direction in which the deflection device is traveling. Negative distances are behind the load plate.
Example: DeflectionSensorXAxisDistances = 0, 12, 24, 36, 48, 60, 72, -12, 0
Note: Generally, FWD collects data in the order of the data acquisition channels. Therefore, the x and y distances should correspond to the arrangement in which the deflection sensors are connected to the data acquisition channels. Thus, if channel 1 corresponds to the sensor in position (0,0) and channel 2 corresponds to position (12,0), they should be listed in that order.

Deflection Sensor Y-Axis Distances

Syntax: DeflectionSensorYAxisDistances = number(s)
Description: This entry denotes the y-coordinate of each deflection sensor with respect to the center of the load plate. The y-direction is typically perpendicular to the direction in which the deflection device is traveling. Negative distances are to the right of the load plate.
Example: DeflectionSensorYAxisDistances = 0, 0, 0, 0, 0, 0, 0, 0, -12
Note: Generally, FWD collects data in the order of the data acquisition channels. Therefore, the x and y distances should correspond to the arrangement in which the deflection sensors are connected to the data acquisition channels. Thus, if channel 1 corresponds to the sensor in position (0,0) and channel 2 corresponds to position (12,0), they should be listed in that order.

Number of Temperature Sensors

Syntax: NumberOtTemperatureSensors = number
Description: Number of sensors used to collect temperature data.
Example: NumberOtTemperatureSensors = 3


Temperature Sensor Use

Syntax: TemperatureSensorUse = string(s)
Description: Description of the item for which each temperature sensor is recording the temperature at the time of testing. Options for the item description include air, pavement surface, pavement middepth, and pavement bottom.
Example: TemperatureSensorUse = air, surface, middepth

Load Frequency

Syntax: LoadFrequency = number
Description: The loading frequency used for vibratory testing devices. Note that the frequency value should correspond with the previously entered load frequency unit.
Example: LoadFrequency = 25

Device Calibration Section

This section contains information regarding the equipment manufacturer's calibration of the deflection device as well as the results of the most recent annual calibration and monthly calibration. Annual calibration is conducted on FWDs for the load cell and deflection sensors to ensure that all readings are accurate within specified limits.

Section
     Descriptor [Device Calibration]

Load Cell Manufacturer Calibration Date

Syntax: LoadCellManufacturerCalibrationDate = date
Description: Date of the most recent load cell calibration in dd-mmm-yyyy date format.
Example: LoadCellManufacturerCalibrationDate = 27-Sep-1991
Note: This calibration date is the FWD manufacturer’s load cell calibration. Usually done only upon delivery or major work on the machine, it is not the annual calibration date. This field is named load cell calibration date in Version 1.0.

Load Cell Manufacturer Calibration Factor

Syntax: LoadCellManufacturerCalibrationFactor = number
Description: Calibration factor obtained from the most recent calibration of the load plate load cell.
Example: LoadCellManufacturerCalibrationFactor = 10956
Note: This calibration factor is the FWD manufacturer’s calibration. Usually done only    upon delivery or major work on the machine, it is not an annual calibration gain factor. This field is named load cell calibration factor in Version 1.0.

Load Cell Manufacturer Calibration Intercept

Syntax: LoadCellManufacturerCalibrationIntercept = number
Description: The y-intercept of the linear relationship developed for calibration of the load cell.
Example: LoadCellManufacturerCalibrationIntercept = 174
Note: This calibration intercept is the FWD manufacturer’s calibration. Usually done only upon delivery or major work on the machine, it is not the annual calibration factor. This field is named load cell calibration intercept in Version 1.0.

Load Cell Annual Calibration Date

Syntax: LoadCellAnnualCalibrationDate = date
Description: Date of the most recent reference calibration of the FWD load cell in dd-mmm-yyyy date format.
Example: LoadCellAnnualCalibrationDate = 27-Sep-2009
Note: This is the date of the most recent annual calibration of the load cell. This data field is not in the PDDX standard Version 1.0.


Load Cell Annual Calibration Gain

Syntax: LoadCellAnnualCalibrationGain = number
Description: The multiplier that adjusts the measured values from FWD to match the output from the reference load cell.
Example: LoadCellAnnualCalibrationGain = 1.003
Note: This is the final gain factor for the FWD load cell determined by using the annual calibration procedure. This data field is not in the PDDX standard Version 1.0.

Sensor Static Calibration Date

Syntax: SensorStaticCalibrationDate = date
Description: Date of most recent deflection sensors static calibration in dd-mmm-yyyy date format.
Example: SensorStaticCalibrationDate = 27-Apr-1992
Note: The static calibrations are only done with a KUAB FWD. The static calibration of seismometers is performed through the use of a built-in micrometer on the top of each sensor.

Sensor Static Calibration Factors

Syntax: SensorStaticCalibrationFactors = number(s)
Description: Static calibration is conducted for deflection devices utilizing seismic displacement transducers (seismometers) for deflection measurement under a static condition (no pavement loading).
Example: SensorStaticCalibrationFactors = 0.573, 0.553, 0.420, 0.300
Note: The static calibrations are only done with a KUAB FWD. The static calibration of seismometers is performed through the use of a built-in micrometer on the top of each sensor.

Sensor Manufacturer Calibration Date

Syntax: SensorManufacturerCalibrationDate = date
Description: Date of most recent deflection sensors dynamic calibration in dd-mmm-yyyy date format.
Example: SensorManufacturerCalibrationDate = 27-Apr-1992
Note: This is the manufacturer’s deflection sensor calibration date. This field is named sensor dynamic calibration date in Version 1.0.



Sensor Manufacturer Calibration Factors

Syntax: SensorManufacturerCalibrationFactors = number(s)
Description: Dynamic calibration is conducted for deflection devices with seismometers to relate the sensor’s dynamic to static behavior.
Example: SensorManufacturerCalibrationFactors = 1.050, 1.050, 1.050, 1.050
Note: This is the FWD manufacturer’s deflection sensor calibration factor. For example, in the Dynatest® FWD, this is labeled the absolute gain factor. This field is named sensor dynamic calibration factor in Version 1.0.

Sensor Annual Calibration Date

Syntax: SensorAnnualCalibrationDate = date
Description: Date of most recent deflection sensor annual calibration in dd-mmm-yyyy date format.
Example: SensorAnnualCalibrationDate = 27-Apr-2009
Note: This is the date that the deflection sensors were most recently calibrated using the annual calibration procedure. This field is named sensor reference calibration date in Version 1.0.

Sensor Monthly Calibration Date

Syntax: SensorMonthlyCalibrationDate = date
Description: Date of most recent deflection sensor annual calibration in dd-mmm-yyyy date format.
Example: SensorMonthlyCalibrationDate = 27-May-2009
Note: This is the date that the deflection sensors were most recently calibrated using the monthly calibration procedure. This field is named sensor relative calibration date in Version 1.0.

Sensor Calibration Gains

Syntax: SensorCalibrationGains = number(s)
Description: The multiplier that adjusts the measured values from FWD to match the output from the reference accelerometer.
Example: SensorCalibrationGain = 1.006, 1.003, 1.011, 0.998, 1.018, 0.999, 1.001
Note: These are the final gain factors for the deflection sensors using the annual calibration procedure or the most recent monthly calibration procedure. This field is named sensor reference calibration gain in Version 1.0.

DMI Device Calibration Date

Syntax: DMIDeviceCalibrationDate = date
Description: Date of the most recent distance measuring instrument (DMI) device calibration in dd-mmm-yyyy date format.
Example: DMIDeviceCalibrationDate = 27-Sep-2009


DMI Device Calibration Factor

Syntax: DMIDeviceCalibrationFactor = number
Description: Calibration factor obtained for the DMI device.
Example: DMIDeviceCalibrationFactor = 2694.3


Location Identification Section

This section contains information regarding the location and nature of the test site. Basic components of the test site are included such as the geographic location, client, and pavement feature section.

Section
     Descriptor [Location Identification]

Site Name

Syntax: SiteName = string
Description: Location of the project site. For highway testing, provide the name of the State, county, township, or city in which the project is located. On airport projects, provide the name of the airport.
Examples: SiteName = VA, Fairfax County
SiteName = O'Hare International Airport

Facility Name

Syntax: FacilityName = string
Description: Name of pavement facility or system being tested.
Example: FacilityName = Interstate 95
FacilityName = Runway 9L-27R
Note: A facility is a collection of sections that have the same use (e.g., a single runway, street, or parking lot).


Section Name

Syntax: SectionName = string
Description: Name of the pavement section where deflection testing is conducted.
Example: SectionName = Lorton Road to Newington Interchange
SectionName = Section Al
Note: A section is a pavement that has similar cross section, construction history, traffic level, and use that can be treated as a single unit for analysis purposes.

Direction of Travel

Syntax: DirectionOfTravel = string
Description: Indicates the direction of travel during testing.
Example: DirectionOfTravel = Northbound
Note: This is a user-defined entry that may be a compass direction, but it does not need be. Any designation, such as a runway end or street name, may be used to indicate direction of travel.

Pavement Type

Syntax: PavementType = string
Description: Type of pavement being tested (e.g., asphalt concrete (AC), Portland cement concrete (PCC), AC/PCC, flexible, rigid, composite).
Example: PavementType = PCC


Data Configuration Section

This section describes total test points on the project, their spacing, details of the measurements collected at each test point, and other data specific to each test point.

Section
     Descriptor [Deflection Data]

Number of Test Locations

Syntax: NumberOfTestLocations = number
Description: The number of test locations that are included in the current file.
Example: NumberOfTestLocations = 10


Nominal Test Pattern

Syntax: NominalTestPattern = string
Description: The typical test pattern being used for testing—linear for highways and runways or grid for parking lots and aircraft parking aprons.
Example: NorninalTestPattern = linear


Nominal Test Spacing

Syntax: NorninalTestSpacing = number
Description: The typical test spacing being used for testing; a typical test spacing exists in feet, meters, etc.
Example: NorninalTestSpacing = 500


Drop History Data Frequency

Syntax: DropHistoryDataFrequency = number
Description: The rate at which readings are recorded for each sensor being sampled by
the DAQ.
Example: DropHistoryDataFrequency = 10,000


Number of Drop History Data Samples

Syntax: NumberOfDropHistoryDataSamples = number
Description: Total number of readings obtained for each sensor during the recording of each time history.
Example: NumberOfDropHistoryDataSamples = 300


Test Location Section

The test location section indicates the number of current test points where "locationcounter" is an integer starting at 1 and ascending for each test point in the current file. Figure 42 provides an example of a typical test location.

Figure 42. Illustration. Example of a typical test location. This illustration shows the location of a typical test section on a highway, which is drawn horizontally. The direction of testing is to the right. There are two lanes labeled "A" and "B," and lane A is the bottom lane. The beginning of the section is at station 623+00, and subsequent even stations are labeled 624+00 and 625+00. The test point is in the center of lane A at station 625+84.

Figure 42. Illustration. Example of a typical test location.

Section
     Descriptor [Test Location locationcounter]

Example: [Test Location 1]
Note: The maximum number for locationcounter is NumberOfTestLocations. This section will be repeated sequentially for each test location.


Test Location

Syntax: GPSLocation = number, number, number
Description: Global location of the test point in an x, y, z coordinate system.
Example: GPSLocation = 28.345, 74.345, 0


GPS Location

Syntax: GPSLocation = number, number, number
Description: Global location of the test point in an x, y, z coordinate system.
Example: GPSLocation = 28.345, 74.345, 0


Test Lane

Syntax: TestLane = string
Description: Designation of the lane being tested. Test lane layouts are designated at the discretion of the engineer or FWD operator.
Example: TestLane = outside lane, inner wheelpath


Test Type

Syntax: TestType = string
Description: Type of test being performed (e.g., basin, center, edge, corner). The latter three designations would mainly be used on concrete pavements.
Example: TestType = basin


Drop History Type

Syntax: DropHistoryType = string
Description: The type of drop history recorded at the test location (e.g., load only, deflections only, or load and deflections).
Example: DropHistoryType = load and deflections


Test Temperatures

Syntax: TestTemperatures = number(s)
Description: The temperatures measured for the current test point.
Example: TestTemperatures = 60.7, 94.2, 80.5
Note: The measured temperatures are described in the [Device Configuration] section (e.g., air, surface, mid-depth, gradient average).


Test Date

Syntax: TestDate = date
Description: Date at onset of testing in dd-mmm-yyyy date format.
Example: TestDate = 12-Apr-2009


Test Time

Syntax: TestComment = time
Description: Time at the beginning of testing for the current test point in hour:minute:second 24-h clock format.
Example: TestTime = 07:41:18


Test Comment

Syntax: TestComment = string
Description: Any comment regarding the current test point entered manually by the operator.
Example: TestComment = Longitudinal crack


Number of Drops

Syntax: NumberOfDrops = number
Description: The number of load drops made at each test point.
Example: NumberOfDrops = 12


Drop Data

Syntax: DropData_dropcounter = number(s)
Description: The measured peak load and deflections for the current drop, where dropcounter   is the number of the drop in the sequence.
Example: DropData_l = 9194, 4.93, 4.14, 4.01, 3.65, 3.10, 2.50, 2.15
Note: The maximum number for dropcounter is NumberOfDrops.


Drop History Data

Syntax: DropHistoryData_dropcounter_samplecounter = number(s)
Description: The time history load and deflections data for each drop, numbered sequentially as dropcounter_samplecounter. Each entry contains information similar in format to DropData_counterdrop when load and deflection are recorded.
Example: DropHistoryData_1_5 = 1248, 1.15, 1.02, 0.98, 0.87, 0.79, 0.70, 0.62
Note: The maximum number for samplecounter is NumberOfDropHistoryDataSamples

SPECIAL FORMAT FOR FWD CALIBRATION RECORD FILES

At the conclusion of each FWD calibration, WinFWDCal creates a permanent electronic record of the calibration results in DDX file format. The file is named FWDCalibrationRecorddd-mmm-yyyy.DDX (where dd is the date, mmm is the month abbreviation, and yyyy is the year (e.g., 12-Feb-2009)).

The file includes the following sections from the PDDX file format as defined above:

The same file is created for both annual and monthly calibration. When retained together with the FWD and reference system data files, a complete record of the calibration is formed that allows the calibration results to be recreated and reviewed at any time using WinFWDCal.

FWD Calibration Center Information Section

This section includes information about the FWD calibration center personnel and equipment. It is created only for record keeping associated with FWD calibration. This section would not normally be included in the PDDX file format that is used for road and airfield data exchange. In order to be self-contained, some additional units of measurement are defined in this file.

Section
     Descriptor [FWD Calibration Center Information]

Calibration Center

Syntax: CalibrationCenter = string
Description: The name of the FWD calibration center.
Example: CalibrationCenter = Colorado Department of Transportation


Calibration Center ID Code

Syntax: CalCenterIDCode = number
Description: An ID code assigned to each FWD calibration center based upon the order of installation.
Example: CalCenterIDCode = 21


Calibration Center Operator

Syntax: CalibrationCenterOperator = string
Description: Name of the FWD calibration center operator.
Example: CalibrationCenterOperator = Edward Trujillo


Calibration Center Operator Certification Date

Syntax: CalibrationCenterOperatorCertificationDate = date
Description: Date of last FWD calibration center operator certification and QA/QC visit. The certification is valid for 15 months after this date, and recertification must be scheduled within 12 months of this date.
Example: CalibrationCenterOperator = 27-Aug-08

WinFWDCal Version Number

Syntax: WinFWDCalVersionNumber = string
Description: Version number of WinFWDCal software along with the release date.
Example: WinFWDCalVersionNumber = 1.2.702 21 April 2008


Type of Calibration

Syntax: TypeOfCalibration = string
Description: Denotes the type of procedure that was used for the FWD Calibration
(e.g., annual, monthly, or sensor replacement).
Example: TypeOfCalibration = Annual


Signal Conditioner Serial Number

Syntax: SignalConditionerSerialNumber = string
Description: Serial number of signal conditioner used in FWD calibration at a calibration center.
Example: SignalConditionerSerialNumber = 095889


A to D Board Serial Number

Syntax: AtoDBoardSerialNumber = string
Description: Serial number of KUSB A/D board used in FWD calibration at a calibration center.
Example: AtoDBoardSerialNumber = 1142589


Universal Test Machine Name

Syntax: UniversalTestMachineName = string
Description: Name of universal calibration machine used to calibrate the reference load cell.
Example: UniversalTestMachineName = Baldwin Universal Testing Machine UniversalTestMachineSerialNumber = 040-1663


Universal Test Machine Calibration Date

Syntax: UniversalTestMachineCalibrationDate = date
Description: Date of NIST traceable calibration of universal testing machine in dd-mmm-yyyy format.
Example: UniversalTestMachineCalibrationDate = 09-Sept-2008


Reference Load Cell Name

Syntax: ReferenceLoadCellName = string
Description: Name assigned to reference load cell used in FWD calibration.
Example: ReferenceLoadCellName = CLRP001


Reference Load Cell Calibration Date

Syntax: ReferenceLoadCellCalibrationDate = date
Description: Date of last calibration of reference load cell used in FWD calibration.
Example: ReferenceLoadCellCalibrationDate = 04-August-2004


Reference Load Cell Excitation Volts

Syntax: ReferenceLoadCellExcitationVolts = number
Description: Excitation value in volts for reference load cell used in FWD calibration.
Example: ReferenceLoadCellExcitationVolts = 10.000


Reference Load Cell Signal Conditioner Gain

Syntax: ReferenceLoadCellSignalConditionerGain = string
Description: Gain setting on signal conditioner used with reference load cell for FWD calibration.
Example: ReferenceLoadCellGain = 5.3 X 100
Note: The first number is the setting on the knob of the signal conditioner. It is    followed by the gain multiplier (pushbutton).


Reference Load Cell Unbalanced Zero

Syntax: ReferenceLoadCellUnbalancedZero = number
Description: The reading in volts with the load cell in an unbalanced condition.
Example: ReferenceLoadCellUnbalancedZero = 0.283
Note: By comparing this value to the daily value, the unbalanced zero reading is used to ensure the load cell is undamaged and working properly.


Reference Load Cell +B Voltage

Syntax: ReferenceLoadCell+BVoltage = number
Description: The reading in volts with the load cell balanced first when a shunt resistance is used to produce a positive voltage on the balancing circuit.
Example: ReferenceLoadCell+BVoltage = 1.772
Note: By comparing this value to the daily value, the +B and -B readings are used to ensure the signal conditioner gain setting is correct. A load cell with a very large gain may need to use the +A and -A shunts on the signal conditioner. In these   cases, the field names will have an A instead of a B in the field names.


Reference Load Cell -B Voltage

Syntax: ReferenceLoadCell-BVoltage = number
Description: The reading in volts with the load cell balanced first when a shunt resistance is used to produce a negative voltage on the balancing circuit.
Example: ReferenceLoadCell-BVoltage = -1.772
Note: By comparing this value to the daily value, the +B and -B readings are used to ensure the signal conditioner gain setting is correct. A load cell with a very large gain may need to use the +A and -A shunts on the signal conditioner. In these   cases, the field names will have an A instead of a B in the field names.


Reference Load Cell Calibration Units

Syntax: ReferenceLoadCellCalibrationUnits = string
Description: The units used in the calibration of the reference load cell (kiloNewton or pound-force).
Example: ReferenceLoadCellCalibrationUnits = pound-force


Reference Load Cell Calibration Coefficients

Syntax: ReferenceLoadCellCalibrationCoefficients = number(s)
Description: Polynomial coefficients used to convert volts into load in units listed under ReferenceLoadCellCalibrationUnits.
Example: ReferenceLoadCellCalibrationCoefficients = -98.2421e-01, 27.1714e-05,   61.1421e-09, 00.0000e+00, 00.0000e+00


Reference Load Cell Trigger Level

Syntax: ReferenceLoadCellTriggerLevel = number
Description: The load level in ReferenceLoadCellCalibrationUnits that is used to start auto-triggering and collection of data during FWD calibration.
Example: ReferenceLoadCellTriggerLevel = 1,000


Reference Load Cell Daily Unbalanced Zero

Syntax: ReferenceLoadCellDailyUnbalancedZero = number
Description: The daily reading in volts with the load cell in an unbalanced condition taken as part of the prerequisites of calibration.
Example: ReferenceLoadCellDailyUnbalancedZero = 0.283
Note: The unbalanced zero reading is used to ensure the load cell is undamaged and working properly.


Reference Load Cell Daily +B Voltage

Syntax: ReferenceLoadCellDailyPBVoltage = number
Description: The daily +B voltage reading taken as part of the prerequisites of calibration. Together with the -B reading, these data are used to account for variations in the setting of the gain by the FWD calibration center operator.
Example: ReferenceLoadCellDailyPBVoltage = 1.773


Reference Load Cell Daily -B Voltage

Syntax: ReferenceLoadCellDailyMBVoltage = number
Description: The daily -B voltage reading taken as part of the prerequisites of calibration. Together with the +B reading, these data are used to account for variations in the setting of the gain by the FWD calibration center operator.
Example: ReferenceLoadCellDailyMBVoltage = -1.773


Accelerometer Model Number

Syntax: AccelerometerModelNumber = string
Description: Manufacturer’s model number of accelerometer used in FWD deflection sensor calibration.
Example: AccelerometerModelNumber = 2220-005


Accelerometer Serial Number

Syntax: AccelerometerSerialNumber = string
Description: Manufacturer’s serial number of accelerometer used in FWD deflection sensor calibration.
Example: AccelerometerSerialNumber = 278


Accelerometer Reference Calibration Date

Syntax: AccelReferenceCalibrationDate = date
Description: Date of calibration of reference accelerometer provided by manufacturer.
Example: AccelReferenceCalibrationDate = 07-Sep-2004


Accelerometer Reference +1G DC

Syntax: AccelRef+1GDC = number
Description: Reading of accelerometer in a +1G field (volts) provided by manufacturer.
Example: AccelRef+1GDC = 0.825


Accelerometer Reference -1G DC

Syntax: AccelRef-1GDC = number
Description: Reading of accelerometer in a -1G field (volts) provided by manufacturer.
Example: AccelerometerRef-1GDC = -0.777


Accelerometer Reference Calibration Coefficients

Syntax: AccelRefCalibrationCoefficients = number(s)
Description: Polynomial coefficients to convert output in volts into acceleration in g provided by manufacturer where the first coefficient listed is co.
Example: AccelRefCalibrationCoefficients = -4.52e-02, 1.241e + 00, 1.048e-03, -1.369e-04
Notes: The form of the equation is acceleration (g) = co + ∑ (ci volts).


Accelerometer Daily Calibration Date

Syntax: AccelDailyCalibrationDate = date
Description: Date of the last daily flip calibration in dd-mmm-yyyy format.
Example: AccelDailyCalibrationDate = 03-Aug-2005


Accelerometer Daily Calibration Time

Syntax: AccelDailyCalibrationTime = time
Description: The time of the last daily flip calibration of the accelerometer in hour:minute
24-h clock format.
Example: AccelDailyCalibrationTime = 16:17


Accelerometer Daily Calibration Temperature Unit

Syntax: AccelDailyCalibrationTemperatureUnit = string
Description: Units of temperature used when performing the last daily flip calibration of the accelerometer (Fahrenheit or Celsius).
Example: AccelDailyCalibrationTemperatureUnit = Fahrenheit


Accelerometer Daily Calibration Temp

Syntax: AccelDailyCalibrationTemp = number
Description: Temperature recorded during the last daily flip calibration of the accelerometer in units of AccelDailyCalibrationTemperatureUnit.
Example: AccelDailyCalibrationTemp = 67.5


Accelerometer Excitation Volts

Syntax: AccelExcitationVolts = number
Description: Excitation voltage for the reference accelerometer.
Example: AccelExcitationVolts = 10


Accelerometer Signal Conditioner Gain

Syntax: AccelSignalConditionerGain = string
Description: Gain setting on signal conditioner used with for the reference accelerometer.
Example: AccelSignalConditionerGain = 2.0 X 1
Note: The first number is the setting on the knob of the signal conditioner. It is followed by the gain multiplier (pushbutton).


Accelerometer Daily Slope Factor

Syntax: AccelDailySlopeFactor = number
Description: Calculated relative difference in voltage between the reference calibration and the last daily flip calibrations.
Example: AccelDailySlopeFactor = -0.50486
Note: This value is multiplied by the output voltage to generate a relative voltage that can be used directly with the calibration factors from the accelerometer certificate (AccelerometerRefCalibrationCoefficients).


Accelerometer Historical Slope Factor Dates

Syntax: AccelHistoricalSlopeFactor = date, date, date, date
Description: Dates of the four accelerometer historical slope factors in dd-mmm-yyyy format.
Example: AccelHistoricalSlopeFactorDates = 12-Jan-2009, 02-Feb-2009, 27-Feb-2009, 18-Mar-2009


Accelerometer Historical Slope Factors

Syntax: AccelHistoricalSlopeFactor = number, number, number, number
Description: Historical listing of the previous four accelerometer slope factors.
Example: AccelHistoricalSlopeFactor = -0 49856, -0 49857, -0 49853, -0 49850
Note: These values are compared to the accelerometer daily slope factor during the FWD calibration to ensure the device is working properly.


Accelerometer Daily Calibration +1G Voltage

Syntax: AccelDailyCalibration+1GVoltage = number
Description: Recorded voltage in a +1-G field during the last flip calibration of the accelerometer.
Example: AccelDailyCalibration+1GVoltage = 1.7598


Accelerometer Daily Calibration -1G Voltage

Syntax: AccelDailyCalibration-1GVoltage = number
Description: Recorded voltage in a -1-G field during the last flip calibration of the accelerometer.
Example: AccelDailyCalibration-1GVoltage = -1.7598


Accelerometer Daily Calibration +1G Flip Voltage

Syntax: AccelDailyCalibration+1GFlipVoltage = number
Description: Recorded voltage in a +1-G field after the -1 g reading during the last flip calibration of the accelerometer.
Example: AccelDailyCalibration+1GFlipVoltage = 1.7698
Note: The daily calibration readings are used to confirm that the hysteresis of the accelerometer is not significant and will not adversely affect the FWD calibration.


Accelerometer Trigger Level

Syntax: AccelTriggerLevel = number
Description: The acceleration level in g units that is used to start auto-triggering and collection of data during FWD calibration.
Example: AccelTriggerLevel = 0.50


SPECIAL FORMAT FOR FWD CALIBRATION DATA EXCHANGE FILES

The information in this section will assist FWD manufacturers to adapt their FWD operating systems (field programs) to be more compatible with the FWD annual and monthly calibration processes. This section defines the format for a minimum subset of the many data items listed in the previous sections that is needed to facilitate calibration.

Electronic methods are used to transfer data between the FWD computer and the calibration computer. Some of this information is required just for record-keeping purposes, while other data items are used in the calibration calculations. Electronic data transfer helps reduce transcription errors and expedite FWD calibration.

At the beginning of a calibration, the FWD computer needs to provide some information about the load cell, deflection sensor serial numbers, the current gain factors, the FWD operator’s name, etc. The FWD operating program (field program) should be able to produce a file named FWDCalibrationInput dd-mmm-yyyy.DDX (where dd is the date, mmm is the month abbreviation, and yyyy is the year (e.g., 12-Nov-2009)). The contents of this file are defined below.

After an annual or monthly calibration is complete, the FWD operating program needs to be able to locate and read the results from a file named FWDCalibrationOutputdd-mmm-yyyy.DDX. The results should then be used to update the calibration data in the FWD computer.

Input Data Requirements for WinFWDCal

The following is an example of the contents of FWDCalibrationInput dd-mmm-yyyy.DDX. Only the data sections and data items are listed here. A complete description of each item is provided in the previous sections.

[Pavement Deflection Data Exchange File]
PDDXVersionNumber = 2.0
DelimiterSymbol = ,
DecimalSymbol = .

[Operations Information]
FileName =D:\WINFWD\Temp\FWDCalibrationInput 20-Feb-2009.ddx
EndDate = 02-20-2009
EndTime = 15:43
OperatorName = Daniel Atkins

[Units]
LoadUnits = pound
DeflectionUnits = mil

[Device Information]
DeviceDesignationName = Dynatest® FWD
DeviceModelNumber = 8001
DeviceSerialNumber = 8001-001
LoadCellSerialNumber = 0331
SensorSerialNumbers = 3170, 3162, 3163, 3164, 3165, 3166, 3167, 3168, 3169

[Device Configuration]
NumberOfDeflectionSensors = 9

[Device Calibration]
LoadCellAnnualCalibrationDate = 20-Feb-2008
LoadCellAnnualCalibrationGain = 1.0006
SensorAnnualCalibrationDate = 20-Feb-2008
SensorCalibrationGains = 1.001, 0.999, 1.001, 0.999, 0.999, 0.998, 1, 0.996, 0.999

Output Data from WinFWDCal

The following is an example of the contents of FWDCalibrationOutput dd-mmm-yyyy.DDX. Only the data sections and data items are listed. A complete description of each item is provided in the previous sections.

[Pavement Deflection Data Exchange File]
PDDXVersionNumber = 1.0
DelimiterSymbol = ,
DecimalSymbol = .

[Operations Information]
FileName = C:\WinFWDCal\InterimDropData\FWDCalibrationOutput 21-Feb-2009.ddx
EndDate = 21-Feb-2009
EndTime = 15:43
OperatorName = Daniel Atkins

[Device Information]
DeviceDesignationName = Dynatest® FWD
DeviceModelNumber = 8001
DeviceSerialNumber = 8001-001
LoadCellSerialNumber = 0331
SensorSerialNumbers = 3170, 3162, 3163, 3164, 3165, 3166, 3167, 3168, 3169

[Device Configuration]
NumberOfDeflectionSensors = 9

[Device Calibration]
LoadCellAnnualCalibrationDate = 21-Feb-2009
LoadCellAnnualCalibrationGain = 1.0005
SensorAnnualCalibrationDate = 21-Feb-2009
SensorCalibrationGains = 1.002, 1.002, 1.003, 1.000, 1.000, 0.999, 1.002, 0.997, 1.001

[FWD Calibration Center Information]
CalibrationCenter = Cornell Local Roads
CalCenterIDCode = 21
CalibrationCenterOperator = David Orr
CalibrationCenterOperatorCertificationDate = 18-Nov-2008
WinFWDCalVersionNumber = Version 1.4.18  22 December 2008
TypeOfCalibration = Annual


The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
FHWA
United States Department of Transportation - Federal Highway Administration