- abampere
- absence interaction
- absorption dynamometer
- accumulated error
- accumulating counter
- abcoulomb
- absorption hygrometer
- AC-coupled
- absiemens
- accidental signal
- accurate map
- actual current
- actuating system
- acoustical thermometer
- actual indication
- adaptive control
- additional winding
- adjustable stop
- adjusting element
- adaptive sampling
- adjustable potentiometer
- adjustable screen
- adjustable screw
- adjustable strap
- advanced component
- aerometric method
- aerophotogrammetry
- air thermometer
- air leak
- airflow meter
- air-gauge
- alarm thermometer
- amplitude squeezing
- aneroid
- arrows
- astrogeodetic network
- arbitrary grid
- asynchronous control
- aspiration psychrometer
- atomic heat
- attenuated
- attenuation
- auditor
- autoadaptivity
- automata theory
- automatic controller
- automechanism
- azimuth compass
- back arrow
- back indication
- backlash-free
- autostability
- balance indicator
- balance point
- ball gauge
- base mark
- basic noise
- basic speed
- beam support
- bearing compass
- bearing instrument
- Beckman thermometer
- base network
- basic instrument
- batching counter
- bathymetry
- beam
- bearings
- bell flowmeter
- bellows gage
- bellows gauge
- belt balance
- bevel protractor
- bevel square
- bias error
- bimetal thermometer
- binary counter
- bimetallic thermometer
- binnacle cover
- block system
- bolometric instrument
- bomb calorimeter
- bone in
- boolean term
- bore gauge
- Bourdon gage
- bourdon gauge
- box compass
- bob
- bolometer
- bottle counter
- branch transmittance
- buoyancy probe
- break frequency
- bridge balance
- brightness meter
- breakpoint switch
- buzz
- calibration limit
- busy line