ASTM D 1558
This is identical to above, except that the penetration pressure on the needle is conveyed through a hydraulic system to a hydraulic pressure gauge. This system permits a greater control over rate of penetration because of better visibility of load indication on the gauge.
Comprises hydraulic proctor needle system complete with a pressure gauge fixed at easily readable angle reading 0-70 kg x 2 kg. A set of needle points consisting one each 0.25, 0.5, 1.0, 1.5, 2.0, 3.5 and 6.0 sq. cm. and a wooden carrying case.