Handheld Photosynthesis System


Product Details


  • Go to and download the libusb-win32 driver. Open the "Bin" folder. Run the "inf-wizard.exe." If prompted that the driver is not published, verified or signed, continue installing anyways. Once the inf-wizard is installed, run the CI-340 software. This .dll error occurs mainly on computers with 64 bit operating systems.

  • If the Tleaf value is a large negative number (ex: -149 degrees Celcius), check that the temperature sensor is fully connected to the instrument. Often disconnecting the IR temperature sensor and then reconnecting it and powering the unit on again will correct the extreme negative reading. If the value does not change, try testing the sensor by holding it in your hand to warm it slightly and seeing if this increase is shown in the measurements.

  • This indicates that the leaf you are sampling is not actively photosynthesizing or using CO2. The plant could be photosynthesizing at low rates or be in a state of respiration.

  • The latest version of software, the driver, and firmware codes can be downloaded at Use the serial number located on the underside of the instrument and whether the unit has an RS232 or USB connection to select the correct download.

Soda lime does have a PH-sensitive Ethyl Violet color change indicator, but this is weak and typically doesn't change color strongly even though the soda lime has lost strength.  Adsorption of CO2 by soda lime requires moisture, so if the soda lime has dried out this will reduce scrubbing capabilities.  

You can test your soda lime by connecting it to the CI-340 intake.  Start a measurement in Single Channel Absolute mode (S) so you are simply reading the CO2IN value.  Blow into the tubing going into the soda lime column and watch the CO2IN reading on the CI-340 to see if it increases. There will be a lag time while the sample from your breath travels through the soda lime and tubing to the CO2 IRGA sensor.   If the CO2 IN rises up, the soda lime is probably exhausted and needs replacement.  

To refresh soda lime, try adding a small amount of water to the bottom of the soda lime/desiccant column.  You should not add more than 5 cc of water at a time.  Be sure to replace the cotton filter at either end of the plastic column of soda lime.   Repeat the breath test to see if the soda lime improves at scrubbing CO2.  If not, replace the soda lime with fresh and test again.  

The CI-340 photosynthesis system can store approximately 25,000 counts or measurements in the 4 MB of internal memory.  

When using the AD module, the CI-340 will not record a measurement until the CO2 in source is stabilized. Proper purging methods are required to stabilize the CO2 stream into the instrument as well as sufficient CO2 gas in the CO2 canister.

  1. Open up the desired manual in a browser window 
  2. Click ‘Accessibility Mode’ 
  3. Select the download icon. The manual will download as a pdf. 

There is a single CO2 IRGA in the CI-340, this means that the instrument first must measure the CO2 level at the intake and then it switches over to measure the CO2 exiting the leaf chamber.  

The analyzer measures the intake for approximately 20 seconds, first. These measurements are sent to a microprocessor that averages these readings and corrects them for any non-linearity present in the analyzer. A relative value of CO2 concentration is continually updated by the microprocessor. The time interval set by the user at the beginning of the measurement dictates how long the measurement is taken and the concentration then averaged by the microprocessor. This time set by the end user is typically 10-20 seconds. Finally, the CO2 exiting the leaf chamber is measured by the analyzer for 20 seconds. This means that a complete single measurement takes approximately 45-60 seconds.  

If you are experiencing unstable measurements from the CI-340, the most common cause is an unstable CO2 in source. Make sure you are using the filter and tubing on the intake of the instrument to get the intake away from human respiration or other varying sources of CO2. Alternatively, use a buffer system for your CO2 intake. See “How Do I Make a Buffer Tank System?” FAQ for more information on this process.

How to Make a Buffer Tank System 

  1. Find and clean an empty bottle with cap, which is at least 3L in volume. 
  2. Drill two small holes in the cap of the buffer bottle:  1 hole is for the intake tube and 1 hole is for the out tubing. 
  3. Insert a short plastic tube into the cap of the buffer bottle for the “out”.   
  4. Insert a longer plastic tube into the cap of the buffer bottle that will connect to the “IN” of the instrument.  Use hot glue or otherwise seal the tubing to the cap, with no leaks.   
  5. Make sure that the tube and cap has no leaks. 
  6. Connect the “in” tubing to the intake port on the instrument. 
  7. To use the buffer bottle, make sure that the tubing is clear from obstruction.  Connect the In tubing to the unit.  Place the buffer bottle in a location that has stable CO2 concentration (away from operator, cars, furnace, photosynthesizing plants). 

For a guided FAQ, including pictures, click here.

While the device is powered off, hold down the 'up' arrow and turn the CI-340 on, continuing to hold the button down. Once powered on, the instrument will be in 'developer' mode.

Align the slots on the adapter with the slots on the back of the CI-340. Slide the adapter forward so that the pads make contact with the pins on the CI-340.