The term "variometer" is most often used when the instrument is installed in a glider or sailplane. An "Inertial-lead" or "Instantaneous" VSI (IVSI) uses accelerometers to provide a quicker response to changes in vertical speed.

What is the use of variometer?

A variometer is used to measure the variation of the field components about baseline values, in a continuous and unattended way, at the required sampling rate, say 1/minute.

What is the purpose of vertical speed indicator?

A Vertical Speed Indicator (VSI), also known as a Rate of Climb and Descent Indicator (RCDI) is an instrument which indicates the rate of climb or descent of an aircraft.