Introduction to the LI-8250

Welcome, and thank you for your purchase of the LI-8250 Multiplexer. This document provides comprehensive operating instructions for the LI-8250 for soil gas flux measurements, flask measurements, and other applications. It describes soil chambers, gas analyzers, and accessories for the system, and it introduces SoilFluxPro Software, which is used to evaluate data collected by the LI-8250. If you have just taken delivery of the LI-8250, check the packaging list to be sure you received everything that you ordered.

LI-8250 Multiplexer

Part number LI-8250

The LI-8250 is the control unit for the system. It features a web interface for configuration from a Smart Phone, tablet, or computer with a web browser. Externally, it features a sealed connector panel for chambers or extension manifolds and one for gas analyzers and accessories.

The LI-8250 Multiplexer facilitates the connection of one or more gas analyzers with multiple chambers, providing the controller and data management for the system. Featuring embedded flux processing software, GPS, and internal storage, the LI-8250 Multiplexer can be used with LI-COR gas analyzers for real-time flux calculations or third-party gas analyzers for measure other gases.

By itself, the LI-8250 Multiplexer can connect with eight chambers. With one or more 8250-01 Extension Manifolds, the maximum number of chambers can be increased to 36. You configure and read data from the LI-8250 with the web browser of a Smart Phone, tablet, or computer using the LI-8250 built-in Wi-Fi or an Ethernet connection.

What's what

The LI-8250 has a main panel for gas analyzers and a port panel.

Main connection panel

The LI-8250 main connection panel features the power-in connector, three RJ-45 connectors for networked devices, such as trace gas analyzers, a USB connector for either the LI-870 or the 8250-02 Calibration Manifold, an auxiliary power-out connector for either the LI-870 or 8250-02 calibration manifold, the air in and air out for gas analyzers.

Power In: Connects to the power cable (8150-706) or the optional outdoor AC-to-DC power supply (8250-770).
Network Ports: Connects to trace gas analyzers, network, or cellular modem.
USB Port: Connects to the LI-870 or 8250-02 Calibration Manifold.
Power Out: Provides power to the LI-870 or the 8250-02 Calibration Manifold.
Air Out: To the gas analyzer air inlet or T-splitter if using multiple analyzers.
Air In: From the gas analyzer air outlet or T-splitter if using multiple analyzers.

Caution: The power output is 12 VDC with a center-positive pin, 2 A maximum. It powers either the LI-870 CO₂/H₂O Analyzer or the 8250-02 Calibration Manifold. Only use the included power cable (9982-010). Do not attempt to power any other devices with the PWR OUT connector. Drawing a current in excess of 2 A will open an internal circuit breaker, requiring a power cycle to reset.

Port connection panel

The LI-8250 has ports to connect with up to eight devices at a time, such as the 8250-01 Extension Manifold, the 8200-104 Opaque Long-Term Chamber, the 8200-104C Clear Long-Term Chamber, and user-built custom chambers.

Ports: The designated port number for the connected device. Each port has air in, air out, and a power/data connector.
Air In: Connects to the chamber or an extension manifold air outlet.
Air Out: Connects to the chamber or an extension manifold air inlet.
Power and Communication: Accepts the power and communication cable for extension manifolds or chambers.

Internal components

The internal components control the flow of air between analyzers, extension manifolds, and chambers.

Pump: Provides a steady flow of air through the system.
Port Valve Manifold: Controls the flow to and from each port.
System Valve Manifold: Controls the flow to and from the valve manifold and gas analyzers.
USB Ports: For connecting to an external Wi-Fi adapter or USB mass storage device.
Network Activity LEDs: Illuminated when connected; blinks when sending or receiving communication.
Ready LED: Steady light when the LI-8250 Multiplexer has finished booting up.
Power LED: Illuminates when the LI-8250 Multiplexer is receiving power.
Alternate Power Input: For connecting to the indoor AC-to-DC power supply (8250-772).

Included accessories and spares

The items listed are included with every LI-8250 Multiplexer.

Bare-leads power cable

Part number 8150-706

The bare-leads power cable is a 3-meter cable with bare wire leads that allows you to connect the LI-8250 Multiplexer to a user-supplied DC power source that reliably meets your power requirements. See Power requirements and consumption to estimate your total system power requirements.

Indoor AC-to-DC power supply

Part number 8250-772

The indoor AC-to-DC power supply provides a constant 24 VDC 80 W power using mains power. It is intended for indoor use only.

Ethernet cable

Part number 616-06116

This cable has two unsealed RJ-45 connectors and is used to connect the LI-8250 Multiplexer to a computer. Because the connectors are unsealed, this cable is not intended for field use. Ethernet cables may also be included in the optional cable assemblies, but these cables are sealed and strain-relieved for field use.

Spares kit

Part number 9982-072

This kit includes additional components and spare parts for the LI-8250 Multiplexer and 8250-01 Extension Manifold.

**Table 1‑1**. The spares kit for the LI-8250 and the 8250-01.
Description	Quantity	Part Number
Urethane Tubing (0.9 m)	1	222-00303
Balston Disposable Air Filter	1	300-01961
Hose Barb T-Fitting	2	300-02627
Hose Barb Replacement	2	300-17717
Vinyl Cap for Quick-Connect Plug	16	620-08298
Vinyl Cap for Quick-Connect Coupler	16	620-08299
Valve Manifold Air Inlet Filter	8	9981-123

Optional accessories

The following accessories are not included with the LI-8250 Multiplexer, but that are available from LI-COR for your soil gas flux system.

Outdoor AC-to-DC power supply

Part number 8250-770

When used with the LI-8250, the outdoor AC-to-DC power supply provides a constant 12 VDC 80 W power source. It is weather-resistant, O-ring sealed, and is designed for long-term outdoor deployment.

Sealed-to-standard Ethernet cables

Part numbers: 392-19109 or 392-19110

Sealed-to-standard Ethernet cables are available in lengths of 5 meters (part number 392-19109) or 25 meters (part number 392-19110). These cables have one sealed RJ-45 connector and one unsealed RJ-45 connector. They are used to connect the LI-8250 (sealed) to your site network (standard).

Cable and tube assembly for chambers and extension manifolds

Part number 9982-056

This cable assembly includes a 15-meter power and data cable with sealed connectors (part number 392-18852) and two 15-meter lengths of Bev-A-Line® tubing with quick-connect fittings. It provides power, communication, and gas flow between the LI-8250 Multiplexer, 8250-01 Extension Manifolds, and long-term chambers.

Chamber options

Depending on the system you ordered, you may have one or more of the 8200-104 Opaque Long-Term Chamber or 8200-104C Clear Long-Term Chamber. A patented pressure vent at the top of the chamber prevents pressure spikes when the chamber closes and maintains chamber pressure at ambient levels under calm and windy conditions. Chambers feature a built-in thermistor for a chamber air temperature measurement, which is used in flux calculations. Each soil chamber includes soil collars, a spares kit, and replacement gasket kit described below.

8200-104 Opaque Long-Term Chamber

Part number 8200-104

The 8200-104 Opaque Long-Term Chamber has a white enamel chamber bowl that rotates to and away from the soil collar. The 8200-104 is weatherized and intended to be left outdoors for extended periods of time to make automated measurements.

8200-104C Clear Long-Term Chamber

Part number 8200-104C

The 8200-104C Clear Long-Term Chamber has a clear chamber bowl that rotates to and away from the soil collar. The 8200-104C is weatherized and intended to be left outdoors for extended periods of time to make automated measurements. The clear chamber allows sunlight to reach plants in the collar, making this chamber suitable for measurement of net carbon exchange.

Soil collars

Part number 6581-044

Each chamber includes two soil collars. Soil collars are a short section of pipe that provides a seal between the chamber and the soil and should be installed at the measurement site at least 6 hours prior to measurements (although 24+ hours is better). Additional collars can be purchased from LI-COR or made in a shop if you have access to suitable materials (see Making your own soil collars).

Chamber spares kit

Part number 8100-613

Each chamber includes one chamber spares kit. This kit includes additional components and spare parts for each 8200-104/C Long-Term Chamber.

Description	Quantity	Part Number
T-handle nut	4	165-00140
Bumper	4	191-08069
Cable tie	9	218-08499
Urethane tubing (1.8 m)	1	222-00303
Cap plug	5	620-08297

Replacement gasket kit

Part number 8100-612

Each chamber includes one gasket kit that includes the components needed to replace the chamber gasket.

Description	Quantity	Part Number
Collar gasket	2	6581-060
Chamber gasket trim (1.8 m)	1	224-07606
Loctite adhesive	1	208-05786
6-32 x 3/8" screw	4	122-00009
4-40 x 3/8" screw	18	122-01578

LI-190R Quantum Sensor and leveling stake

Part number 190R-8200

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. The leveling stake is used to mount and level the LI-190R Quantum Sensor.

LI-200R Pyranometer and leveling stake

Part number 200R-8200

The LI-200R Pyranometer can be connected to the 8200-104/C Long-Term Chambers to measure solar radiation at the chamber to supplement your data. The leveling stake is used to mount and level the LI-200R Pyranometer.

Stevens HydraProbe

Part number 900-19016

A Stevens HydraProbe soil moisture, temperature, and electrical conductivity probe with a cable connector is available to connect to the 8200-104/C Long-Term Chambers. Ancillary data from the probe is captured alongside soil gas flux data.

SDI-12 sensor cable with flying leads

Part number 392-18518

Optional 2-meter cable with connector and flying leads to connect an SDI-12 sensor to the 8200-104/C Long-Term Chambers.

Sensor cable T-split fitting

Part number 310-18516

The sensor T-split fitting connects directly to a chamber port and serves as a junction for the connectors from two sensors, such as a light sensor and chamber thermistor, or multiple SDI-12 sensors to the 8200-104/C Long-Term Chambers.

Flask sampling kit

Part number 8250-660

The flask sampling kit is an accessory that modifies the LI-8250 to measure fluxes from discrete samples, such as soil samples, fruits, or small animals in user-supplied chambers, referred to as flasks. When used for flask sampling, the LI-8250 is compatible with 8250-01 Extension Manifolds, for up to 36 flasks. For gas measurements it is compatible with LI-78xx Trace Gas Analyzers and the 8250-02 Calibration Manifold, supporting measurements of CO₂, CH₄, N₂O, or Isotopes of CO₂.

See Support: LI-8250 Multiplexer for theory and operating information.

Description	Quantity	Part Number
Thermistor Input Module	1	9982-079
Purge pump	1	9982-077
Purge pump mount	1	9982-042
Bev-A-Line® tubing (15 m)	2	8150-250
M3-0.5 x 6 mm mounting screw	10	150-14477
M3-4.5 x 14 mm standoffs	4	161-18848
Washer	20	167-07256
Quick-connect bulkhead (sockets)	8	300-07126
Quick-connect bulkhead (pins)	8	300-07127
Barbed quick-connect plug (pins)	16	300-07124
Barbed quick-connect plug (sockets)	16	300-07125
Quick-connect plug	1	300-08151
Quick-connect fitting	2	300-08251
3/32" hex wrench	1	610-04290

Air Temperature Thermistor

Part number 9982-081

Preassembled, weatherized thermistors potted into a stainless-steel housing, fit to a sealed cable gland, and include a 15-m shielded cable. The cable gland mounts through a 12.5 mm diameter hole in materials up to 3 mm thick and is held in place by a nylon hex nut. The thermistor is compatible with the Thermistor Input Module and at least one should be used with flask configurations.

Custom chamber kit

Part number 8200-402

LI-COR offers a custom chamber kit that can be used to connect a custom chamber with the LI-8250 Multiplexer or 8250-01 Extension Manifold.

Description	Quantity	Part Number
Cable with connector bare leads	1	310-19090
Cable assembly	1	9982-056
Quick-connect bulkhead (sockets)	1	300-07126
Quick-connect bulkhead (pins)	1	300-07127
Seal washer	2	167-07256

Gas analyzer options

The LI-8250 Multiplexer is compatible with a variety of gas analyzers, including the LI-870 CO₂/H₂O Analyzer and LI-78xx Trace Gas Analyzers from LI-COR It is compatible with third-party gas analyzers as well. Below are brief descriptions of each of these analyzers and the components necessary to connect them to the multiplexer.

LI-870 CO₂/H₂O Analyzer

Part number LI-870

The LI-870 CO₂/H₂O Analyzer is a durable, weatherized gas analyzer that provides CO₂ data to the LI-8250 Multiplexer for soil CO₂ flux measurement.

The LI-870 measures CO₂ in air at concentrations from 0 to 20,000 ppm using non-dispersive infrared gas analysis. Water vapor measurements are used in corrections to report CO₂ dry mole fraction with high accuracy. Power to the LI-870 is supplied from the LI-8250 Multiplexer.

LI-870 and 8250-02 cable and tube assembly

Part number 9982-010

The cable assembly includes a 1.2-meter sealed USB-A-to-USB-B cable (part number 392-17654), a 1.2-meter IP68 sealed power cable (9982-008), and two pieces of Bev-a-line tubing with quick-connect fittings.

It provides power, communications, and gas flow between the LI-8250 Multiplexer and the LI-870 CO₂/H₂O Analyzer (see LI-870 cables and tubes). The same cable is used with the 8250-02 Calibration Manifold.

LI-78xx Trace Gas Analyzer

Part numbers
LI-7810,
LI-7815,
LI-7820, or LI-7825

LI-COR Trace Gas Analyzers are high-precision, high-stability, laser-based instruments that use Optical Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to measure gas concentrations in air.

LI-COR Trace Gas Analyzers provide data to the LI-8250 Multiplexer, which is used to compute flux results (see LI-78xx Trace Gas Analyzer cables and tubes). Up to three Trace Gas Analyzers can be attached to the LI-8250 at one time.

CO₂: LI-7810, LI-7815, LI-7825.
CH₄: LI-7810,
N₂O: LI-7820.
CO₂ Isotopologues: LI-7825.

LI-78xx cable and tube assembly

Part number 9982-011

To connect one LI-78xx Trace Gas Analyzer. The assembly includes a 2-meter Ethernet cable with two sealed RJ-45 connectors (part number 392-17793) and two pieces of Bev-a-line tubing with compression fittings. One is required for each trace gas analyzer.

T-split tube for multiple gas analyzers

Part number 9982-073

Pre-assembled T-split tubing for connecting multiple gas analyzers. The T-split tubing connects directly to the LI-8250 Multiplexer and serves as a junction for the air-in and air-out lines from the analyzers.

8250-01 Extension Manifold

Part number 8250-01

The multiplexer can support up to four extension manifolds, bringing the maximum number of chambers to 36. Each extension manifold includes a cable assembly (part number 9982-056; see Cable and tube assembly for chambers and extension manifolds), and a spares kit (part number 9982-072).

Because an extension manifold occupies a port, each 8250-01 Extension Manifold effectively adds another seven chambers to your system. The multiplexer can support four extension manifolds, which allows you use up to 36 chambers. Table 1‑2 shows how many extension manifolds are needed for each range of chambers.

**Table 1‑2**. Maximum number of chambers based on number of 8250-01 Extension Manifolds in the system.
Extension Manifolds	Chambers on Extension Manifold Ports	Chambers on Remaining Multiplexer Ports	Total Chambers
0	0	8	8
1	8	7	15
2	16	6	22
3	24	5	29
4	32	4	36