Configuring the LI-8250 Multiplexer block

When you first open the Configuration page, you will see two empty root blocks: the LI-8250 Multiplexer block and the Sampling Sequence block. This section covers how to configure the LI-8250 Multiplexer block. For details on how to configure the Sampling Sequence block, see Configuring the Sampling Sequence block.

Tip: When configuring a system with multiple chambers and extension manifolds, you can copy/paste or duplicate blocks to speed things up (see Workspace actions).

1. Add a gas analyzer

Select Gas Analyzers from the Toolbox to open the drawer. Then select the gas analyzer model (LI-870, LI-7810, and so on) to add it to the configuration. Repeat this for each analyzer on the system. For Trace Gas Analyzers, you also need to click the Hostname menu and select the analyzer.

All gas analyzer blocks are nested under the LI-8250 Multiplexer block.

  • If you are using a LI-COR cable assembly for the Trace Gas Analyzers (part number 9982-011) or the LI-870 CO2/H2O Analyzer (part number 9982-010), the tubing length is set automatically.
  • If you have multiple gas analyzers connected using the T-split tubing (part number 9982-073), you will need to add 15 cm to the tube length for each analyzer.

2. Add a port

Before you can add an extension manifold or chamber, you will need to add the port that the device is connected to. To do this, select Multiplexer from the Toolbox, then click and drag Port # to place the block under the LI-8250 Multiplexer block.

You can assign a port number or the user interface will automatically assign a port number as these blocks are added. You can also provide a description of the devices on that port that will appear in the data file.

3. Add an 8250-01 Extension Manifold (optional)

This step is only necessary when an 8250-01 Extension Manifold is connected to your LI-8250 Multiplexer. If you do not have an extension manifold, skip to step 4.

To add an 8250-01 Extension Manifold, select Multiplexer from the Toolbox, then click and drag Extension Manifold to place the block under its respective Port # block. For example, if you have an extension manifold connected to port 2 of the multiplexer, place the extension manifold block under the Port # 2 block at the multiplexer level. Repeat this for each extension manifold.

Note: The 8250-01 Extension Manifold block will default to having one Port # block nested. If you have more than one chamber on that extension manifold, you will need to add additional Port # blocks under that extension manifold block.

4. Add a chamber

After you have added a port to the LI-8250 Multiplexer or 8250-01 Extension Manifold block, you can add a chamber to that port. The LI-8250 Multiplexer can interface with LI-COR long-term chambers and user-built custom chambers. This section will focus on adding LI-COR long-term chambers. For information about configuring a custom chamber see Integrating a custom chamber.

To add an 8200-104 Opaque Long-Term Chamber or 8200-104C Clear Long-Term Chamber, expand the Soil Chambers drop-down in the Toolbox and select LI-COR Chambers. Then click and drag either the 8200-104 Digital Long-Term Chamber or 8200-104C Clear Digital Long-Term Chamber block under the Port # block where you would like to add the chamber. Repeat this for each chamber on each port of the multiplexer and all extension manifolds.

Each LI-COR chamber block allows you to change several parameters. If you are using the cable assembly from LI-COR (part number 9982-056), the Tube Length of 1500 cm is correct. Collar Height must be measured and entered using the steps outlined in Measuring the collar height. You can also adjust the Pre-Purge, Post-Purge, and Observation Length according to your needs. See Terminology for additional details on these parameters. If the parameters chosen were not optimal, SoilFluxPro Software offers several tools to improve flux calculations in post-processing.

The LI-COR chamber block also allows you to attach a few other parameters. Location allows you to enter the location of the chamber and Open Position changes the position of the chamber when it is not taking a measurement. For details on changing the open position see Changing the open position.

Note: If a location is not defined, the multiplexer will use the GPS location of the LI-8250 Multiplexer as the chamber location in the data file.

To add these, select LI-COR Chambers in the Toolbox and find the Latitude/Longitude or Open Position blocks. Then click and drag the Latitude/Longitude or Open Position block to the chamber block.

5. Add a flux

Adding a flux to a LI-COR chamber block can be done in two ways. The first way is to select LI-COR Chambers from the Toolbox and find the Flux block. Then click and drag the Flux block under the chamber block you would like to add the flux to.

The other way to do so is to expand the Math drop-down and select Flux from the Toolbox. From the Flux drawer click and drag the block called Flux under the chamber you would like to add the flux to. For area-based flux enter the sample area (cm2). For mass-based flux, enter the sample mass (g) and volume (cm3). The sample volume is subtracted from the system volume.

The Flux block allows you to customize three additional parameters. The drop-down menu allows you to select the type of gas and the source for flux calculations. You can have multiple Flux blocks under each chamber depending on the analyzer(s) you are using and the gases you would like recorded.

You can also adjust the Deadband and Stop Time as needed. The Deadband and Stop Time are parts of the total Observation Length. Stop Time can be any time desired so long as it is beyond the Deadband and does not exceed the Observation Length. See Terminology to see how Deadband is defined.

Note: You will need one Flux block for each gas flux you would like to have computed. Without a Flux block, no flux will be calculated for that gas. If a Flux block was not added for a gas, a flux can still be calculated later using SoilFluxPro Software.

6. Add a sensor

LI-COR chambers can integrate various sensors for ancillary data, including the LI-190R Quantum Sensor, the LI-200R Pyranometer, the Stevens HydraProbe, and other SDI-12 sensors. How to install and configure a sensor is covered in detail in Using sensors. Here we will cover how to add the sensor to your chamber block.

To add a sensor to a LI-COR chamber block, expand the Sensor Library drop-down.

Generic Sensors allows you to add a generic SDI-12 sensor, Stevens allows you to add a Stevens HydraProbe II sensor, and LI-COR lets you add the LI-190R Quantum Sensor and the LI-200R Pyranometer. Click and drag the sensor under the chamber where it will be added.