Q. What Types of LED's and Colours can be tested ?
A. Many types of LED can be tested ranging in colour from 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.
Q. Can Flashing, Blinking or PWM modulated LED's be Tested ?
A. 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.
Q. Can 7-Segment Display's be tested ?
A. 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.
Q. Can Bi-Colour and Tri-Colour LED's be tested ?
A. Yes, each colour should be turned on individually and its RGB or HUE value read back.
Q. Can Bargraph Displays be tested ?
A. 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.
Q. Can all LED's be tested simultaneously ?
A. 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.
Q. What Output Formats are available from the Unit ?
A. The Analyser can output results through the USB or RS-232 Serial port or through the Parallel port. The RGB, HUE, Saturation, XY Chromaticity and Intensity values of each LED can be output.
Q. How much time does it take to test 20 LED's.
A. The Standard Capture time is around 1 second. There are also other capture modes avaliable: Fast Capture Mode (which needs around 100 milliseconds to take a measure) and the PWM Capture Mode (which capture time depends of the frequency and duty cycle of the signal used to power the LEDs).
The sensitivity level of the LED Analyser sensor has also a small influence in the capture time.
Q. What is RGB ?
A. RGB stands for Red Green Blue. Each colour is split into the three primary colours and these values are output from the Analyser.
Q. What is HUE ?
A. 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 40 to 50. Orange is around 20 and Bright Yellow is around 65.
Q. How is the unit mounted in a Fixture ?
A. There are four mounting holes on the ICT unit which can be used to attach the Analyser to a Base Plate.
Q. What options are available to connect the unit to a PC ?
A. 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).
Q. How close to the LED should the fiber be mounted ?
A. 2mm is usually best. However, for bright LED's greater distances may be required.
Q. What is the minimum bend radius for the fiber ?
A. 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.
Q. How long can the fiber be in length ?
A. 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.
Q. What are the power requirements ?
A. 5-7V DC 200mA.
Q.. What does an output of 255 255 255 mean ?
A. Unit is over range. This is caused by the LED being too bright or the fiber is too close to the LED. Decreasing the the intensity of the LED will not affect the colour being measured.
Q. Why does a red LED which looks the same brightness as a green LED measure much
higher intensity ?
A. The Human Eye is less sensitive to red light so a Red LED can be brighter than it looks!
Q. What is the format of the serial protocol ?
A. The serial protocol used to communicate with the LED analyser is very simple. A Terminal emulator such as Microsoft Windows Hyper Terminal can be used to demonstrate the communication with the LED Analyser. The same commands can be used from any programming language.
The settings are as follows RS232 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:
- Send SNE to the Led Analyser to trigger data capture. The system responds with S
- Send SPxxE to retrieve RGB data for LED xx (01 = fiber 1, 02 = fiber 2 etc.).
Analyser responds with SPrrrgggbbbiiiiiE where
rrr is RED value
ggg is GREEN value
bbb is BLUE value
iiiii is INTENSITY value
- Send SHxxE to retrieve Hue data for LED xx (01 = fiber 1, 02 = fiber 2 etc.).
Analyser responds with SHhhhhhE where
hhhhh is the hue value |
