For those out there that are really enthusiastic about pushing your drone and air model to the limit, putting it to professional use, here are our best suggestions of sensors to further improve your fpv radio telemetry kit! Throughout this article, we will explore some of the remarkable characteristics of said sensors.

First, there is the FrSky Variometer Sensor Vario - High Precision. This device, when working in association with a telemetry-compatible Transmitter and Receiver, can indicate to the pilot the altitude and altitude change-rate of the object to which it is attached to. All this data can be recorded and used for a flight analysis later on.

And second, another indispensable sensor: FrSky ASS-70/ASS-100 Smart Port Air Speed Sensor. As the name already implies, this sensor can indicate your aircraft’s real-time speed. The ASS can not only provide the speed data but also warn the pilot of low airspeed, check your top speed, program your radio to automatically drop the landing gear at a preset airspeed, etc,  when it is properly set up to do so.

Variometer Sensor

The high-precision FrSky Variometer Sensor is quite a tiny device. Taking the space of a 31.1 mm x 18.3 mm x 6 mm rectangle (about 3.4 cubic cm) and weighing only 3.1g, it will fit wherever you wish to plant it. Size is certainly not a handicap! This high-precision version of the Variometer can measure altitudes from 700 m below sea level up to 10 km above it with 0.1 m of resolution!

This sensor calculates the altitude from the measured atmospheric pressure. Atmospheric pressure will get lower as you go up in altitude and this is the correlation that the sensor uses to estimate the altitude with such a high resolution. Moreover, the Variometer sensor outputs the Altitude Variation Rate via DA port.

The Variometer outputs both absolute altitude and relative altitude (do refer to its instruction manual to learn how to switch between the two options). The relative altitude will set your 0 m right where you start, displaying the change in altitude from there.

Not only does it present backward compatibility with existing sensor hubs and sensors, but it is also capable of connecting directly to the telemetry receivers without the sensor hub. This Variometer Sensor is also compatible with the new generation of Smart Port enabled sensors and FrSky’s X-series receivers with S.Port, as well as FrSky’s D-series receives with AD Port.

Furthermore, there is an additional and certainly special feature: with Smart Port enabled, this sensor can form a two-way full-duplex transmission, acting as a “bridge” of communication between an S.Port-enable telemetry sensor system and a Non-S.Port-enabled one.

You can buy one at and it will cost you less than $25! There you will also find a normal precision version of the sensor that is even cheaper than this one, with 1 m of resolution. Both will be perfect for your radio telemetry kit!


FrSky Variometer Sensor Vario - High Precision

AirSpeed Sensor

There are actually two versions of this airspeed sensor model. The SP-ASS-70 can accurately measure airspeed up to 167.7 mph (270 km\h), whereas the SP-ASS-100 measures up to 223.7 mph (360 km/h).




By following just a few simple steps (as explained and illustrated below), you can prepare the FrSky ASS-100 Air Speed Sensor to start gathering the airspeed data.

  1. Install the pitot tube as far away from any prop wash or any disturbed air as possible - preferably at a minimum of 13 mm past the wing’s leading edge or past any other obstructions;
  2. Run the silicone tubes/hoses, from the pitot tube’s outputs to the proper entry on the sensor;
  3. Position and attach the AirSpeed sensor circuit board in the fuselage of your aircraft, somewhere that can be reached by the hoses;
  4. Connect the sensor to the receiver, or another Smart Port sensor;


FrSky ASS-70/ASS-100 AirSpeed Sensor Installation Scheme

Just like the Variometer Sensor, this airspeed sensor was also designed to be used with FrSky Smart Port enabled systems and compatible receivers, such as the X8R, X6R, X4R from the X-series, which means that they can daisy chain with each other.

You can purchase both the ASS-100 and the ASS-70 S.Port AirSpeed Sensors at HorusRC online shop for $50 and $23.49, respectively.