SOLYS2 Sun Tracker

  • Fully automatic Sun Tracker
  • Integrated GPS receiver
  • Easy to install
  • BSRN level performance
  • No regular maintenance required  


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SOLYS2 Sun Tracker

SOLYS2 is the most widely used sun tracker around the world in solar energy and meteorological applications. It has Baseline Surface Radiation Network (BSRN) levels of performance and reliability. Installation and operation of the SOLYS2 is much easier than many other sun trackers on the market.

With the optional top mounting plate and shading assembly SOLYS2 can be configured as a complete solar monitoring station with up to three ventilated Kipp & Zonen radiometers. A large range of mounting kits is available for direct solar radiation instruments.

An advance over conventional sun trackers is the integrated GPS receiver to automatically configure location and time data upon installation. SOLYS2 does not require a computer and software for setup. Leveling is easily checked using the integrated bubble level on top.

The rugged and distinctive cast aluminum housing has an integrated tripod stand with leveling feet, azimuth adjustment and provision for tie-down bolts. A side plate with zenith adjustment and mountings for a Kipp & Zonen CHP1 pyrheliometer is included.

SOLYS2 does not suffer from internal clock drift because the time is regularly updated by the GPS receiver. If the tracker is correctly leveled and aligned, and mounted on a solid and stable support, it will continue to point accurately. An optional sun sensor is available for active tracking, to correct for motion in a support affected by changing environmental conditions.

SOLYS2 can operate from AC or 24 VDC power, both inputs are available as standard. The operating temperature range from - 20 °C to + 50 °C on DC power can be extended to -40 °C on AC power using the standard internal heater.

SOLYS2 brings to the sun tracker market distinctive design, innovative features, performance, quality and unprecedented ease of use – all at a surprisingly affordable price.

The design of the SOLYS2 sun tracker is based on open source software.

For instructions on the installation please watch this video and don't forget to read the manual too.

Sun Tracker Comparison

OTT HydroMet offers three different models under its trusted brand Kipp & Zonen. The RaZON+, the SOLYS2, and the SOLYS Gear Drive. Read how to choose the right sun tracker model for your purpose on the OTT HydroMet Blog.

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Pointing accuracy < 0.1° passive tracking / < 0.02° active tracking (with optional sun sensor)
Payload 20 Kg
Power supply 18 to 30 VDC and 100 to 240 VAC (50/60Hz)
Operating temperature range, DC -20 to +50 °C
Operating temperature range, AC -40 to +50 °C
Mounting base Tripod stand
Dimensions 50 x 34 x 38 cm / 23 kg ( tracker) 5 kg (tripod)
Communication interface Ethernet / Web interface
Transmission type Inverted tooth belts
Power consumption 21 W (reduces to 13 W at night) 100 W extra when heater is operating (AC only)


  • Why is the altitude limited to 2000 m?
    • The 2AP BD altitude specification (2000m) is limited by the CE and CSA (Canadian Standards Association) recommendation for main power board design. CSA recommends that AC boards have certain spacings between the board tracings for various elevation (pressures). As the pressure decreases there is more probability for arcing when the wires are close. Unfortunately there is not enough room internally, in the 2AP BD, to increase the size of this board (to make the spacings bigger).

      The best solution is to sell/quote a 2AP Gear Drive with 24VDC, as this would eliminate the altitude restrictions associated with high voltage AC.

      Is your question still unanswered? Contact Support
  • Is there a way to fix a tracker via remote PC?
    • You can try the following:
      If you send the command “CO”, the 2AP will cold start. This means ignore all present settings and start without using any previous (possibly wrong) settings.

      If you then start the sun tracker program, it will start up with the message “”recovering from cold start””

      Then longitude and latitude etc. will be recovered from the .ini file, the time and date of course cannot be stored and has to be entered again. If no further error message is given, the 2AP is most likely operational again.

      This could solve the problem, if not please contact us and we will discuss further options.

      Is your question still unanswered? Contact Support
  • Is compensation for pressure variations needed?
    • The air pressure that is required should be an average value for the site the instrument is operated. It does not need to be updated over time. The meaning of it is to correct for (a small) optical shift due to atmospheric pressure. A normal value depends of course on the heath of operation. A value of 1000 mBar is typical for sea level.

      Is your question still unanswered? Contact Support
  • Is there a compensation for temperature drift?
    • The controller board has a temperature compensated oscillator module for the microprocessor. While power is applied the firmware keeps accurate time and updates the real time clock (which is not very accurate) every 8 hours.

      We enter a room temperature correction, which compensates for initial calibration of the oscillator module. The oscillator module can drift up to ±11 ppm over the 0 °C to 70 °C temperature range. The module can also drift up to ±2 ppm in a year.

      The temperature drift is different for each oscillator so cannot be compensated for in firmware.

      Is your question still unanswered? Contact Support
  • What is the range of the temperature?
    • The temperature range for the 2AP tracker is:

      Standard temp range: 0 - 50 degrees Celsius
      With cold cover: -20 - 50 degrees Celsius
      With cold cover and heater -50 - 50 Degrees Celsius

      Normally the heater is built in, in the factory. However we can supply you with a kit plus instructions to do it yourself.

      Is your question still unanswered? Contact Support
  • What is the accuracy of the 2AP tracker in combination with a sun sensor?
    • The 2AP has the following errors:

      • Time
      • Setup (leveling)
      • Calculation (algorithm according to Michailsky error max. is 0.025 degree)
      • Mechanical (BD = 0.09 and GD =0.045 degree max.)

      The first 2 are user controlled and the last 2 are fixed.

      Assuming that the leveling is done optimal the only error remaining that can be corrected is time. If we assume that the clock is reset every 1,000,000 seconds (11.5 days) there will be an expected error of 5 seconds. If we assume that the sun rotates 360 degrees in 24 hour then RMS 0.72 * 5 seconds = an actual time error of 3.6 seconds. For a period of 11.5 days the total time error contribution is 0.015 degrees (the diameter of the solar disk is 0.25 degrees). Per year this would result in 0.5 degree.

      If this time correction and the check on leveling are done on a regular interval there is no need for a sun sensor. If however this interval can or will not made, the sun sensor will correct for both (leveling and time).

      The sun sensor is normally used for first checking the tilt error. Assuming that there is sunshine for at least 2 full days over the full day. This information is stored in an internal log file and used to correct (in combination with PC). Over this period the user has to correct time. (if more than 2 weeks). After this initial run and correction for tilt, the sun sensor is used for time correction. This means that optimal accuracy is maintained without user (time) correction. This means that the 2AP is within specs the whole year without intervention.

      Please note that the sensors used on the 2AP also need maintenance on a regular base (drying cartridge and dirt on domes).

      Better than giving an error in percentage we would like to show the benefit of not having to correct to clock. The 2AP error in degrees can be calculated as percentage of 360 degrees, but the error in sensor reading depends on the type of sensor.

      Is your question still unanswered? Contact Support
  • Why does the COM port of my Pentium not address the 2AP like my old 4.86?
    • The CMD and sun tracker software will work on COM1 or COM2 only, specified as the first parameter after the program name in the command line. Make sure the 2AP is connected to one of these two ports. Problems can also occur if another program has taken over the COM port and will not give it up. Also, some Compaq computers have non-standard COM ports, which the CMD and sun tracker programs cannot communicate through. The solution for this problem could be found in a simple add-on card with a standard extra serial port, if it can be set as COM 1 or 2.

      Is your question still unanswered? Contact Support
  • Can the tracker be connected to a PC at 30 m distance?
    • To connect the 2AP with a PC for communication, a 3-wire cable is used (or 2 wires plus shield) as described on page 5 of the manual.
      Advised is a shielded cable, where the shield can be the ground connection.

      • On the 2AP side the wires are connected to the communication board.
      • On the PC side a 9 or 25 pin Sub D connector is used for the serial port.

      This cable length can be 30 meter. We can supply this cable, but it can be bought "around the corner".

      The communication software is included with the 2AP.

      Is your question still unanswered? Contact Support
  • Does the 2AP work autonomously?
    • The 2AP works fully autonomously, after the setup. Setup is done in combination with a PC. (Entering Longitude, Latitude etc.) Indeed a data logger is needed to collect data from the sensors, but this logger has no (hardware) connection with the 2AP.

      Is your question still unanswered? Contact Support
  • What power supply is needed when heaters are used?
    • The power use of the 2AP itself is about 1.5 A to 2 Amps. (Internal fuse is 3 Amps slow)

      Part number for the 24V heater kit is: 12136346.
      This kit contains two 50 Watt heaters.
      So the current for these heaters is 4.2 A (at 24V), fuse is 5 A slow blow.

      If we add up the total power we have:
      5A (heaters) + 3.15 (2AP)= 8.15 A

      Normal conditions:
      4.2 A (heaters) + 1.25A (2AP) = 5.5 A normal

      Therefore a 5 Amp power supply will not survive very long.
      We recommend to take a power supply that can deliver the 8.15 A. (when heaters are used)

      Is your question still unanswered? Contact Support
  • How much power is needed for the 2AP?
    • The power use of the 2AP itself is about 1.5 A to 2 Amps. (internal fuse is 3 Amps slow)

      Is your question still unanswered? Contact Support
  • Is it possible to mount 4 pyreliometers plus an extra sun sensor?
    • Yes. Normally 4 of these side-mounted sensors is the maximum, however we are able to make an extension on one pyrheliometer mount for the extra sun-sensor.

      Is your question still unanswered? Contact Support


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