- overpressure gauge
- parallactic compensation
- parallax-free
- parallel structure
- Parr calorimeter
- peck
- pelorus
- pendular dynamometer
- perforation
- permeability logging
- perturbation signal
- personal error
- phase bridge
- phase crossover
- phase margin
- photoelectric control
- photogrammetric network
- piche evaporimeter
- pilot hole
- pioneer well
- pipe flowmeter
- phlebomanometer
- photoelectric sorter
- pica
- piezo
- pilot well
- picnometer
- pitometer
- pitot tube
- planner
- plant instrument
- physical realizability
- piezometer tube
- pipelined architecture
- pipet
- plant decomposition
- playback accuracy
- polar plot
- pole
- pole tester
- pole-positioning
- positioning force
- positive feedback
- porosity log
- potentiometric controller
- potentiometric meter
- pound
- potentiometer method
- power cylinder
- power mains
- power meter
- power recorder
- precipitation heat
- precision balance
- precision gage
- precision gauge
- precision manometer
- precondition
- preece
- preselection switch
- preset counter
- presetting gage
- pressure transducer
- pressure viscometer
- presetting gauge
- pressure indicator
- process management
- processing
- pressure bellows
- process value
- program control
- programmable
- programming panel
- programmable controller
- projector compass
- prompting
- proportional degree
- proportional counter
- proportional element
- proportioning device
- proximity sensor
- proving hole
- pycnometer
- quality assessment
- radio-meter
- radioactive log
- radiometric source
- rate
- rated accuracy
- ratio measurement
- reaction
- realizability
- ramp encoder
- ramp response
- rangefinder window
- rate action
- rate control
- rate fixer
- reaction value
- Reaumur thermometer