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Thin Layer Density Gauge

SKU: Model 4640 B Categories: , Tag:

Model 4640-B features patented technology to measure the density of thin asphalt and concrete layers from 2.5 to 10 cm thick (1 to 4 inches) without influence from underlying material. The 4640-B is specified by many state DOTs, government agencies and contractors as the best test method for determining the density of bituminous overlays.

Eliminates the need for nomographs and manual corrections: Variations in the density or composition of the base material do not affect the test results. No field calculations or charts are needed.

Operator selected depth of measurement: Enter the thickness of the overlay into the gauge memory and then accurately measure the overlay density (compaction) without influence from the underlying material.

Data storage is computer compatible: Store up to 750 readings by location and project number. Transfer stored readings to a printer or computer via RS232 interface. Additional site information can also be stored with each test.

The 4640-B meets or exceeds all applicable ASTM Standards.

The 4640-B calibration process is unique. Your test results will improve and job penalties can be eliminated. For special materials, up to 11 field calibrations can be performed and stored.

User friendly:
The operator will find the 4640-B very easy to use. It is a menu driven gauge, prompting the operator through the test procedure.


Technical specifications are subject to change without notice.

Mechanical Specifications

  • Case: Colored polycarbonate top shell withaluminum cast base
  • Operating Temp:
  • Ambient: -10 to 70ºC (14 to 158ºF)
  • Surface: 175ºC (350ºF)
    • Storage Temperature: -55 to 85ºC (-70 to 185ºF)
    • Gauge Size (excluding handles): 472 x 231 x 158 mm (18.6 x 9.1 x 6.2 inches)
    • Gauge Height (including handles): 240 mm (9.5 inches)
    • Weight: 13.5 kg (29.7 pounds)
    • Shipping Weight: 40.8 kg (90 pounds) w/transport case

    Radiological Specifications

    • Gamma Source: 8 ±1mCi Cesium – 137
    • Source Encapsulation: Stainless Steel
    • Shielding: Tungsten and lead
    • Surface: Dose Rates 5 mrem/hour max. top and sides of gauge, 15 mrem/hour
    • max. bottom of gauge, gamma in shield position

    Calibration Specifications

    • Accuracy of Density Standards: ±0.3%
    • Calibration Range: 1600-2700 kg/m3 / 100-170 pcf density

    Field Data Conversion

    4640-B contains a microprocessor providing direct reading in engineering units in pcf, kg/m 3 or g/cm3; no calculation is required.

    Electrical Specifications

    • Stored Energy: 30 watt hours
    • Battery Recharge Time: 14-16 hours (automatic shutoff)
    • Battery Recharge: 110/220 V, 50-60 Hz or 12-14 VDC
    • Power Consumption (average): 0.16 watt/hours
    • Readout (LCD) Liquid Crystal Display – 4 x 6 alpha numeric
    • Battery packs are fully protected against overcharge and overdischarge.
      Provided with RS232 interface. Capable of operation with D size batteries for emergency use.

    Special Functions:

    Automatic standard count comparison and storage. Determination of count time for selected precision. Field offsets of density. Field calibration for special asphalts. Calculator mode with storage. Self-test and service programs: Display, Keypad and Ram Test; GM Tube Test; Statistical Stability and Drift Test.


    Accessories are not included in the price of main device (unless stated otherwise) and may be purchased separately if required.

    Standard Accessories:

    • Supplied with the Model 4640-B: air gap fixture, 1” magnesium block,
      AC battery charger, DC charger cord, transport case

    Optional Accessories:

    • PN 021140 Radiation Sign Kit, PN 102866 Leak Test Kit