Using sensors at chambers

Long-term chambers support a variety of sensors for the collection of ancillary data. Compatible sensors include the built-in chamber thermistor, the LI-190R Quantum Sensor, the LI-200R Pyranometer, and sensors that support the SDI-12 protocol, such as the Stevens HydraProbe.

Sensor Type	Number of Sensors
Chamber air temperature	1 (built-in chamber thermistor)
Light	1 (LI-190R Quantum Sensor or LI-200R Pyranometer)
SDI-12	Up to nine with T-split fittings

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 Using the SDI-12 console for details on configuring an SDI-12 sensor.

LI-COR long-term chambers use a keyed connector for sensors. Sensors can be connected to any port of the chamber or T-split fitting. To connect a sensor, align the key and then tighten the connector. Press and turn the connector until it is fully seated.

LI-190R and LI-200R light sensors

Below are instructions for installing the LI-190R Quantum Sensor and the LI-200R Pyranometer. Both sensors are connected the same way, 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.

The LI-190R Quantum Sensor measures photosynthetically active radiation at the chamber. The LI-200R Pyranometer measures total solar radiation at the chamber.

Field installation

Installing the sensor takes just a few steps.

1. Connect the sensor cable to the a connector on the chamber.

2. Install the light sensor in the base and attach the base to the mounting post.

   Keep both the leveling screws (hex key) and plate mounting screws (Phillips) loose for now.

3. Push the leveling stake into the soil.

   Choose a position that does not interfere with the chamber opening, is not under artificial shade, and prevents risk of the cable getting in the way. Keep the stake vertical so the light sensor is close to level. Leave at least 5 cm of clearance between the soil and bottom of the mounting plate. You can drive the stake using a mallet - place a piece of wood in the cutaway section of the stake so you do not strike the metal with the mallet.

4. Level the sensor.

   Starting with the mounting screws loose, adjust the leveling screws to level the light sensor. Then tighten the mounting screws.

Configuring the light sensor

Light sensors are calibration constants are entered in the Configuration workspace. You will enter a unique multiplier for each sensor. You can also enter the serial number for good record keeping. This procedure depends on having completed the steps in Getting started, and having chambers as part of the configuration. To configure the sensor:

1. In the Configuration workspace, inside a specific Chamber block, add a light sensor block (under Sensor Library, select either LI-190R or LI-200R).

2. Enter the Serial Number and LI-COR Light Sensor Multiplier for each sensor.

   Chambers are identified by the serial number in the interface.

   

Each LI-COR light sensor is shipped with a certificate of calibration, which can also be downloaded from licor.com/env/support/. The calibration multiplier is listed on the certificate under For use with LI-COR handheld meters and loggers.

Stevens HydraProbe

The Stevens HydraProbe provides soil moisture and temperature data from the site. The probe communicates with the LI-8250 Multiplexer using the SDI-12 protocol. Here we provide basic instructions for using the Stevens HydraProbe. For more information about using the Stevens HydraProbe, see the operation instructions at: https://stevenswater.com/products/hydraprobe/

Field installation

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

1. Connect the sensor cable to a connector on the chamber.

   Choose a position for the probe so that the cable will not interfere with the chamber opening and closing.

2. Dig a small hole with a smooth, undisturbed side.

   Try to keep the excavated soil as an intact block, if possible.

3. 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.

   Be especially careful to avoid creating air pockets when inserting the probe. Air pockets around the tines will reduce the accuracy of measurements.

   

4. Replace the excavated soil, burying the probe.

Configuring the sensor

This procedure depends on having completed the steps in Getting started, and having chambers as part of the configuration. It also depends upon each Stevens HydraProbe having a unique address and the soil type specified, as described in Using the SDI-12 console. Once you have done this, you can add the sensor to your configuration. To configure the sensor:

1. In the Configuration workspace, inside a specific Chamber block, add a Stevens HydraProbe block (under Sensor Library).

2. 
2. Change the Sensor Address to the address you assigned the sensor using the SDI-12 console.
3. See Using the SDI-12 console to configure addresses. 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). One measurement block is needed for each variable logged by the probe. Two blocks are added by default: SWC is for soil moisture (the first default output) and TS is for soil temperature (the third default output).
3. 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.
4. Create a variable for the new measurement using the menu.
5. The variable name you choose is how this measurement will be labeled in the files.
6. 
7. Then select the Measurement # and the Units for the variable being logged.

Generic sensors

The LI-8250 Multiplexer can record data from others sensors that use the SDI-12 protocol. LI-COR offers an optional 2-meter cable with a connector and bare leads (part number 392-18518) to connect an SDI-12 sensor to the 8200-104/C Long-Term Chambers. Pin assignments shown in Table 3‑1 represents the connector pins.

Table 3‑1. Pin assignments and wire colors for the chamber sensor connector.

	Connector Pin #	Function	Wire Color
	1	+12 VDC power	Brown
	2	Thermistor input	White
	3	SDI-12 data	Blue
	4	Ground	Black
	5	Current input (light sensors)	Gray

Caution: Be certain when wiring an SDI-12 sensor using the cable with bare 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 cable to the chamber.

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 Using the 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 Multiplexer and component blocks for details on how to do this.
2. Expand the Sensor Library menu and select Generic Sensors.
3. Click and drag the SDI-12 Sensor block under the chamber where it will be added.
4. 
4. Give the sensor a name and change the Sensor Address to the address you assigned the sensor using the SDI-12 console .
5. The Measurement Set represents the measurement configuration chosen for the sensor in the SDI-12 console. Within the measurement block, use the MEASURE menu to Create a variable to be measured. The variable name you choose is how this measurement will be labeled in the files.
6. 
7. 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.
5. Select the Measurement # of the variable you would like logged.
6. 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.
6. Select the Units for the variable being logged.

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. One connector connects to the chamber; the others connect to the sensors (see Figure 3‑6). The connectors are keyed, so be sure to align the key on one connector with the slot on the other before tightening. Then press and tighten until the it is fully tightened.