Series 3000 The measurement of Stress in underground workings is very important but difficult to achieve. HMA Geotechnical offers two types of Rock Stress Monitoring systems for borehole application. The first is a hydraulic type stressmeter which is similar in principle to an Earth Pressure Cell. This can be read using a bourdon tube pressure gauge or an electronic pressure sensor. The second type is a Vibrating Wire Stressmeter which works on a proving ring principle and is extremely sensitive. Both are installed in specially drilled boreholes and both can be read remotely.