Borgelt B400 AV variometer system                       16 Dec 2008

 Modern technology replacement for mechanical variometers with enhancements.

New for 2009!

Certain dealers or the factory can upgrade your B400 to latest software for a small charge. This incorporates a couple of minor bug fixes (most likely not noticeable), sets audio frequencies to latest standard and incorporates the (optional) silent zone from 1 to 4 knots sink when in “full range” audio mode. The last feature means that the audio is quiet in normal inter - thermal cruise but warns of excess sink or impending lift.

Contact the factory or your dealer.

Download B400 manual as PDF file: B400man.pdf


The system components are:


B400 AV (Variometer with Audio and Averager) Designed to replace mechanical variometers with modern technology with more useful features.

Built in audio, averager and unique to Borgelt Instruments, climb optimiser - green LED lights when vario is above 20 second running average reading – that is, average is getting better. You can select an audio change at this point also.

plus optional


Digital averager displays for B400 AV           DAD -S  and DAD -L




B400 AV


The B400 AV is designed to replace the well known B40 variometer and like the B40 is aimed at replacing the old technology mechanical variometers in the instrument panel of cross country and competition sailplanes as well as providing a good variometer with useful extra features (audio and averager)  for club and training sailplanes.


The B400 AV is available in both 57mm and 80mm sizes for easy installation in existing instrument holes and is only 85mm deep behind the panel including connectors (20mm shorter than the B40).


A standby power pack of 4  x AA alkaline batteries will provide at least 7-8 hours of operation in the event of main power systems failure.


A remote press button circuit or button in lower left enables the pilot to select the 20 second running average rate of climb at any time. The audio continues to function as a variometer during this time.


Alternatively one of two small full time digital averager displays may be driven by the  B400 AV. The advantage of the separate display is that it may be mounted in or very close to the instrument panel  glareshield, close to the pilot’s line of sight. One display is 38 x 14mm with 6.3 mm high digits (DAD-S) , the other is 50 x 21 mm with 12.5mm high digits(DAD-L). The displays are supplied with 0.5 m cables with plugs which plug in to matching sockets on the rear of the B400 AV.


The B400 AV uses surface mount technology in the electronics and the variometer display is by a small stepper motor driven pointer plus two high brightness LEDs. This provides the display with far better resolution and contrast than the LCD type pointers under all the changing lighting conditions typical in a circling sailplane. The display resolution is around 1/40 of a knot. This means a far smoother indication and much faster recognition of which way the pointer is moving particularly if the lift is weak. This is nearly 20 times the resolution of typical LCD pointers.


Audio is full range or “Up” only and there are two styles - “B40 Classic mode” with solid tone in sink (when full range selected) and 50:50 chopped tone in lift and a “competition mode” as follows:  At -10 knots (-5 m/s) the audio begins with clicks which become closer together as the sink decreases and then become a rising tone with the tone being chopped in lift. When the lift is above the running twenty second average the tone is chopped 50:50, when the lift is below the running average the tone is 70 on:30 off. Style selection is by a small switch accessible through a small hole in the rear cover of the instrument.


Volume control is by a centre off toggle switch in the upper right mounting screw position.(B400).


The instrument is supplied with an external speaker with case and mount. This avoids problems with the speaker magnetic field causing compass errors as the speaker can be remotely mounted which also helps audibility.


Total energy compensation is by TE probe making for easy installation and setup. Excellent TE probes are available from Borgelt Instruments.