4640-B Surface Thin Layer Density Gauge

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Product Brochure

Recognizing the need for an improved method of measuring the density of thin layer asphalt overlays, Troxler developed the first true thin layer density gauge, the 4640-B Surface Thin Layer Density Gauge.

Designed to measure the density of thin asphalt and concrete layers from 2.5 to 10 cm (1 – 4 inches), the Troxler Model 4640-B Thin Layer Density Gauge accurately measures the overlay density without influence from underlying material. No nomographs or manual corrections are required in order to compute the true density of the overlay. With onsite results available in as little as one minute, the Model 4640-B can provide the user with test results when they are needed, not hours after compaction has been completed.

Special Functions

  • Automatic standard count comparison and storage
  • Data storage of 750 records for later viewing, printing, and/or downloading
  • Determination of the count time for selected precision
  • Field offsets of density and a special calibration function
  • Calculator mode
  • Diagnostics and self-test modes
  • Simple data transfer to a portable device using the free Troxler App

The Troxler Model 4640-B Thin Layer Density Gauge complies with ASTM D2950 and AASHTO T 355.


Gauge Precision ±1 std. deviation at 2240 kg/m3 [140 pcf])
Time (minutes)
2.5 cm (1″)
5.0 cm (2″)
6.3 cm (2.5″)
2.5 cm (1″)
5.0 cm (2″)
6.3 cm (2.5″)
Depth of Measurement 25-100 mm (1-4 inches)
Accuracy of Density Standards ±0.3%
Calibration Range 100-170 pcf (1600-2700 kg/m3) Density
Gamma Source 8 ±1 mCi Cesium-137
Troxler Drawing Number TEL A-102112
Source Housing Stainless Steel Encapsulation (single or double)
Shielding Tungsten and lead
Surface Dose Rates 5 mrem/hr max. top and sides of gauge
15 mrem/hr max. bottom of gauge, gamma in shield position
Shipping Case DOT 7A, Type A, Yellow II Label, 0.2 Transport Index
Sealed source approved for domestic and international shipment CS-127, Special Form Certificate
GB:SFC 140
Stored Energy 30 watt-hours
Battery Recharge Time 14-16 hours (automatic cutoff)
Charge Source 110/220 VAC, 50-60 Hz or 12-14 V DC
Power Consumption 0.1t6 watt-hours
Readout 4×16 alpha-numeric LCD
Case Colored polycarbonate top shell with aluminum cast base
Operating Temperature 32º to 122º F  (0º to 50º C)
Gauge size without handles 18.6 x 9.1 x 6.2 inches
(472 x 231 x 158 mm)
Gauge height with handles 9.5 inches (240 mm)
Storage Temperature 0º to 140º F  (-18º to +60º C)
Weight 29.7 lbs. (13.5 kg)
Shipping Weight 90 lbs. (40.8 kg) with case


  • The Model 4640-B provides you with these advantages:
    • True thin layer gauge – no nomograph calculations needed
    • No need to measure the density of base materials
    • Stores up to 750 test results
    • twelve month warranty