Delta-T Devices SM300 User manual

User Manual for the
SM300
Soil Moisture Sensor
Delta-T Devices Ltd
SM300-UM-1.2

Notices
Copyright
All parts of the SM300 design and documentation are the exclusive
right of Delta-T Devices and covered under copyright law.
Copyright © 2014 Delta-T Devices Ltd.
Patents
The SM300 is protected under international law by the following
patents:-
USA: Patent US7944220
Europe: Patent EP1836483
Australia: Patent AU2005315407
China: Patent CN101080631
EMC Compliance
See page 33.
Design changes
Delta-T Devices Ltd reserves the right to change the designs and
specifications of its products at any time without prior notice.
User Manual Version: 1.2
Delta-T Devices Ltd
130 Low Road, Burwell
Cambridge CB25 0EJ
UK
Tel: [phone]
Fax: [phone]
email: [e-mail]
web: www.delta-t.co.uk

SM300 User Manual 1.2

3
Contents
Introduction 5
Description 5
Features 5
Dimensions 6
Parts list 7
Care and Safety 8
How the SM300 works 9
Operation 10
Cable Connections 10
Installation 11
Logger connections and configuration 12
GP1 Logger 12
GP2 Logger Controller 13
DL6 Logger 14
DL2e Logger 15
Other data loggers 16
Logging Advice 16
Logger Grounding 17
HH2 Meter 20
Calibration 21
Soil calibration 21
Sensor calibration 24
Soil moisture reading 25
Troubleshooting 27
Technical Reference 29
Specifications 29
Volumetric water content 29
Temperature 29
Definitions 34
References 36

SM300 User Manual 1.2

4
Technical Support 37
Appendix 1 39
Soil-specific Calibration 39
Laboratory calibration for non-clay soils 40
Laboratory calibration for clay soils 43
Appendix 2: 46
The SM300 Temperature Sensor 46
SM300 Temperature Measurement 47
Effect of Temperature on Water Permittivity 49
Resistance to Temperature Lookup Table 50
Index 51

SM300 User Manual 1.2 Introduction

5
Introduction
Description
The SM300 measures soil moisture content and temperature.
Its sealed plastic body is attached to two sensing rods which
insert directly into the soil for taking readings.
A waterproof plug connects to a choice of signal cables.
Both extension cables and extension tubes can be used.
The soil moisture output signal is a differential analogue DC
voltage. This is converted to soil moisture by a data logger or
meter using the supplied general soil calibrations.
It can also be calibrated for specific soils.
Features
Soil moisture accurate to ± 2.5%
Soil temperature to ± 0.5°C over 0-40°C
Low salinity sensitivity
Excellent stability
Minimal soil disturbance
Easy installation at depth in augured holes
Waterproof connector to IP68
Rugged, weatherproof and can be buried.
Good electrical immunity
Choice of cabling system options
Cable connector, cylindrical profile and extension tube
design simplifies removal for servicing.
See also Specifications on page 29