GPS is integrated with some models of variometer. An analog flight instrument that uses NODE+CLIMA as a variometer and altimeter. This was done by an adjustable air core transformer called a variometer (variocoupler). It is usual for gliders to be equipped with more than one type of variometer. Before the invention of the variometer, sailplane pilots found it very hard to soar. A type of continuously variable air core inductor is the "variometer". The minimal instrumentation required is an airspeed indicator and a variometer. A variometer is a very sensitive vertical speed indicator. Litz wire is used for the helix and variometer in both helix houses. The pancake coil variometer was another common construction used in both 1920s receivers and transmitters. But the variometer became key as pilots began making longer flights. A compensated variometer uses both speed and altitude to indicate the change in total energy. A variometer can be used to measure the rate of ascent of an aircraft. A variometer is a type of continuously variable air-core RF inductor with two windings.