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Acclima-Digital True TDR-310H Soil Moisture Sensor (SDI-12)
Product Summary
The TDR-310H is the replacement to the former Acclima TDR-310S. It is fully compatible with the ‘310S but incorporates several improvements. Like the ‘310S it is an integrated time domain reflectometer that combines ultra-fast waveform generating and digitizing functions with a precision 5 ps resolution time base and highly sophisticated waveform digitizing and analyzing firmware that provides true time domain analysis of soil-propagated waveforms. Its form factor is designed for easy vertical installation in an augured hole using a 34 mm flat-bottomed auger. It mates with a 1” schedule 40 PVC pipe that acts as a handle in its installation to any desired depth. Its main improvements over the ‘310S are its faster rise time, its shaped incident wave, its lower power consumption and its very fast response time. Its interface is SDI-12 and is compatible with any data recorder that is compliant with SDI-12 version 1.4.
This digital TDR soil water content sensor (soil moisture sensor) is from the same family of the other Acclima True TDRs, however its rounded form factor allows it to easily attached to a (schedule 40) 1″ PCV pipe and/or be inserted into an access tube as small as 1.25″ (schedule 40 PVC) to be inserted into the soil at a specified depth.
The TDR-310H is the replacement to the former Acclima TDR310S soil moisture sensor. It is fully compatible with the ‘310S but incorporates several improvements. Like the ‘310S it is an integrated time domain reflectometer that combines ultra-fast waveform generating and digitizing functions with a precision 5 ps resolution time base and highly sophisticated waveform digitizing and analyzing firmware that provides true time domain analysis of soil-propagated waveforms.
Its form factor is designed for easy vertical installation in an augured hole using a 34 mm flat-bottomed auger. It mates with a 1” schedule 40 PVC pipe that acts as a handle in its installation to any desired depth. Its main improvements over the ‘310S are its faster rise time, its shaped incident wave, its lower power consumption and its very fast response time.
Its interface is SDI-12 and is compatible with any data recorder that is compliant with SDI-12 version 1.4.
Key Features
- SDI-12 Interface
- 3-element 10 cm stainless steel waveguide
- 34 mm round cross section with glue-on protrusion for mating with 1” schedule 40 PVC pipe
- 5 m 3-conductor waterproof cable
- Waterproof Epoxy-filled Housing
- 20% to 80% Incident Wave Rise Time: 150 ps
- Waveform Digitizing Resolution: 5 ps
Measurement Functions
- Volumetric Water Content: 0% to 100%
- Medium Permittivity: 1 to 80
- Medium Bulk Electrical Conductivity: 0 to 2000 µS/cm
- Medium Temperature: -40 to +60 degrees C
- Pore Water EC (Hilhorst Model): 0 to 55000 µS/cm
Battery Operation Performance
A major advantage of the TDR-310H over its predecessor TDR-310S is that its battery life has been increased 10 fold. This is due to lower current consumption and a faster read time.| Read Time (from issuance of read command until the return of data) | 0.25 seconds |
| Operating Voltage Range: | 3.5 to 15 volts dc |
| Idle Current Consumption: | < 10 µA |
| Idle Daily Energy Consumption @ 3.5 v: | 2 J/day |
| Current and Energy Consumption during Read: | current | power | energy* |
| 15v | 32 mA | 0.48 W | 0.12 J |
| 12v | 36 mA | 0.43 W | 0.11 J |
| 6v | 62 mA | 0.37 W | 0.09 J |
| 3.5v | 88 mA | 0.31 W | 0.08 J |
Permittivity Reporting
Permittivity is calculated directly from waveform propagation time and does not incorporate any voltage or current parameters. Hence the permittivity calculation is independent of soil electrical conductivity. This is the main advantage of true Time Domain Sensors over other types of sensors.| Reading Range: | 1 to 80 relative permittivity units |
| Reporting Resolution: | 0.1 relative permittivity units |
| Repeatability (RMS deviation): | 0.07 permittivity units |
| Coarse and medium textured soils: | ±1 relative permittivity units |
| Fine textured soils: | ±2 relative permittivity units |
Volumetric Water Content Reporting
VWC is calculated from permittivity using the Topp equation. Hence the accuracy of VWC reporting is that of the permittivity reporting and those further small errors imposed by the Topp equation. Note that the Topp equation is effective only to about 50% VWC. Acclima has replaced that segment of the equation with a linear function of propagation time beyond 50% VWC.| Reading Range: | 0 to 100% VWC |
| Reporting Resolution: | 0.1% VWC |
| Repeatability (RMS deviation): | 0.07% |
| Coarse and medium textured soils: | ±1 percentage point |
| Fine textured soils: | ±2.5 percentage points |
Bulk Electrical Conductivity Reporting
Bulk Electrical Conductivity of the soil is calculated from soil resistance measurements between the waveguide elements. Chromium oxide deposits on the waveguide elements becomes significant at high EC levels and the error correspondingly degrades in accuracy at those levels.| Reading Range: | 0 to 2000 µS/cm |
| Reporting Resolution: | 1 µS/cm |
| Repeatability (RMS deviation): | 3 µS/cm |
| 0 to 1000 µS/cm | 25 µS/cm |
| 1000 to 2000 µS/cm | ±2.5% |
Temperature Reporting
Soil Temperature is measured with a highly precise thermistor that is located about 2mm from one of the outer waveguide electrodes.| Reading Range: | -40C to +60C |
| Reporting Resolution: | 0.1 degree C |
| Repeatability (RMS deviation): | .01 % C |
| Reporting Accuracy: | ±0.25 degrees C |
Pore Water EC Reporting
This reading is calculated from permittivity and bulk EC using the Hilhorst model with an assumed soil type. Hence it is of limited accuracy and should be used only as a ball-park reading.
This Product does not include Tax and shipping costs. International shipping is subject to regulations and Import Taxation of Country of destination.
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