Abstract: A system for monitoring a machine (10) comprises a number of strategically placed sensing devices (11, 12, 13, 14) which are arranged to detect particular physical characteristics, such as vibration, thermal energy etc. Output signals from the sensing devices are delivered to a processor (15) which combines them to produce control signals indicative of the condition of a particular part or parts of the machine. In this way, the health of the machine can be continously monitored.

Abstract: A touch probe comprises a stylus-supporting member kinematically supported with respect to a housing at six points of contact between the stylus-supporting member and the housing. At each of these points of contact a conducting surface on the stylus-supporting member abuts a conducting surface on the housing. Each of the contacts are included in an electrical circuit. The conducting material of each of the conducting surfaces comprises a material having a resistivity of less than 8 .mu..OMEGA.cm and a melting voltage of at least 0.7 volts. A material having these properties is less susceptible to physical degradation than prior art materials used in such a probe. In a preferred embodiment the conducting material of each of the conducting surfaces is made of pure tungsten.