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Fluorescence-Control Unit

From Bioblast


O2k-Open Support

Fluorescence-Control Unit

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MitoPedia O2k and high-resolution respirometry: O2k-Open Support 


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Fluorescence-Control Unit with O2k-Front Fixation, Current-Control (O2k-Chamber A and B) for regulation of light intensity of the LED in the fluorescence sensors. This item is a standard component of the O2k-Fluorescence LED2-Module.

Reference: >> More details? Consult O2k-Fluorescence LED2-Module


Setup of the O2k-Fluorescence LED2-Module

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  • Switch off the O2k with the power switch on the rear of the O2k-Main Unit.
  • Remove both blue O2k-Window Frames. Insert the O2k-Window Tool around the outer rim of the window frame and unscrew counter clockwise.
  • Remove the Sensor-Guide (β€˜nose’) from the O2k-Front Fixation of the Fluorescence-Control Unit.
  • Place the Fluorescence-Control Unit below the O2k-Chamber Block. Align the windows of the O2k-Front-Fixation with the windows of the O2k-Chamber Block, re-insert the O2k-Window Frames, and screw them finger-tight onto the O2k-Main Unit.
  • Re-attach the Sensor-Guide to the O2k-Front-Fixation. (There is no need to use the fixation screw supplied with early models).
  • Place the power-cables from the rear of the Fluorescence-Control Unit in the middle below the O2k-Main Unit from front to rear. Unplug the mains power cable of the O2k and plug it into the female plug of the Fluorescence-Control Unit. Insert the male plug of the Fluorescence-Control Unit into the mains socket at the rear of the O2k.
  • Connect the amperometric cables attached to the side of the Fluorescence-Control Unit to the β€˜Amp’ plugs (labeled "NO" in Series D-E) on the O2k-Main Unit.
In this configuration the O2k can be used for high-resolution respirometry and fluorometry. It is not necessary to dismount the Fluorescence-Control Unit for basic HRR when a fluorescence signal is not recorded.

O2k-Guide: Setup - next step - Selecting a Fluorescence Sensor
O2k-Guide: Setup - next step - Mounting a Filter-Cap

Power on

  • Switch on the power of the O2k-Main Unit (rear).
  • Press the power switch on the front panel of the Fluorescence-Control Unit. Check that the two red/green control lights (O2k-Fluorescence LED2-Module B and upwards) or the central green control light are on.

The Oxygraph Window

O2k control window, Amp. section
  • From the DatLab menu choose [Oxygraph]/[O2k-Control].
In the Configuration Table of the Oxygraph Control window, the used sensor can be entered for documentation purposes.
In the Control Table of the Oxygraph Control window the LED intensity and the gain (amplification) can be set.

Control of LED-intensity

The light intensity of the LEDs is set by the current control, independent for each fluorescence sensor (O2k-Chamber A and B). The current is controlled by DatLab in a very wide range for optimization according to sample and fluorophore requirements. At higher LED-intensity the optical sensitivity is increased, i.e. the signal change per concentration change is enhanced. However, even moderately intensive light may exert negative effects: (i) Damage to the sample reducing the biological activity. (ii) Damage to fluorophores catalyzing degradation and various side reactions. Therefore, the LED-intensity should be kept as low as compatible with a smooth signal, i.e. when the resolution is just not limited by noise or disturbances. The values indicated in the table application specific settings are only suggestions to start with. It is recommended to optimize the light intensity specifically for each application.
Setting the LED Intensity from DatLab: O2k-Fluorescence LED2-Module Series B and higher (modules without mechanical selector switch)
  • Set the desired light intensity (0 to 2000) in the field "Amp Polarisation Voltage [mV]".
  • Click "Send to Oxygraph" or "Connect to Oxygraph-2k" to apply the new settings
  • If any current >= 0 is set and the Fluorescence Module is switched on, the indicator light below the respective chamber on the Fluorescence-Control Unit will be green. If the current is zero (the LED is not used) but the Fluorescence-Control_Unit is switched on the indicator light will be red.
Limitations: For Series D oxygraphs the LED intensity has to be set to the same value for both chambers.
Note: The actual current (in mA) used to drive the LED is the value set in DatLab (Amp polarization voltage) divided by 100.
Previously we quoted the suggested current. To simplify the operation we now state directly the required DatLab settings.
Setting the LED Intensity from DatLab: O2k-Fluorescence LED2-Module Series A (modules with mechanical selector switch)
Series A of the O2k-Fluorescence LED2-Module has a mechanical selector switch for each chamber on the front side of the Fluorescence-Control_Unit
  • Bring the switch on the front panel of the Fluorescence- Control Unit into position 9 (use the small supplied screw driver)
  • Follow the procedure described above for Series B and higher.
For LED2-Module Series A it is still possible to set the LED current directly at the Fluorescence-Control Unit. However, this less convenient method is obsolete. The relevant instructions can be found on the discussion page in the archive.
Conversion of the LED intensities between the Fluorescence-Sensor of the O2k-Fluo LED2-Module (O2k-Series D to G) and the Smart Fluo-Sensor of theO2k-FluoRespirometer (O2k-Series H)
  • The O2k-FluoRespirometer (O2k-Series H-I) and software DatLab 7, the fluorescent intensity (excitation) of the Smart Fluo-Sensors is set in 'Fluo intensity' units. The Smart Fluo-Sensors are precalibrated to guarantee similar fluorescence intensity among Smart Fluo-Sensors of the same colour, storing the sensor-specific 'gain value' in an internal memory. Technically speaking, DatLab 7 (firmware) (i) reads this 'gain value' from a connected Smart Fluo-Sensor to adjust the output intensity and (ii) automatically corrects for the non-linear relationship between intensity and mV to output the correct fluorescent intensity. In contrast, the fluorescent intensity (excitation) of the Fluorescence-Sensors of the O2k-Fluo LED2-Module (O2k-Series D to G) is set directly in 'mV' units. To set the same intensity for O2k-Fluo LED2-Module (O2k-Series D to G) Fluorescence-Sensor as for a O2k-FluoRespirometer (O2k-Series H-I) Smart Fluo-Sensor, we have created an Excel worksheet to calculate it.
Download2.png Download the EXCEL calculation-sheet to adjust fluorescence intensity


The gain for the Amp channel can be set in the Control Table of the Oxygraph Control window, the section β€œAmp” to 1, 10, 100, or 1000. The gain setting will influence the Amp raw signal recorded in Volt. See Observing the Fluorescence Signal. The amplified signal can be recorded in the range -10 to +10 V.
The gain setting should be chosen to obtain a maximum signal well below 10 V. If the maximum observed raw signal was 9 V in an initial experiment, then the gain should be reduced to avoid "off scale" (>9.99 V). On the other hand, if the maximum recorded raw signal was considerable lower than 1 V (e.g. 0.2 V), the gain can be increased to avoid limitation of resolution by digital noise.
Note for advanced users: At gain 1, a current of 1 nA is recorded as a voltage of 1 mV (0.001 V). At gain 100, 1 nA corresponds to 100 mV (0.1 V), as can be seen form the table below:
1 pA at sensor
1 mV recorded
Digital resolution
mV recorded
pA at sensor

O2k-Guide: O2k-Fluorescence_LED2-Module#DatLab-Analysis

MitoPedia O2k and high-resolution respirometry: O2k hardware, O2k-Open Support, O2k-Respirometry, O2k-FluoRespirometry