pFLEX - Portable Soiling/Cleanliness Handheld Reflectometer

The degree of soiling on mirrors (quantified e.g. by the cleanliness factor) is of high interest for concentrating solar systems (CSP, CPV). 

The new pFlex instrument of PSE AG was developed in collaboration with Fraunhofer ISE. It is easily handled and operated and offers precise measurements as well as simple data storage and transfer. The instrument is operated via an user interface on a mobile phone, further simplified by optional operating buttons on the instrument itself. The quick data acquisition is insensitive and robust against slight tilt or twist of the instrument, which highly facilitates handheld operation in a solar field when measuring tilted or even tracked mirrors. The pFlex has been specifically developed to be operated in the harsh environment of arid deserts and typical CSP/CPV sites. 

Technical specifications

Directional reflectance measured at wavelength of 631nm (optional 455, 533, 660)  
Incidence angle
Measurement field 10mm (signal averaged over measurement field)
   Absolute accuracy of reflectance measurement +/- 0.01
   Relative accuracy / repeatability +/- 0.005
   Standard deviation of repeatability 2.0‰
User interface Graphical user interface on a mobile phone
   Data storage Primary data evaluation and storage on a mobile phone
   Data format ASCII
   Data interface USB 2.0 Micro-B and Bluetooth between smartphone and device
Operation temperature range -15°C to + 60°C (limited by LiFePO4 power pack)
Power supply 11-15V DC
Battery operation time (Rechargeable LiFePO4 power pack) > 24h
Size: height / width / depth 215x135x59mm

Applications and advantages

  • Mobile/portable precision measurement of specular reflectance
  • Designed for measurement of flat and curved reflectors
  • Easy and robust handling during data acquisition
  • Simple data storage and data transfer
  • Optional output: Reflectance or cleanliness factor
  • Easy monitoring of the soiling of specularly reflecting surfaces
  • Daylight suppression for measurement under bright daylight and direct solar irradiance

Delivery includes

  • Reference mirror 
  • Mobile phone with installed operation software app 
  • Industrial quality transport case

Operation via Android App “Reflect UI”

A mobile phone / smartphone with pre-installed app is provided with the pFlex device. The measurement is operated with an interface provided by the app “Reflect UI”. Meta data and operation commands are given on the phone’s touchscreen. Furthermore the measurements are evaluated and displayed directly. The measured data can be stored on a built in MICRO SD memory card. The app has multiple features and operation modes, as shown on the screenshots below. The standard mode gives the results of the reflectance measurement. A list of the measurement results and the reflectance is displayed in the live-mode. The live-mode shows in real-time the reflectance of the sample. Settings can be changed at any time and are displayed in the live-mode and on the connection menu. The smartphone communicates with the device via Bluetooth. A user manual of the app is provided with the hardware.