The 4239 Stacked Photoelectric Density Tool Sub uses two focused density detectors to compute borehole compensated density real time while logging. It also measures the amplitude of the returning gamma pulses using a photoelectric reader in order to determine lithology directly. It can distinguish between sandstone, limestone, dolomite, shale, and other rocks in the form of an additional logging curve. It also records caliper readings. It must be run with the 4000 Stack Gamma Ray Tool Sub, which provides the needed telemetry, and is compatible with the 4175 Stack Neutron Tool Sub.

FEATURES
Properties Measured
1. Caliper: Motorized, uphole actuated 33.02 cm (13 in.) Offset (measured from top of Gamma Ray Tool Sub): 589.79 cm (232.2 in.)
2. Far Density: 2.2 x 10.16 cm (0.875 x 4.0 in.) 35.8 cm (14.1 in.)  spacing Offset: 630.43 cm
3. Compensated Density: Cdl (compensated density log)  offset: 630.43 cm
4. Compensation: Comp (compensation) offset: 630.43 cm
5. Near Density: 2.2 x 3.2 cm (0.875 x1.25 in.) 20 cm (7.9 in.) spacing Offset: 638.25 cm
6. Photoelectric: 2.2 x 3.2 cm (0.875 x1.25 in.) 20 cm (7.9 in.) spacing Offset: 638.25 c
7. Radioactive Source: 200–300 mCi Cesium 137 bullplug Offset: 658.62 cm

Length: 348.13 cm (137.06 in.)
Temperature: 850C (185 F)
Diameter: 63.5 mm (2.5 in.)
Pressure: 175 kg/cm2 (2500 psi)
Weight: 58 kg (128 lb.)
Logging Speed: 9 m/min. (30 ft./min).