tachometers, speed meters, accelerometers, pressure meters, photometers, luminoflux meters, illuminometers, refractometers, hygrometers, calorimeters, flowmeters, level gauges, level sensors, densimeters, concentration meters, gravimeters, viscosimeters, vibration gauges, dynamometers, metal or resin ships logs recorders, gauge comparators, interferometers, angle dividing apparatus, calibration checking apparatus, clinometers, angle gauges, pressure automatic control apparatus, vacuum automatic control apparatus, fluid flow automatic control apparatus, liquid level automatic control apparatus, fluid composition automatic control apparatus, automatic combustion control apparatus; program-controlling apparatus, namely electronic computer-controlled sequencers enabling sequence control by computer program, program-controlling instruments used to measure voltage current flow and electrical resistance, hydrophones, applied ultra-sonic echo sounders, applied ultra-sonic flaw detectors, magnetic object detectors, electronic computers, thermometers, planimeters, gas meters, water meters, level indicators, remote control and telemetering apparatus, distance measuring apparatus used to measure a moved distance or position of a crane or distance between two buildings, metal or resin capacitors, detectors used to detect the rotating rate or rotation angle of a motor, internal pressure and temperature of boilers, and the position and displacement of pistons, electrical circuit testing apparatus, oscillographs, recorders used to record variation of voltage and current on a recording paper or a magnetic tape