Frequently Asked Questions

What type of LED's and colors can be tested?
Many types of LED can be tested ranging in colour from White, Blue through Green to Red and even Infra-Red. All shapes and size of LED can be tested including Bi-Colour, Tri-Colour, LED Displays and Bargraph Displays. The only requirement is to position the end of the optical fiber or the Optical Head near the illuminated LED. Any brightness level can be tested, from Backlit Indicators up to Automotive Headlights.
Can Flashing or Blinking LED's be tested?
Yes, Flashing and Blinking LED's can be tested. Please look up the user manual of the LED Analyser to get more information about this topic.
Can 7-Segment Display's be tested?
Yes, each segment can be treated as a single LED by positioning the fiber end in front of it. Even displayed numbers such as 0, 1 ..9 +,- can be verified and read back through the Analyser. This can be very useful in a closed loop system where the requirement is to verify a display reading.
Can Bi-Colour and Tri-Colour LED's be tested ?
Yes, each colour should be turned on individually and its RGB or HUE value read back.
Can Bargraph Displays be tested?
Yes, Bargraph Displays can be tested. If a fiber is placed over each segment of the Display then its colour and intensity can be measured.
Can all LED's be tested simultaneously?
Yes, the LED Analyser can measure up to 20 LED's simultaneously. The time needed to capture and read back the values is around 1 second.
What output formats are available from the unit?
The Analyser can output results through the USB or RS-232 Serial port or through a dedicated ICT Port. The RGB, HUE, Saturation, xy Chromaticity, Intensity, Dominant Wavelength and CCT (Correlated Color Temperature) values of each LED can be output.
How much time does it take to test 20 LED's?
The Standard Capture time is around 100ms to 700ms. The Test Time depends on the capture range selected for the test. It will take approximately 100ms to test 20 LEDs at the highest range and 700ms for the lowest range.
What is RGB?
RGB stands for Red Green Blue. Each colour is split into the three primary colours and these values are output from the Analyser.
What is HUE ?
HUE (HSI = HUE Saturation and Intensity). HUE is a value from 0 to 360 degrees and is another way of representing the RGB values as a single number. Pure Red is 0, Pure Green is 120 and Pure Blue is 240. Amber which is a combination of Red and Green with a small amount of Blue is around 15. Orange is around 30 and Bright Yellow is around 60.
How is the unit mounted in a Fixture ?
There are four mounting holes on the ICT unit which can be used to attach the Analyser to a Base Plate.
What options are available to connect the unit to a PC ?
The LED Analyser can be connected to the Serial or USB port of a PC. A Serial or USB cable is provided with the unit (it depends of the version).
How close to the LED should the fiber be mounted ?
3-5mm is usually best, but may be greater or smaller depending on the application.
What is the minimum bend radius for the fiber ?
The minimum bend radius recommended by the manufacturer is 15mm (0.6 Inches). Sharper bends can be tolerated but the loss will start to increase in the fiber.
How long can the fiber be in length ?
The fiber length can be extended if required. We currently have the length set to 0.6m or 20inches approximately. The only issue is the amount of loss you can tolerate in the fiber. The longer the fiber the greater the loss. For example, in a 30m (49 feet) length of this fiber there will be a 3dB (50%) loss. If the LED being tested is bright then higher losses can be tolerated and still be able to measure color. If Intensity is being measured then the fiber loss must be taken into account.
What are the power requirements ?
5V DC 200mA.
Why does a red LED which looks the same brightness as a green LED measure much higher intensity ?
The Human Eye is less sensitive to red light so a Red LED can be brighter than it looks! The absolute intensity scale reproduces the photopic response and avoids this effect.
What is the format of the serial protocol ?
The serial protocol used to communicate with the LED analyser is very simple. A Terminal can be used to demonstrate the communication with the LED Analyser.  Feasa provides their own ‘Feasa Terminal’ to communicate with the Analyser. The same commands can be used from any programming language.

The settings are as follows RS-232 57600 baud 8 Data bits, 1 Stop bit, No Parity, No Flow Control.
This is a communication example for the LED Analyser USB/ICT versions using the serial interface:
All commands are terminated with Carriage Return + Line Feed (CR + LF)

- Send CAPTURE + (CR+LF) to the Led Analyser to trigger data capture. The system responds with OK
- Send GETRGBIxx to retrieve RGB data for LED xx (01 = fiber 1, 02 = fiber 2 etc.).
Analyser responds with rrr ggg bbb iiiii where
rrr is RED value
ggg is GREEN value
bbb is BLUE value
iiiii is INTENSITY value

- Send GETHSIxx to retrieve Hue data for LED xx (01 = fiber 1, 02 = fiber 2 etc.).
Analyser responds with hhh.hh sss iiiii where
hhh.hh is the HUE value (with two decimal digits)
sss is the SATURATION value
iiiii is INTENSITY value
Does the LED Analyser work with Labview?
Yes. We provide a library of Virtual Instrument (Vi) files for use with Labview. The library is available on the CD supplied with each unit. Alternatively you can contact us for access to our download section on the website.
What Software will the LED Analyser work with?
Basically any software that can send and receive basic ASCII string commands over the communications (RS232 or USB) port can communicate with the LED Analyser. We provide and extensive library including DLL’s and example routines for many of the common software platforms such as C++, C#, VB etc.
Is there a CAD Drawing of the Optical Heads available?
Yes. Please contact us and we can forward you a .stp file for the Optical Heads.
How do I know the Optical Fibre is correctly inserted into the Optical Head?
Unscrew the Cap of the Plastic Fibre retainer on the top of the Optical Head. Insert the Fibre into the holder and push it all the way to the end stop. Hand tighten the cap to hold the fibre in place.
How do I mount the Fibre over the LED?
Please refer to the Fixturing Guidelines document provided on the CD. Alternatively contact us and we will send you the document by email.
How do I mount the Optical Head over the LED?
Please refer to the Fixturing Guidelines document provided on the CD. Alternatively contact us and we will send you the document by email.
Is 20 the maximum number of LEDs that I can test?
While 20 Channels is our largest single module you can use the “Daisy Chain” function to connect additional Analysers and control them over a single communications port. On the DaisyChain all LEDs are measured simultaneously. Please refere to the Daisy Chain section of the User Manual.
How are the over range and under range conditions displayed?
When the Intensity level measured by a particular channel is out of the range (too low or too high) the LED Analyser displays the following:

Under range: 000 000 000 00000 Over range: 255 255 255 99999

Under range: 999.99 999 00000 Over range: 999.99 999 99999

Under range or over range: 0.0000 0.0000

Under range or over range: 00000 +0.5555

Under range or over range: 000