Tekbox TBSLWS1 User manual

V1.2
TBSLWS1
SDI-12 Leaf Wetness Sensor
© 2014 Tekbox Digital Solutions
50/11 Truong Son, F2 | Q. Tan Binh | Ho Chi Minh City | Tel [phone] | E-mail [email protected]| www.tekbox.net
Mimics the wetness state of a real leaf
Measurement range: 0 %to 100%
Measurement response: 1 sec
SDI-12 Standard V1.3
Plug and Play
6 - 16V supply voltage
Less than 40µA idle current
Operating Temperature Range:
- 40°C … + 80°C

TBSLWS1 SDI-12 Leaf Wetness Sensor

V1.2
TBSLWS1 SDI-12 Leaf Wetness Sensor
Contents
1INTRODUCTION
7APPLICATION EXAMPLES
8MECHANICAL DIMENSIONS
11 ORDERING INFORMATION
12 HISTORY
Tables
Table 1 –Cable Connection
Table 2 –Standard SDI-12 commands
Table 3 –Extended SDI-12 Commands
Table 4 –Ordering Information
Table 5 –History
Figures
Figure 1 –TBSLWS1 measurement output during rainfall and consecutive drying phase
Figure 2 –TBSLWS1 and other sensors with SDI-12 interface connected to TBS03 SDI-12 to USB converter;
setup for controlling / testing sensors and for PC based data recording
Figure 3 –TBSLWS1 and other sensors with SDI-12 interface connected to Remote Telemetry Unit or Data
Recorder

V1.2
TBSLWS1 SDI-12 Leaf Wetness Sensor
1 Introduction
The graph below shows the output of the TBSLWS1 leaf wetness sensor. When the sensor is dry, the output
value delivered upon a SDI-12 measurement command is 0% or very close to zero. When rain drops hit the
surface of the sensor, the measurement response will be anywhere between 0% and 100%, depending on how
much of the sensor area is covered with water drops. Typically the result will show some fluctuation during
rainfall. Raindrops on the sensor surface merge to bigger drops until they reach a size where gravity exceeds
surface adhesion and the drop flows from the sloped surface. Similarly, wind gusts can blow drops from the
surface and change the state of wetness. Consequently there is some fluctuation in the amount of raindrops on
the sensor surface during rainfall.
During the drying phase, the measurement curve is much smoother, as there is much less dynamics on the
sensor surface compared to the phase of rainfall.
Figure 1 –TBSLWS1 measurement output during rainfall and consecutive drying phase
A measurement result of 100% is equivalent to the complete sensor surface submerged in water and a value of
0% is equivalent to a completely dry surface. The sensor comes factory calibrated. Upon requirement, the user
can carry out an air/water calibration using extended SDI-12 commands.
The TBSLWS1 outputs the measured leaf wetness in %:
Measurement commands:
aM! aMC! aC! aCC! Leaf wetness [%]
aM1! aMC1! aC1! aCC1! Leaf wetness [%] and board temperature [°C]
aM2! aMC2! aC2! aCC2! Board temperature [°C]

V1.2
TBSLWS1 SDI-12 Leaf Wetness Sensor
The default measurement unit for board temperature is degree Celsius, however using an extended SDI-12
command, the result can be changed to Fahrenheit
Extended SDI-12 commands:
aXCA! Air calibration factory calibrated
aXCW! Water calibration factory calibrated
The leaf wetness sensor is factory calibrated and can be installed right out of the box. Refer to chapter 4 for
details.
aXCT,stt.tt! temperature calibration factory calibrated
where s: sign
where tt.tt: ambient temperature measured with a reference thermometer
The temperature calibration is carried out in production; in case of a re-calibration, allow the sensor half an hour
to settle to room temperature
aXSTUu! set temperature unit; u= C for °C; u=F for °F
aXGTU! query temperature unit
Use the above command to configure the temperature unit; [°C] is the default setting
Measurement range: 0 to 100%
Measurement principle: capacitive measurement, PLL
Measurement response: 1 sec
SDI-12 Standard V1.3
6 - 16V supply voltage
Operating Temperature Range: - 40°C … + 80°C
Current consumption: active 8mA (for 1 second); idle 30µA
Standard cable length: 3m; any other length upon requirement
The TBSLWS1 comes factory calibrated and does not need any user calibration.
The TBSLWS1 is air / water calibrated. For air calibration, the dry sensor is placed in a way that its surface is not
touched by any object. Then issue the air calibration command. For water calibration, the complete sensor surface
is submerged in water and then the calibration command is issued.
If a higher sensitivity is required, the water calibration can be carried out with the sensor surface not completely
submerged in water, e.g. just half of the surface dipped into water when calibrating.

V1.2
TBSLWS1 SDI-12 Leaf Wetness Sensor
The TBSLWS1 is compatible with any data logger or remote telemetry unit with SDI-12 interface. Refer to the data
logger or RTU manual and to chapter 7 and 8 of this datasheet. Chapter 7 refers to the electrical installation;
chapter 8 refers to the mechanical drawing.
The TBSLWS shall be mounted at an angle to mimic a leaf.
SDI-12 is a standard for interfacing data recorders with microprocessor-based sensors. SDI-12 stands for
serial/digital interface at 1200 baud. It can connect multiple sensors with a single data recorder on one cable. It
supports up to 60 meter cable between a sensor and a data logger.
The SDI-12 standard is prepared by
SDI-12 Support Group
(Technical Committee)
165 East 500 South
River Heights, Utah
435-752-4200
435-752-1691 (FAX)
http://www.sdi-12.org
The latest standard is version V1.3 which dates from July 18th, 2005. The standard is available on the website of
the SDI-12 Support Group.
More information on SDI-12 is presented in chapter 3.

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TBSLWS1 SDI-12 Leaf Wetness Sensor
7 Application Examples
Figure 2 –TBSLWS1 and other sensors with SDI-12 interface connected to TBS03 SDI-12 to USB converter; setup for
controlling / testing sensors and for PC based data recording
Figure 3 –TBSLWS1 and other sensors with SDI-12 interface connected to Remote Telemetry Unit or Data Recorder

V1.2
TBSLWS1 SDI-12 Leaf Wetness Sensor
8 Mechanical Dimensions
Cable Color
Signal Assignment
Red
SDI-12 Power
Blue
SDI-12 Data
Black
GND / Shield
Table 1 –Cable Connection

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TBSLWS1 SDI-12 Leaf Wetness Sensor
Following standard SDI-12 commands are supported by the TBSLWS1:
Command
Description
Response
a!
Acknowledge Active
a<CR><LF>
aI!
Send Identification
013TEKBOXVNTBSAB21.0000005xxxxx<CR><LF>
With xxxxx representing the serial number
aAb!
Change Address
b<CR><LF>
Changing the sensor address from a to b
?!
Address Query
a<CR><LF>
aM!
Start Measurement
Measures leaf wetness [%]
attt1<CR><LF>
Delay (ttt = 001) in seconds and number of values (1)
aM1!
Additional Measurement
Measures leaf wetness [%] and board
temperature [°C/F]
attt1<CR><LF>
Delay (ttt = 001) in seconds and number of values (2)
aM2!
Additional Measurement
Measures board temperature [°C/F]
attt1<CR><LF>
Delay (ttt = 001) in seconds and number of values (1)
aMC!
Start Measurement and request CRC
Measures leaf wetness [%] and calculates
CRC
attt1<CR><LF>
Delay (ttt = 001) in seconds and number of values (1)
aMC1!
Additional Measurement and request
CRC
Measures leaf wetness [%] and board
temperature [°C/F] and calculates CRC
attt1<CR><LF>
Delay (ttt = 001) in seconds and number of values (1)
aMC2!
Additional Measurement and request
CRC
Measures board temperature [°C/F] and
calculates CRC
attt1<CR><LF>
Delay (ttt = 001) in seconds and number of values (1)
aC!
Start Concurrent Measurement
Measures leaf wetness [%]
attt1<CR><LF>
Delay (ttt) in seconds and number of values (4)
aC1!
Start Concurrent Measurement
Measures leaf wetness [%] and board
temperature [°C/F]
attt1<CR><LF>
Delay (ttt) in seconds and number of values (4)
aC2!
Start Concurrent Measurement
Measures board temperature [°C/F]
attt1<CR><LF>
Delay (ttt) in seconds and number of values (4)
aCC!
Start Concurrent Measurement and
request CRC
Measures leaf wetness [%] and calculates
CRC
attt1<CR><LF>
Delay (ttt) in seconds and number of values (4)
aCC1!
Start Concurrent Measurement and
request CRC
Measures leaf wetness [%] and board
temperature [°C/F] and calculates CRC
attt1<CR><LF>
Delay (ttt) in seconds and number of values (4)

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TBSLWS1 SDI-12 Leaf Wetness Sensor
aCC2!
Start Concurrent Measurement and
request CRC
Measures board temperature [°C/F] and
calculates CRC
attt1<CR><LF>
Delay (ttt) in seconds and number of values (4)
aD0!
Get Measurement Result(s)
Upon issuing the aD0! Command, the TBSLWS1 will send
the measurement results. The response format depends
on the measurement command issued before.
aV!
Start Verification
a0000<CR><LF>
Not supported
aRn!
aRCn!
Continuous Measurement
Continuous Measurement + CRC
a<CR><LF>
Not supported
Table 2 –Standard SDI-12 commands
Following extended SDI-12 commands are supported by the TBSLWS1:
Command
Description
Response
aXCA!
Air calibration
Place the dry sensor in air and issue the air calibration command. Do not touch the surface,
while calibrating.
aX_ok<CR><LF>
aXCW!
Water calibration
Submerge the sensor surface into a glass filled with water and issue the water calibration
command.
aX_ok<CR><LF>
aXCT,stt.tt
Temperature calibration
s: sign
tt.tt: ambient temperature measured with a reference thermometer
aX_ok<CR><LF>
aXSTUu!
Set temperature unit
u = F for [°C], u = f for [°F]
aX_ok<CR><LF>
aXGTU!
Query temperature unit
au<CR><LF>
Table 3 –Extended SDI-12 Commands
11 Ordering Information
Part Number
Description
TBSLWS1
TBSLWS1, Leaf wetness sensor with 3m cable
Please mention in your order, if you require a different cable length
Table 4 –Ordering Information

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TBSLWS1 SDI-12 Leaf Wetness Sensor
12 History
Version
Date
Author
Changes
V1.0
24.06.2014
Mayerhofer
Creation of the document
V1.1
17.10.2014
Mayerhofer
Correction of temperature calibration command: sign
added
V1.2
18.02.2015
Mayerhofer
Corrections
Table 5 –History