Taking Measurements

This section describes precautions, techniques, and procedures for taking measurements with the LI-600N.

Precautions and techniques

Observe these precautions and practice these techniques before and while taking measurements with the LI-600N.


To protect the LI-600N when not in use, turn it off and place it in the carrying case. Before using the LI-600N, take the following precautions.

  • Charge the battery. A fully charged battery provides approximately 8 hours of active use. See Charging considerations for charging time.
  • Attach and use the wrist strap. To protect the LI-600N, attach the wrist strap to the instrument and adjust it to your wrist size. Use the wrist strap at all times (or risk being "the person who dropped it").
  • Insert the USB port protector. To protect the USB port from debris, keep the protector inserted when the instrument is not connected to a computer.
  • Allow the instrument to come to ambient temperature. If you are moving the instrument to a site with a higher or lower temperature than it is stored in, wait fifteen minutes before taking a measurement so the instrument can acclimate.


Following these techniques helps ensure the quality and accuracy of your measurements.

  • Align the needle or leaf with the opening in the aperture. If they are not aligned, the IRT sensor will not accurately measure the sample.
  • Maintain the light conditions of the leaf. Do not alter the light on or shade the leaf you are measuring.1 If, while taking a measurement, you shade the leaf you plan to measure next, unshade the leaf and wait 60 seconds before measuring it. Changes to light at the leaf surface will affect PhiPSII and gsw.
  • Match the quantum sensor's light conditions to those of the leaf. If the leaf you measure is in the light, ensure that the quantum sensor is also in the light. If the leaf you measure is in shade, ensure that the quantum sensor is also in the shade. A mismatch between the leaf and the quantum sensor may result in a significant error in ETR calculation.
  • Avoid measuring a needle or leaf with water on it. If the needle or leaf you plan to measure has water or condensation on it, gently and thoroughly dry it. Measuring a wet needle or leaf may result in overestimation of stomatal conductance, and water ingress into the instrument may cause damage.
  • Maintain unblocked vents on the instrument. Do not cover any of the vents on the instrument when taking measurements.
  • Turn GPS off when not in use. GPS uses more power when it is searching for satellites. If you're indoors or in an area with poor satellite fix, turn off GPS to save battery power. GPS can be turned off on the instrument by going to Settings (left arrow from Select Configuration), or can be turned off in a configuration by leaving "Use GPS and Leaf Angle" unchecked in the General screen in Configuration Management.


The LI-600N comes with both lower aperture and upper clamp gaskets installed.

Clamp gaskets

The LI-600N includes three sets of clamp gaskets for use with needles and leaves of varying diameters.

Clamp gasket sizes

Depending on the diameter or thickness of the needle or leaf you're measuring, you may need to change the clamp gaskets before taking measurements.

Figure 3‑1. The LI-600N clamp with size 0 clamp gaskets installed.

Needles or leaves can be from 1–3.5 mm wide, and must be a minimum of 14.2 mm long to cross the aperture.

The diameter or thickness of the needle or leaf to be measured determines which clamp gaskets to use. The 0 gasket is for needles or leaves of up to 2.6 mm in diameter/thickness, and the 1 and 2 gaskets are for needles or leaves of up to 2.8 mm in diameter/thickness.

Cutting clamp gaskets

Additional clamp gaskets, included in the accessories kit (part number 6360-368), come uncut, as shown below. The numbers indicate the absence (0) or size (1, 2) of the notch on the bottom of the gasket.

Figure 3‑2. Uncut clamp gaskets, top and side views.

Cut the gaskets off using a sharp razor blade or pen knife. Carefully cut as close to the side of the gasket as you can without cutting into the gasket.

Figure 3‑3. Cutting the clamp gaskets.

Changing clamp gaskets

Remove the installed gaskets from the clamp. The material is pliable, and you can pull one side out of its notch and lift the gasket out. Store them in the ziplock bag.

Tip: Bring your patience; this can be fussy.

  1. With the cut side facing out, take a lipped edge of the gasket you want to install and push it into its notch on the clamp.
  2. Push the other edge inwards to fold the gasket until the other lipped edge can be pushed into its notch.
  3. If needed, use the tweezers (included in the accessories kit) to adjust the position of the gasket.
Figure 3‑4. Insert one lipped edge of the clamp gasket first.

If, when taking measurements, you have problems with high leak percent (especially if the chamber is empty), check again that these gaskets are fully seated.

Aperture gasket

The LI-600N comes with a spare aperture gasket (part number 6360-369). The aperture gasket may need to be changed after periods of heavy use.

Figure 3‑5. The aperture gasket on the instrument.

To remove the aperture gasket from the instrument, gently pull on one of the outside ends to slightly stretch the gasket over the edge of the aperture, then lift it off.

To install the new gasket, place one end of the gasket over an outer edge of the aperture, and stretch slightly to pull the other end over the other edge.

Figure 3‑6. The aperture gasket.

The gasket should cover the outer edges of the aperture.

Figure 3‑7. A cross-section view of the aperture gasket fitted onto the aperture.

For information on cleaning the gaskets, see External Cleaning.

Taking a measurement

The workflow for taking a measurement on the LI-600N will vary depending on two settings in the active configuration: whether Prompt to edit during measurements is enabled for leaf area or width, and whether Prompt on log is enabled for optional data labels.

Match mode

After selecting a configuration and at intervals specified in the configuration (default is 10 minutes), the instrument goes into match mode, as indicated on the instrument screen. In match mode, the instrument checks to make sure the RH sensors are reading the same.

The LI-600N performs two types of matches: valved and serial. Which type of match is performed depends on the leak percent of the chamber when it is empty. The leak percent varies depending on which clamp (top) gaskets are installed.

If the leak percent is lower than the leak maximum allowed for a good measurement, the LI-600N will prompt the user to ask if a leaf is in the chamber. If the user answers yes, the instrument prompts the user to remove the leaf. If the user answers no, the instrument waits 10 seconds and computes the match adjustment without the valve. This is a serial match. This match is most likely with the flat (0) or small-notch (1) gaskets.

If the leak percent is higher than the leak maximum, the LI-600N activates the match valve, waits 10 seconds, computes the match adjustment, then deactivates the match valve and goes to the measurements screen. This is a valved match. This type of match is most likely with the larger notch (2) gaskets.

Do not enter match mode with a needle or leaf in the chamber. Matching with something in the chamber will ruin subsequent measurements.

Measurement workflow

To take a measurement:

  1. Power on the LI-600N.
  2. Select a Configuration and press Enter. The instrument will go into match mode. Follow any match prompts that appear. The instrument will then go to the Measurement screen.
  3. Clamp to a needle or leaf. Watch for stability in the gsw variable.
  4. Press the Enter button (Log) to log the measurement when your stability criteria are met.
  5. Unclamp the needle or leaf. If the leaf width/area prompt and/or "prompt on log" are enabled, the Data labels screen will appear. Use the arrow keys and Enter button to edit the leaf area or width, and to select the values in the labels or scan a barcode. Select Done and press Enter to return to the Measurement screen.
  6. Add remark (optional). Press the right arrow (Mark) to add a remark. Select the remark and press the Enter button. You will go back to the Measurement screen.
  7. Press Enter (New) to initiate a new measurement.
  8. Repeat from step 3 for subsequent measurements.

When you're done taking measurements, press the left arrow (Home) to go back to the Select Configuration screen, then press the left arrow again to go to Settings. Select Shut down and press the Enter button to safely turn off the instrument.

Using the barcode scanner

To enable the barcode scanner for a configuration, see Support: LI-600N Porometer/Fluorometer.

You will scan a barcode either before or after a measurement is logged, depending on whether Prompt on log is enabled in the configuration (see Support: LI-600N Porometer/Fluorometer). If it is enabled, you are prompted to scan a barcode after each measurement. If it is not enabled, you can scan the barcode before a measurement by pressing the right arrow (Prompt) from the Measurement screen, and then selecting the barcode label. If you scan the barcode before a measurement, that barcode will apply to subsequent measurements until you scan another barcode.

To scan a barcode:

  1. At the Data labels screen, navigate to the barcode label and press the Enter button. The barcode prompt will appear.
  2. At the Scan Barcode prompt, pass the red light from the barcode scanner on the bottom of the instrument over the barcode. When it reads the barcode the LI-600 will beep and return to the Data labels screen and display characters from the scanned barcode..

The barcode scanner will time out after a few seconds. If this happens, repeat the process. When finished, navigate to Done and press Enter to return to the Measurement screen.

Viewing measurement data

Data from the most recent measurement appear on the Measurement screen after taking a measurement, and before pressing the Enter button for a new measurement. For information on configuring the variables shown on the Measurement screen, see Display Layout.