TDT Data Sheet – Acclima ME

Acclima SDI-TDT Soil Moisture Sensor Data Sheet

September 4, 2021

Description

The Acclima Digital TDT® soil moisture sensor represents a revolutionary advance in the irrigation industry. It is the first soil moisture sensor to incorporate the accuracy of digitized Time Domain Transmissometry in a low-cost instrument providing highly accurate absolute readings of soil moisture under all conditions of temperature and soil chemistry where crops will grow. No other TDT sensor on the market matches its accuracy and stability. Independent test data from leading soil physicists verifies this extraordinary claim and are available upon request. This Digital TDT sensor incorporates a modified SDI interface capable of connecting directly to Acclima data loggers or any other third-party SDI version 1.4 compliant device. The Acclima modified SDI interface also is capable of auto-detection and address collision repair with Acclima data loggers.

No other TDT sensor on the market matches its accuracy and stability.

Features

Works in all soils

Highly stable under a wide range of soil conductivity and temperature

Range of 0 -100% volumetric water content

Made with durable inert materials

Very low-power, battery operable

SDI-12 version 1.4 compliant

Low cost

Physical Characteristics

Dimensions (without cable): 20 cm x 5.33 cm x 1.5 cm.

Weight (with 5-meter cable): 299 grams

Composition: Type 304 stainless steel, crystalline-epoxy

PVC (insulation) Cable: 3 conductor, 22 ga PVC sheath, 5 meters

Environmental Characteristics

Operating Temp Range: 1 ̊C to 50 ̊C for VWC (no ice), -20 ̊C to 50 ̊C for the other data

Storage Temp Range: 20 ̊C to 75 ̊C

Lightning & Surge Protection: 6 kV @ 3 kA, 8/50 µs

Operating Characteristics

Volumetric Water Content: 0 to 100%

Resolution: 06% VWC

Absolute VWC Accuracy: ±2% typical

VWC Soil EC Stability: ±1% of full scale 0 to 5 dS/m BEC

Temp Reporting Accuracy: ±2 ̊C from +1 ̊C to +50 ̊C

EC Reporting Accuracy: ±0.2 dS/m 0 to 5 dS/m BEC

Architectural Characteristics

Technology: Waveform Digitizing Time Domain Transmissometer

Effective Acquisition Bandwidth: 200 Giga-sample/second

Propagation Time Resolution: ps

Waveform Propagation Resolution: 5 mm in air, 0.16 mm in water

Waveguide Length: 30 cm

Permittivity to VWC Calculation: Modified Dielectric Mixing Model

Propagation Waveform Bandwidth: >2 GHz

Communications Characteristics

Communication Protocol: SDI-12 Revision 1.4

Maximum Cable Length: 60 meters

Power Characteristics

Operating Voltage Range: 6–15 VDC

Listening/Sleep Mode Current: 60 µA at 50 ̊C

Communications Current: 6 mA typical, 8 mA max

Read Moisture Comm Time: 425 ms total for each read cycle

Moisture Sense Current: 84 mA at 12VDC input, 98 mA at 8 VDC input, 110 mA at 6 VDC input

Moisture Sense Time: 450 ms each sensing operation

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