Using sensors

The 8200-104 Opaque Long-Term Chamber and 8200-104C Clear Long-Term Chamber can integrate many different kinds of sensors for the collection of ancillary data. Compatible sensors include: the chamber thermistor, the LI-190R Quantum Sensor, the LI-200R Pyranometer, and sensors with an SDI-12 interface, such as the Stevens HydraProbe.

Chamber Connection Allowances
Sensor Type Number of Sensors
Light 1 (the LI-190R Quantum Sensor or the LI-200R Pyranometer)
Chamber air temperature 1 (the integrated chamber thermistor)
SDI-12 Up to 9 with T-split fitting

Note: SDI-12 sensors require some configuration before they can be used. Sensor configuration is done using the SDI-12 console in the user interface. See SDI-12 console for details on configuring an SDI-12 sensor.

Connecting a sensor

LI-COR long-term chambers use a keyed Turck fitting to connect to a sensor. Sensors can be connected to any port of the chamber or T-split fitting. To connect a sensor, insert the female fitting of the sensor into the male fitting of the chamber or sensor T-split, then thread the connector until snug. The fittings are keyed, so be sure to align the key of the sensor fitting with the slot on the chamber or T-split fitting. The connection will not fit otherwise.

Using the sensor T-split fitting

The sensor T-split fitting (part number 310-18516) expands the number of sensors you may have connected to a LI-COR long-term chamber. Each T-split fitting can connect two sensors, including the chamber thermistor. Using the sensor T-split fitting is similar to connecting a sensor itself. One fitting of the T is a female fitting that you connect to the chamber and the additional fittings are male to connect to the sensors (see Figure 4‑7). The fittings are keyed, so be sure to align the key on one fitting with the slot on the other before tightening the threads.

Figure 4‑7. One end of the sensor T-split fitting connects to the chamber and the other two fittings are available to connect to a sensor.

Light sensors

Below are instructions for installing and maintaining the LI-190R Quantum Sensor and the LI-200R Pyranometer. Both sensors use the same instructions, except each has its own sensor block in the configuration. The quantum sensor package (part number 190R-8200) and the pyranometer package (part number 200R-8200) include a mounting plate and leveling stake used to mount and level the sensor.

Note: The LI-190R Quantum Sensor and LI-200R Pyranometer are the only light sensors compatible with the 8200-104/C Long-Term Chambers. Only one light sensor may be connected to a chamber at a time.

LI-190R Quantum Sensor

The LI-190R Quantum Sensor can be connected to the 8200-104/C Long-Term Chambers to measure photosynthetically active radiation at the chamber to supplement your data.

  Quantum Sensor Specifications
Spectral Response: 400 to 700 nm
Energy Range: 0 to 2000 μmol/m2/s
Absolute Calibration: ±5%
Output Signal: 0 to 15 μA
Linearity: Max. deviation of 1% up to 10,000 μmols-1m-2
Cosine Correction: Up to 82° angle of incidence
Azimuth Error: <1% over 360° at a 45° elevation angle

LI-200R Pyranometer

The LI-200R Pyranometer can be connected to the 8200-104/C Long-Term Chambers to measure global solar radiation at the chamber to supplement your data.

  Pyranometer Specifications
Spectral Response: 400 to 1100 nm
Energy Range: 0 to 1000 W/m2
Absolute Calibration: ±5%
Output Signal: 0 to 75 μA
Linearity: Max. deviation of 1% up to 3,000 W m-2
Cosine Correction: Up to 82° angle of incidence
Azimuth Error: <1% over 360° at a 45° elevation angle

Installing the sensor

Installing the sensor takes just a few steps.

  1. Choose a position for the sensor so that it will not be shaded, from either the surrounding landscape or the chamber itself, and so that the sensor and its cable will not interfere with the chamber opening and closing.
  2. Push the leveling stake into the soil keeping it as upright as possible.
  3. Leave at least 5 cm of clearance between the soil and the bottom of the mounting plate to prevent the sensor from being submerged in heavy rain. If the soil is difficult to push the stake into, you can drive the stake into the soil. Set a scrap piece of wood into the opening between the arms and tap the wood using a hammer or mallet. Be careful not to bend the stake.
  4. Attach the mounting plate to the leveling stake using the three Phillips-head screws.
  5. Do not fully tighten the screws at this point.
  6. Mount the sensor in the fixture on the mounting plate by placing the sensor into the fixture and tightening the mounting screw against the sensor base.
  8. Level the sensor by adjusting the three hex-head leveling screws until the bubble is centered in the bubble level.
  9. Fully tighten the Phillips-head screws from step 3 to lock the mounting plate in place.
  10. Connect the sensor to the chamber using the instruction in Connecting a sensor.

Configuring the sensor

LI-COR sensors require little configuration to work with the LI-8250 Multiplexer.

  1. To add a sensor to a LI-COR chamber block, first navigate to Configuration in the LI-8250 Multiplexer user interface.
  2. If you do not have an existing configuration, see Configuring the LI-8250 Multiplexer block for details on how to do this.
  3. Expand the Sensor Library drop-down and select LI-COR.
  4. Click and drag the LI-COR LI-190R or LI-COR LI-200R block under the chamber where it will be added.
  6. You will then need to add the Serial Number and LI-COR Light Sensor Multiplier for your sensor.
  8. Each LI-COR radiation sensor is shipped with a certificate of calibration. The certificate can also be found at licor.com/env/support/. Enter your sensor's serial number in the calibration search box at the bottom of the page. The calibration multiplier is listed on the certificate under For use with LI-COR handheld meters and loggers.

Maintaining the sensor

  • Keep the surface and vertical edge of the acrylic diffuser clean.
  • Clean the diffuser sensor with water, mild detergent, or vinegar dilute using a soft, lint-free cloth as needed.
  • Do not use alcohol, organic solvents, strong detergents, abrasive solvents, or abrasive cloth on the diffuser.
  • Return the sensor to LI-COR for factory recalibration every two years. Contact technical support for more information.

Stevens HydraProbe II

The Stevens HydraProbe provides ancillary soil moisture and temperature data from the probe measured alongside soil gas concentration data. The probe communicates with the LI-8250 Multiplexer using the SDI-12 communications protocol. Provided are some basic instructions for installing and using the Stevens HydraProbe. For more information about using the Stevens HydraProbe, see the operation instructions at: https://stevenswater.com/products/hydraprobe/

  Stevens HydraProbe II Specifications
Operating Temperature Range: -10 to 60 °C
Voltage Range: 9 to 20 VDC
Measurement Range: 0 to saturation
Accuracy: ±0.03 m3/m3
Power Requirements: <1 mA idle; 10 mA active

Installing the sensor

Install the probe by burying it in soil that is representative of your site.

  1. Choose a position for the probe so that the probe cable will not interfere with the chamber opening and closing.
  2. Dig a small hole with a smooth, undisturbed side.
  3. Try to keep the excavated soil as an intact block if possible.
  4. At a depth of 5 cm below the soil surface, press the probe into the soil until the base of the tines are flush with the side.
  5. Be especially careful to avoid creating air pockets when inserting the probe. Air pockets around the tines will reduce the accuracy of measurements.
  7. Replace the excavated soil, burying the probe.
  8. Connect the sensor to the chamber using the instruction in Connecting a sensor.

Configuring the sensor

Before you can configure a Stevens HydraProbe, it is recommended that you first change the address and the soil type and verify the measurement configuration using the instructions in Configuring a Stevens HydraProbe. Once you have done this, you can add the sensor to your configuration.

  1. To add a sensor to a LI-COR chamber block, first navigate to Configuration in the LI-8250 Multiplexer user interface.
  2. If you do not have an existing configuration, see Configuring the LI-8250 Multiplexer block for details on how to do this.
  3. Expand the Sensor Library drop-down and select Stevens.
  4. Click and drag the Stevens HydraProbe II block under the chamber where it will be added.
  6. Change the Sensor Address to the address you assigned the sensor using the SDI-12 console.
  7. The Measurement Set should be left at its default settings: SWC is measurement # 1 (for soil moisture) and TS is measurement # 3 (for soil temperature).
  9. One measurement block is needed for each variable logged by the probe. Two default blocks are included and do not need to be changed: SWC is for soil moisture (the first default output) and TS is for soil temperature (the third default output).
  10. To add more blocks, select the current block and duplicate it by pressing Ctrl + Shift + D or Cmd + Shift + D, or right-click the block and select Duplicate.
  11. Create a variable for the new measurement using the drop-down menu.
  12. The variable name you choose is how this measurement will be labeled in the files.
  14. Then select the Measurement # and the Units for the variable being logged.

Maintaining the sensor

The Stevens HydraProbe is sealed after calibration and does not require routine maintenance. However, be mindful of the following points.

  • Read and understand the manufacturer’s instructions provided with this product.
  • Do not attempt to disassemble the probe. This will damage the factory seal and invalidate the warranty.
  • Do not remove the HydraProbe from the soil by pulling on the cable.
  • Do not attempt to straighten a bent tine while it is attached to the probe.

Generic sensors

The LI-8250 Multiplexer can integrate data from nearly any sensor that uses an SDI-12 interface. LI-COR offers an optional 2 m sensor connector (Turck) to cable with flying leads (part number 392-18518) to connect an SDI-12 sensor to the 8200-104/C Long-Term Chambers. See Sensor connector pin assignments for a diagram and details of the cable pin assignment.

Caution: Be certain when wiring an SDI-12 sensor using the sensor connector to cable with flying leads not to connect, short, or allow water to make contact with the white or gray wires. If the white or gray wires are connected, shorted, or make contact with water, all sensor communications may be corrupted, including the light sensor and thermistor temperature measurements.

Installing the sensor

Install the sensor according to the manufacturer's instructions choosing a position for the sensor so that the sensor and its cable will not interfere with the chamber opening and closing. Then connect the sensor to the chamber using the instruction in Connecting a sensor.

Configuring the sensor

Before you can configure an SDI-12 sensor, it is recommended that you first change the address and configure the sensor using the SDI-12 console. Using the console to configure sensors is detailed in SDI-12 console. Refer to the documentation provided with your sensor for details on configuring it. Once you have done this, you can add the sensor to your configuration.

  1. To add a sensor to a LI-COR chamber block, first navigate to Configuration in the LI-8250 Multiplexer user interface.
  2. If you do not have an existing configuration, see Configuring the LI-8250 Multiplexer block for details on how to do this.
  3. Expand the Sensor Library drop-down and select Generic Sensors.
  4. Click and drag the SDI-12 Sensor block under the chamber where it will be added.
  6. Give the sensor a name and change the Sensor Address to the address you assigned the sensor using the SDI-12 console .
  7. The Measurement Set represents the measurement configuration chosen for the sensor in the SDI-12 console.
  9. Within the measurement block, use the MEASURE drop-down to Create a variable to be measured. The variable name you choose is how this measurement will be labeled in the files.
  11. One measurement block and variable is needed for each variable logged by the sensor. To add more blocks, select the current block and duplicate it. To duplicate a block, select it and press Ctrl + Shift + D or Cmd + Shift + D, or right-click the block and select Duplicate.
  12. Select the Measurement # of the variable you would like logged.
  13. The Measurement # is a numbered output based on the Measurement Set you configured in the SDI-12 console. For example, on the Stevens HydraProbe Measurement # 1 is soil moisture when using the default configuration.
  14. Select the Units for the variable being logged.

Viewing live data from the instruments

Sensor data can be viewed live in the LI-8250 Multiplexer user interface under Real Time Variables. It is good practice to verify that the sensor and sensor measurements are behaving as expected after you have configured your sensor.

To see sensor data, go to the Home page. In the Real Time Variables pane, expand the drop-down menu and choose the variable(s) from the sensor you would like to see. Selecting a variable from the drop-down menu will add that variable to your Real Time Variables list. Clicking on the trashcan of a variable will remove that variable from your list.

With the variable(s) added to your list, use the Active Port drop-down menu to select the chamber with the sensor. Data, including sensor data, will begin streaming from the chamber on that port. This data can also be seen when a sequence is running but only from the currently active port.

Note: Different sensors have different measurement rates, so the time will vary for when you can begin to see data. For example, the thermistor and light sensors are measured once per second but some SDI-12 sensors provide one measurement per minute.