• ST-5 Sun Tracker
  • ST-5 Sun Tracker with SolarSIM-G
  • ST-5 Sun Tracker with shadow disc

direct irradiance measurement platform

ST-5 sun tracker

By employing the latest advances in tracker technology, the ST-5 makes direct and POA irradiance measurements refreshingly simple and affordable for research and industry alike.

Compatible sensors: SolarSIM-D2, SolarSIM-G, third-party pyrheliometers/pyranometers.
Technology: Dual/single-axis, SPA-based, automated sun tracker.
Highlights: State-of-the-art technology ensures the optimal combination of performance and price for all applications.

A dedicated direct irradiance measurement platform.

By employing the latest advances in tracker technology, the ST-5 achieves a breakthrough in the cost of accurate, reliable solar tracking.

The ST-5’s compact size and weight make transport, installation and maintenance refreshingly simple and affordable. With a payload limit of 5 kg, the ST-5 can be configured to hold up to 4 direct or global SolarSIMs, or an equivalent mass of non-Spectrafy instruments.

The ST-5’s automated control box employs a highly accurate and efficient solar positioning algorithm to determine the sun’s location, while the precision engineered hardware ensures pointing accuracy of ±0.1º. For custom uses, optional PC-based software allows manual control.

The on-board GPS automatically configures time and location upon start-up and eliminates internal clock drift, while the ST-5’s integrated leveling feet, azimuth adjustment and tie-down bolts enable swift and easy installation via the integrated bubble level.

Total control - if you want it.

Standard operation

Under standard operation, the ST-5 Sun Tracker requires no external comms connection to operate.

PC Connectivity (optional)

The ST-5 Sun Tracker can be connected to a PC to enable custom control of pointing algorithms and position.


Pointing accuracy ± 0.1 º
Payload 5 kg
Elevation range 0º to 125º
Azimuth range 0º to 360º
Over-rotation protection Physical limit stops
Tracking mode SPA based (open loop)
Heating Optional
Control Automated control box or RS-485 ASCII direct to PC


Weight 6 kg
Dimensions (W x D x H) 233 x 140 x 235 mm
Power supply and use 12 VDC, 34W in motion, 4W when idle, ~70 Whr/day
Operating temperature range -25°C to +55 °C (-40°C to +65 °C optional)
Humidity range 0 to 100% RH
Environmental protection IP66
Standard cable length 10 m

The go-to solution for a wide range of applications.

Solar R&D The most affordable and flexible direct irradiance measurement platform for R&D. The ST-5's software allows for unmatched flexibility in tracker control.
Meteorological networks Upgrade your network with the ST-5 to realise lower longterm maintenance costs.
Solar resource assessment - DNI The ST-5 makes on-site DNI measurements a feasible and affordable component of resource measurement campaigns - significantly reducing the expanded uncertainty of PV performance models.
Solar resource assessment - POAI The ST-5 can be deployed in elevation-only mode, mounted with the SolarSIM-GPV, in order to measure spectrally corrected, plane-of-array irradiance. Thereby providing the most accurate assessment of the solar resource for modern PV plants.
Solar power plant O&M Better monitor, understand and optimize your PV asset in real-time with on-site DNI measurements.
CSP & CPV The ST-5 represents a big step towards routine, affordable DNI measurements for CSP and CPV plants.
Custom applications The ST-5 Sun tracker can be controlled/programmed by the user to follow custom positioning algorithms.

Why would I choose the ST-5 over other solar trackers?

The ST-5's embrace of modern PTU technology makes it the most cost-effective, direct irradiance measurement platform on the market.

What sensors can I mount on the ST-5?

The ST-5 is sensor agnostic. It can be used to mount our SolarSIM sensors, or any third-party pyrheliometer or pyranometer. A range of mounting fixtures are available to support all major sensor manufacturers.

What measurements can I perform with the ST-5?

The ST-5 currently supports direct irradiance measurements - either direct normal or direct global. Contact us if you would like to use the ST-5 to measure diffuse irradiance or global horizontal irradiance.

Does Spectrafy sell complete measurement systems?

Yes, we can provide you with a complete turn-key system so you can hit the ground running.


MP-D2 Mounting Plate

We offer a range of standard, anodized aluminum mounting plates suitable for mounting the SolarSIM-D2 to various solar trackers. Also compatible wtih the SolarSIM-G, SolarSIM-GPV, SolarSIM-GUV and SolarSIM-3C. Custom options are also available.


The original SolarSIM, for measuring spectral and broadband DNI and atmospheric parameters.


Our spectral sensor for measuring spectral and broadband global irradiance.


Our spectral pyranometer for measuring GHI and PV spectral correction factors.
ST-5 Sun Tracker with Shadow Disc Assembly
The ST-5 Sun Tracker's shadow disc assembly can be used in conjunction with the SolarSIM-G to enable highly accurate measurements of diffuse horizontal spectral irradiance and DHI. The shadow disc assembly can also be used with third-party pyranometers to enable highly accurate measurements of DHI and meets the requirements for Class A DHI measurement for solar power plant applications.