Independent Control of LED Output

The 6400-18 features LEDs with independent control of the intensity and percent of red, green, and blue light. White light can be achieved by using equal proportions of red, green, and blue. Select any intensity (to 2000 μmol m^-2 s^-1) of a pre-defined color, or define your own blended color, by selecting the proportion of red, green, and/or blue light to be applied to the sample. As an example, for stomatal kinetics studies, you could measure stomatal conductance with 100% red, 100% green, and 0% blue, as compared to using 100% blue light. The 6400-18 can also be easily configured to emulate the output of the 6400-02B Red-Blue Light Source for comparison studies.

Careful Design and Calibration

The LED tile in the 6400-18 is configured to ensure uniform light distribution at the leaf surface. LEDs minimize the influence of the light source on the leaf environment, as they have low heat generation compared to other light sources. The 6400-18 is calibrated on an integrating sphere by measuring total output and spectral quality with a spectroradiometer. The output is used to calibrate a silicon feedback photodiode built into the light source (below). The feedback photodiode ensures an accurate light intensity by adjusting the light source as required. The light source also has temperature correction and linearization circuitry that are calibrated as well, to ensure the accuracy of radiant output at all rated operating temperatures and intensities. The 6400-18 mounts easily to the 6400-17; the propafilm covered plate used with the Whole Plant Arabidopsis Chamber attaches directly to the Light Source. This method of attachment ensures that the geometry between the plant sample and the light source is repeatable for every measurement.

Software Automation

The 6400-18 is completely integrated with the LI-6400/6400XT. The light source intensity can be changed for light response curves, set to match external PAR sensor readings, or held constant while other environmental conditions are altered. Light and CO2 response curve autoprograms are built into OPEN software that can be used to automatically control and collect data for unattended curves. Simply set the desired chamber environmental conditions and light intensities from the 6400-18. The autoprogram prompts for the light levels at which measurements will be logged, the minimum and maximum time between measurements, and the stability parameter(s) that must be achieved before a measurement is logged. The 6400-18 light levels will be set, and all other environmental controls are maintained during the experiment. OPEN 6.1 (or above) software is required, which contains a dedicated configuration for the 6400-18 RGB Light Source. NOTE: OPEN 6.1 (or above) can be installed on 200 MHz (ver 5.x) or 400 MHz (ver 6.x) digital boards. Older boards require a digital board upgrade - contact LI-COR for details.

6400-18 RGB Light Source Specifications

Controllable Output Range (white): up to 2000 μmol m^-2 s^-1 at 25°C (typical)

Output Spatial Uniformity: ± 10% within 90% of output area

Power Consumption: ≤ 45 W at 2000 μmol m^-2 s^-1 (white light) at 25°C

Operating Temperature Range: 0 - 50°C

Operating RH: 0 - 95%, non-condensing

Size: 12.4H x 9.0W x 9.5L cm (4.9 x 3.6 x 3.7 in)

Weight: 0.54 kg (1.20 lb)

Note: Light output specifications listed are at the light source window at a temperature of 25°C. White light is referred to as equal quantum fluxes of red, green, and blue.