METER TEROS 21 Bedienungsanleitung
TEROS 21
i
TABLE OF CONTENTS
1. Introduction..............................................................................................1
2. Operation ................................................................................................... 2
2.1 Installation ................................................................................................2
2.2 Connecting................................................................................................. 3
3. System.........................................................................................................6
3.1 Specifications............................................................................................6
3.2 Components ..............................................................................................9
3.3 Theory........................................................................................................9
3.3.1 Water Potential Measurement .........................................................9
3.3.2 Measurement Range...................................................................... 10
3.3.3 Measurement Accuracy ................................................................. 12
3.3.4 Temperature Measurement............................................................ 13
3.4 Considerations......................................................................................... 13
3.4.1 Measuring in Frozen Soils.............................................................. 13
3.4.2 Measuring in High Salinity ............................................................. 14
3.4.3 Temperature Sensitivity................................................................. 14
4. Service....................................................................................................... 15
4.1 Calibration ............................................................................................... 15
4.2 Maintenance............................................................................................ 15
4.3 Troubleshooting....................................................................................... 16
4.4 Customer Support.................................................................................... 16
4.5 Terms and Conditions .............................................................................. 17
References .................................................................................................... 19
Index ................................................................................................................. 20
13755-03
11.10.2017
1
TEROS 21
1. INTRODUCTION
Thank you for purchasing the TEROS 21 Soil Water Potential Sensor from METER Group.
TEROS 21 was designed to be a maintenance-free matric potential sensor designed for long-
term, continuous field measurements. The TEROS 21 measures the dielectric permittivity of
a solid matrix to determine the water content of the solid matrix. The relationship between
water content and matric potential, known as the soil moisture characteristic curve, is used
to calculate the soil matric potential. This measurement approach, along with the calibration
process used in production, allows for accurate measurements of water potential.
Prior to use, verify the TEROS 21 arrived in good condition.
2
OPERATION
2. OPERATION
Please read all instructions before operating the TEROS 21 to ensure it performs to its
full potential.
SAFETY PRECAUTIONS
METER sensors are built to the highest standards, but misuse, improper protection, or
improper installation may damage the sensor and possibly void the manufacturer’s warranty.
Before integrating TEROS 21 into a system, follow the recommended installation instructions
and have the proper protections in place to safeguard sensors fromdamage.
2.1 INSTALLATION
Follow the steps listed in Table 1 to set up the sensor. It is critical that the sensor has good
hydraulic contact with the soil to make accurate measurements.
Table 1 Installation
Tools Needed
Auger or shovel
Knife (if installing in shallow depth)
Water (for packing soil or making slurry)
Preparation
Check Sensor Functionality
Plug the sensor into the logger (Section 2.2) to make sure the sensor
isfunctional.
Field Installation
Create Hole
Auger or trench a hole to the desired sensor depth.
Pack Sensor
Moisten native soil and pack it rmly around the entire sensor discs. Ensure
the soil is in contact with all surfaces of the ceramic.
NOTE: Sandy soils may not adhere to the sensor even when wet. If so, place the sensor at
the bottom of the hole and carefully pack the soil around the sensor. Be sure to pack the
soil firmly around ceramic surfaces.
3
TEROS 21
Table 1 Installation (continued)
Field Installation
(continued)
Install Sensor
For shallow installation (less than ~30 cm), use a knife to remove a small sliver
of soil. Insert packed sensor into the channel.
For deep installation (greater than ~30 cm), use the native soil to make a slurry
with water. Lower sensor into the hole and ll with the slurry.
NOTE: Soils with high shrink-swell potential may pull away from the sensor as they dry
and disrupt measurements.
NOTE: Do not install the sensor with the body exposed above ground.
Connect to Logger
Leave at least 15 cm (6 in) of sensor cable beneath the soil before bringing the
cable to the surface. At least 10 cm (4 in) of cable should exit the sensor body
in a straight line before bending the cable.
Plug the sensor into the logger.
Use the data logger to make sure the sensor is reading properly.
Return soil to the hole, packing the soil back to its native bulk density.
2.2 CONNECTING
The TEROS 21 sensors work best with METER data loggers or ProCheck handheld readers.
1. Check data logger software and firmware versions to ensure they support
TEROS21 sensors (http://www.metergroup.com/teros21-support/).
Plug the stereo plug connector directly into one of the sensor ports.
2. Congure the logger port for TEROS 21 using the appropriate logger application.
The TEROS 21 sensors have a 5-m cable. Customers may purchase custom cable lengths
for an additional per-meter fee. If the cable needs to be extended, ensure to adequately
waterproof the cable splices to prevent a major failure point. Read Wire splicing and sealing
technique for soil moisture sensors for more information.
The sensor uses a 3.5-mm stereo plug connector (Figure1). Customers may purchase the
sensor with stripped and tinned wires (pigtail) for terminal connections for third-party data
loggers (Figure2). Refer to the individual third-party logger manual for details on wiring.
NOTE: The acceptable range of power voltages is from 3.9 to 15.0 VDC, with 12 VDC being the optimal voltage.
Ground
Data
Power
3.5-mm stereo plug connector
4
OPERATION
Ground (bare)
Data (orange)
Power (brown)
Pigtail wiring
NOTE:Sensors manufactured as MPS-6 use white wire for power and red wire for data output.
TEROS 21 sensors communicate using two different methods: serial (TTL) and SDI-12.
Please refer to the complete TEROS 21 Integrator Guide for more detailed explanations
andinstructions.
There are two options to connect a sensor with the standard stereo plug to a non-METER
data logger.
Option 1
1. Clip the plug off the sensor cable.
2. Strip and tin the wires.
3. Connect the wires directly into the data logger.
This will create a direct connection with no chance of the sensor becoming unplugged;
however, the sensor cannot be easily used in the future with a METER readout unit or
datalogger.
Option 2
Obtain an adapter cable from METER.
The adapter cable has a 3.5-mm stereo plug connector for connecting to the sensor on one
end and three wires for connecting to a data logger (a stereo-to-pigtail adapter) on the other
end. The stripped and tinned adapter cable wires have the same termination as seen in
Figure2; the brown wire is power, orange is output, and the bare wire is ground.
Because TEROS 21 sensors use digital communication, they require special considerations
when connecting to an SDI-12 data logger. Read SDI-12 example programs to view sample
Campbell Scientific programs.
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TEROS 21
The SDI-12 protocol requires that all sensors have a unique address. TEROS 21 sensors
factory default is an SDI-12 address of 0. To add more than one SDI-12 sensor to a bus, the
sensor address must be changed as described below:
1. Using a ProCheck connected to the sensor, press the Menu button to bring up the
CONFIGmenu.
NOTE: If the ProCheck does not have this option, please upgrade its firmware to the latest version from the METER
Legacy Handheld Devices webpage.
2. Scroll down to SDI-12 Address. Press Enter.
3. Press the UP or DOWN arrows until the desired address is highlighted.
Address options include 0...9, A…Z, and a…z.
4. Press Enter.
Detailed information can also be found in the application note Setting SDI-12 addresses on
METER digital sensors using Campbell Scientific data loggers and LoggerNet.
When using the sensor as part of an SDI-12 bus, excite the sensors continuously to avoid
issues with initial sensor startup interfering with the SDI-12 communications.
SDI-12 communication can convey multiple parameters from a single function call. In the
data stream, TEROS 21 reports (1) the sensor address, (2) the water potential (in kilopascals),
and (3) the temperature (in Celsius).
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SYSTEM
3. SYSTEM
This section reviews the components and functionality of the TEROS 21 sensor.
3.1 SPECIFICATIONS
Water Potential
Range: −9 to −100,000 kPa (1.96 to 6.01 pF)
Resolution: 0.1 kPa
Accuracy: ±(10% of reading + 2 kPa) from −9 to −100 kPa
Temperature
Range: −40 to 60 °C
Resolution: 0.1 °C
Accuracy: ±1 °C
Operating Temperature
−40 to 60 °C (0%–100% RH)
No water potential measurement <0 °C
NOTE: Sensors may be used at higher temperatures under certain conditions; contact Customer Support
Power Requirements
3.9 to 15.0 VDC, 0.03 mA quiescent, 10 mA max during 150-ms measurement
Dimensions
9.6 cm × 3.5 cm × 1.5 cm
Sensor Diameter
3.2 cm
Dielectric Measurement Frequency
70 MHz
Measurement Time
150 ms
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