In general clasification of instruments in power plant are divided as mechanical instruments which measures parameter like- pressure,flow,level,speed,temp,viscosity,humidity,moisture etc and electrical instruments which measures parameters like- voltage,current,power,energy etc.
classicifacion are also based upon controlling,recording,indicating, & integrating purposes.
1.Temp Measurement - Thermocouples (J,K,R,S,E etc Types) , RTD (pt100,pt1000,jpt500 etc), Liquid filled thermometer,Gas filled bulb & tube thermometer,Vap pressure thermometer, Pyrometer (optical,radiation).
2.Pressure Measurement - C-type bourdon pressure gauge(spiral,helical,twisted),Bellows, diaphragm gauges, vaccume gauges,manometer,draft gauges etc.
3.Flow Measurement - steam flow meter(flow nozzles,pitot tube etc), water flow meter & air flow meter(orifice,ventury,rotameter,hot wire annemometer), atomised steam meter.
4.Fuel Measurement - coal measurement(belt speed with load/min-load cell & tachometer), Gas meter(gas meter,positive displacement type disk-nutating),Oil Meter (rotameter,nutating disk,etc).
5.Level Measurement- boiler drum(hydra step,bubbler methode-clode vessel etc),bunker level & Ash(RF Type etc), hotwell,condenser,LP/HP Heater,Deareatoretc(Capacitive,hydrostatic,sight glass etc).
6. Speed Measurement - Turbine speed(stroboscope),motor speed,belt speed-tachometer,magnetic pick-ups etc.
7. Gas Analysis- CO+H2O,SOX-NOX,O2,CO2,calorific value of fuels measurement.

1.Current Measurement- Ammeter (generator load,feeder circuits,aux power,field circuit etc).
2.Voltage Measurement -Voltmeter(genarating & transmitting voltage,feeding voltage,motors voltages,etc).
3.Energy Measurement - Wattmeter (Power  generate,feeder powers).
4.Other Meters - Power factor,synchroscope,frequency,reactive power meter etc.