Insect respiration chamber

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See Removing a chamber to detach a currently-installed chamber.

The Insect Respiration Chamber (6800-89) is a column and adapter that allows you to measure gas exchange from small, discrete samples using the LI-6800. In this section we describe how to install the chamber and take measurements. The chamber uses the instrument pump to circulate air. The mixing fan is deactivated because laminar flow through the chamber provides adequate mixing.

Installing the chamber

  1. Install the chamber adapter.
  2. Tighten the screws snugly—until they are tight and then just a little bit more.
  3. Install the three stainless steel caps and two Swagelok fittings onto the chamber adapter.
  4. Cut two pieces of hose, each about 5 to 10 cm long. Remove the brass nuts on the air inlet and air outlet. Remove the brass ferrules and set them aside. Install a set of vinyl ferrules on each hose, as shown.
  5. Install the hoses between the chamber and the head, as shown.
  6. Air flows through the insect chamber while CO2 is measured by the LI-6800
  7. Verify that the chamber is recognized under Constants > System Constants.
  8. Run the Chamber Leak Test under Start Up > Warmup/System Tests. Correct any issues indicated by the test.
  9. Reinstall the connector cover.

Making a basic measurement

  1. Set the Environment controls:
    • Flow: Set Flow: On; Pump speed: Auto; Flow rate: 400 µmol s-1 or your desired flow rate; Press Valve: 0.0 kPa
    • H2O: Set H2O: On; RH_air: 50%
    • CO2: Set CO2 injector: On; Soda Lime: Scrub Auto; Tap CO2_r and enter a setpoint of 400 µmol mol‑1. If you are expecting large fluctuations in gas exchange, e.g., human breath cycles, it is best to control on CO2_r. One of CO2_r or CO2_s should always be stable when you make measurements.
    • Fan: Set Mixing fan: Off
    • Temperatures: Check the temperatures to see their current values
  2. Load the chamber.
  3. Disconnect one of the tubes (either Air Inlet or Air Outlet) and unscrew the corresponding cap from the chamber.
  4. Place the sample in the insect chamber
  5. Load the sample, replace the cap, and then reinstall the tube.
  6. Under Log Files > Open a Log File, create a new file or open an existing file. If desired, configure the software to Prompt on Log, which will allow you to enter the sample weight with each measurement.
  7. Take a measurement.
  8. Under Measurements, tap the Log button.