Delta-T SM150T Quick Start Manual
Delta-T SM150T is a soil moisture sensor that can be used for manual readings with or without memory, and automatic readings with external data loggers. The sensor can be installed at various depths with optional accessories. It is compatible with HH150, HH2 meters, and various data loggers like GP2, GP1, DL6, and DL2e. The sensor provides accurate soil moisture measurements and can be used for various applications such as irrigation management, soil moisture monitoring, and environmental research.
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SM150T
Soil Moisture Sensor
Quick Start Guide
Version 4.0
Delta-T Devices Ltd
SM150T overview
Manual readings
Manual readings with memory
3 HH150
4 HH2
Automatic readings with memory
5 Data
Loggers
1
Cables
© 2017 Delta-T Devices Ltd
2 Installation
Page 2
1
Cables and Accessories
SM150T
soil moisture sensor
SM150T + HH150 Kit
SM150T + HH2 Kit
includes SMSC/d-HH2 cable
HH150 includes 1m cable,
Connects to SM150T
SMCS/d-HH2 0.9m cable
Connects SM150T to HH2
SMSC/lw-05
5m cable
200mm flying leads
Connect to data logger
L
ogger extension cables
EXT/5W-05
5m
EXT/5W-10
10m
EXT/5W-25
25m
Extension tubes
ML/EX50
50cm
ML/EX100
100cm
SM-AUG-100 Spiral Auger 1.2m
Logger Extension cables can be joined up to a maximum length of 100m.
Align connectors carefully before pushing parts together.
Screw together firmly to ensure the connection is water-tight.
Note: HH150 and HH2 meters do not read SM150T temperature.
© 2017 Delta-T Devices Ltd Page 3
2
Installation
Surface installation and spot measurements
◼
Clear away any stones.
Pre-form holes in very hard soils before insertion.
◼
Push the SM150T into the soil until the rods are fully inserted. Ensure good soil contact.
◼
If you feel strong resistance when inserting the
SM150T, you have probably hit a stone. Stop, and re-insert at a new location.
Note: The SM150T is not suitable for soil surface temperature measurements. For soil temperature near the surface dig a trench and install horizontally as shown below.
Cover both SM150T and the first 30cm of cable with at least 5cm of soil.
Installing at depth
◼
Auger a 45mm diameter hole. ~10° to vertical is recommended.
◼
Fit an extension tube to the SM150T
– remember to pass the cable through the extension tube and fit the connector first.
◼
Push the SM150T into the soil until rods are fully inserted. Ensure good soil contact.
Alternatively
◼
Dig a trench, and install horizontally.
Note: Extension tubes are available for installing the
SM150T in an augered hole.
© 2017 Delta-T Devices Ltd Page 4
3
HH150 Meter
Turn on, take and display reading
Turn on, show current setting
Read
Mineral
32.2%vol
Read
Mineral
34.3%vol
OFF
Mineral
▼
Peat mix
▼
Coir
▼
Min.wool
▼
Perlite
▼
Volts
▼
OFF
Read
◼
Connect the SM150T to the HH150 meter.
◼
With the meter OFF, press the right off – menu button. This wakes and allows you to set the meter to display readings - either as % volumetric water content of
Mineral, Peat mix, Coir, Min. wool, Perlite , or show the sensor output in Volts.
◼
Press the left on
– read button to take a reading.
Repeat as required. You may wish to write down the readings.
The meter will sleep after 30 seconds.
The battery should last for about 10,000 readings.
HH150 does not read
SM150T temperature
How to Change Battery
Place face down
& remove screws
P RESS DOWN
Holding the cable down against the front cover - remove the back
Fit new batteries
Only use good quality alkaline batteries
Replace back cover
© 2017 Delta-T Devices Ltd Page 5
4
HH2 Meter
Note the HH2 does not read the temperature sensor.
Use version 2.8 or later of both the PC software HH2Read and the HH2 firmware (see footnote)
◼
Connect the SM150T to the HH2 meter.
◼
Press Esc to turn the meter on, and if necessary press again until the HH2 displays the start-up screen.
◼
Set the meter to read from an SM150T:
►
Press Set and scroll down to the Device option.
►
Press Set again and scroll down to select
SM150T.
►
Press Set to confirm this choice.
Device:
SM150T
◼
Make sure the HH2 is correctly configured for your soil type:
►
At the start-up screen, press Set and scroll down to the Soil Type option.
►
Press Set again and scroll down to the appropriate soil type (use Mineral for sand, silt or clay soils or Organic for peaty soils)
►
Press Set to confirm this choice.
Soil Type:
Mineral
◼
Choose the units you want for displaying readings:
►
At the start-up screen, press Set and scroll down to the
Display
option.
►
Press Set again and scroll down to select units.
►
Press Set to confirm this choice.
◼
Press Read to take a reading.
SM150T Store?
20.3%vol
◼
Press Store to save or Esc to discard the reading.
◼
Remove the SM150T from the soil and move to a new location...
◼
If you have saved data, connect your HH2 to a PC and run HH2Read to retrieve the readings.
Note: For an upgrade contact Delta-T.
See also: HH2 User Manual
© 2017 Delta-T Devices Ltd Page 6
5
Data Loggers
GP2
◼
6 SM150Ts can connect to a GP2
12 can be connected if not using the temperature sensors
If using more than 9 you need expansion lid GP2-G5-LID .
These details illustrate connection to Channels 1 and 2:
SM150T wiring Colour GP2 terminal
Power 0V brown CH1 (PGND)
Power V+ white CH1 (PWR)
Soil Moisture Signal HI blue CH1 (+)
Soil Moisture Signal LO black CH1 (-)
Cable shield green CH1 (PGND)
Thermopile HI grey
CH2(+) and CH2(-)
Fit wire link
Configure channel 1 as type SM150T and channel 2 as SM150T Temperature .
See also DeltaLINK * software sensor Info Panel and Help or the GP2 User Manual.
GP1
◼
2 SM150Ts can connect to each GP1. Each SM150T is wired as a differential, powered sensor..
Channel 1 and 3 wiring:
SM150 wiring Colour GP1 terminal
Power 0V
Power V+
Signal HI
Signal LO brown CH1 (GND) white CH1 (PWR) blue black
CH1 (+)
CH1 (-)
Cable shield green CH1 (GND)
Temperature+ grey Temp3 (IN)
◼
Using DeltaLINK * logger software (version 3.6* or later) configure channel 1 as
SM150T(soil moisture) and channel 2 as SM150T(temperature) .
See also GP1 Quick Start Guide and DeltaLINK Help .
* Download the latest version of the DeltaLINK logger software, v3.6 or later, from www.deltat.co.uk
or from our Software and Manuals DVD
© 2017 Delta-T Devices Ltd Page 7
DL6
◼
Up to 6 SM150Ts can connect to a DL6 logger but only one of the integrated temperature sensors can be connected.
◼
Each is wired as a differential, powered sensor.
These details illustrate connection to channel 6 and 7:
SM150T wiring Colour DL6 terminal
Power 0V
Power V+
Signal HI
Signal LO
Temperature + brown white blue black grey
0V
V+
IN+
IN-
RES IN+
Cable shield green
◼
In DeltaLINK configure channel 1 - 6 as Moisture Probe SM150T and channel 7 as SM150T Temperature .
See also the DL6 Quick Start Guide and the DeltaLINK onlin Help.
* Download the latest version (v3.6 or later) of the DeltaLINK logger software from www.delta-t.co.uk
or from our Softaware and Manuals DVD.
DL2e
◼
Up to 30 SM150Ts may be connected (or 60 if not reading the temperature).
◼
Each soil moisture sensor is connected as a differential, powered sensor.
This example uses channels 57 and 58 with a LAC1 input card configured in 15-channel mode, and warm-up channel 63.
SM150T wiring Colour DL2e terminal
Power 0V
Power V+
Signal HI
Signal LO brown CH62- or 61- white blue black
CH63 NO
CH58+
CH58-
Cable shield green CH61- or 62-
Temperature + grey CH57+ and CH57-
◼
Configure the DL2e logger channels by selecting the appropriate SM150T sensor types from the LS2Win sensor library. Use Ls2Win version 1.0 SR10 or later*.
See also the DL2e User Manual or LS2Win Help .
* Download the latest version of Ls2Win logger PC software from www.delta-t.co.uk
or from our Software and Manuals DVD.
© 2017 Delta-T Devices Ltd Page 8
6
How to calculate soil moisture
◼
Take a reading with the SM150T either
◼
Convert the reading to
using equation 1 or the linearisation table below.
◼
Then convert
to soil moisture,
, using the soil calibration values ( a
0
, a
1
).
or
◼
Convert directly for mineral or organic soils using equations 2 or 3
Example
V = 0.294 volts
= 3.52
= 22.9% for mineral soil
= 22.9%
Conversion to
Polynomial (for use over the full range of SM150T readings)
√𝜖 = 1.0 + 14.4396𝑉 − 31.2587𝑉
2 + 49.0575𝑉 3 − 36.5575𝑉 4 + 10.7117𝑉 5 ……… .(1) where V is the SM150T output in volts
Linearisation table (for use over the full range of SM150T readings)
V
V
V
V
V
0.000 1.000 0.300 3.576 0.600 5.101 0.900 6.778 1.200 8.924
0.075 1.942 0.375 3.964 0.675 5.503 0.975 7.232 1.275 9.743
0.150 2.620 0.450 4.337 0.750 5.917 1.050 7.720 1.350 10.808
0.225 3.144 0.525 4.713 0.825 6.342 1.125 8.270 1.425 12.242
Conversion from
to Soil Moisture
a
0 a
1
◼
Soil moisture 𝜃 = (√𝜀 − 𝑎
0
)/𝑎
1
◼
Use these generalised soil calibration values for
Mineral
Organic
1.6
1.3
8.4
7.7 mineral and organic soil types, or carry out a soilPeat mix 1.16 7.09 specific calibration to derive your own values
Coir 1.16 7.41
See SM150T User Manual .
Min. wool 1.04 7.58
◼
Multiply x100 to convert soil moisture from
Perlite m 3 .m
-3 to % volumetric.
Direct conversion for Mineral and Organic soils
1.06 6.53 𝜽 𝒎𝒊𝒏𝒆𝒓𝒂𝒍
= −0.0714 + 1.7190𝑉 − 3.7213𝑉 2 + 5.8402𝑉 3 𝜽 𝒐𝒓𝒈𝒂𝒏𝒊𝒄
= −0.0390 + 1.8753𝑉 − 4.0596𝑉 2 + 6.3711𝑉 3
− 4.3521𝑉 4 + 1.2752𝑉 5 … (2)
− 4.7477𝑉 4 + 1.3911𝑉 5 … (3)
© 2017 Delta-T Devices Ltd Page 9
7
Check Sensor is working
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
Air reading
◼
Hold the SM150T in air and away from other objects and take a reading using an
HH150 meter, or an HH2 meter or voltmeter or a logger with no more than 5m of cable. In air the reading should be 0 ±4mV
(Note: the HH150 reports under-range if the reading is less than zero )
Warning: Do not touch the pins
Try not to touch the pins. A typical electrostatic discharge from your body can create a temporary offset in sensor readings for up to one hour.
Water reading
◼
Measure the output in voltage.
In the UK the sensor will typically read about 1.5 volts in tap water (because the salinity is typically 50mS.m-1).
The “water reading” you get will depend on the salinity of your local water.
Note: HH150 meter indicates “TOO WET” above 1.5V or 85% vol .
SM150 fully immersed in water - as read by HH150 and HH2 meters
"TOO WET"
Volts
% vol (mineral)
%vol (organic)
100 200 300 400
Conductivity EC p
(mS.m
-1 )
500
100.00%
90.00%
80.00%
70.00%
60.00%
50.00%
40.00%
30.00%
20.00%
10.00%
600
0.00%
Soil moisture readings are not correct when no soil is present i.e. at
100% vol.
SM150T tables and polynomial constants are optimised at 220 mS.m
-1 for soil moisture values below 70%vol
Graph: showing the effect of salinity on SM150T sensor output when fully immersed in water with no soil present.
© 2017 Delta-T Devices Ltd Page 10
8
Specifications
(for full specification see SM150T User Manual)
Volumetric Water Content
Accuracy
3.0% vol over 0 to 70 % vol and 0-60°C
Measurement range
Salinity error
0 to 100% vol but less accurate above 70%vol**
5% vol over 100 to 1000 mS.m
-1 and 0-60% vol
Conductivity response
Temperature sensitivity
Sampling volume
Output signal
Output compatible with
Temperature
Sensor accuracy
See SM150T User Manual
See SM150T User Manual
See SM150T User Manual
0-1 V differential
0 to 60% nominal
HH150, HH2, GP1, GP2, DL6, DL2e
SM150T must be fully buried to accurately measure soil temperature
± 0.5°C over 0-40°C * not including logger or cabling error
Output
Output compatible with
Cabling error contribution (to temperature reading)
Maximum cable length
Power requirement
Operating range
Environment
Sample volume
Dimensions
Weight
Resistance: 5.8kΩ to 28kΩ*
GP1, GP2, DL6* DL2e
0°C for GP1, GP2 & DL6 (any cable length)
0°C for DL2e (with 5m cable).*
100m (GP1, GP2 & DL6 data loggers) 100m
(DL2e: water content measurement) 25m (DL2e: temperature measurement)
5-14VDC, 18mA for 1s
-20 to +60°C
IP68***
55 x 70 mm diameter
143 x 40 mm diameter
77 gm (without cable)
HH150 meter
Accuracy
Resolution
Battery / life/standby life
Environmental
Compliance does not read SM150T temperature
±7.5mV (negligible effect on SM150 accuracy)
0.1% of volumetric reading or 1mV
2xGP alkaline AAA/ 10000 readings/1 year
Non condensing
CE, FCC & ROHS
* Note: See full specification in SM150T User Manual
** In water (no soil present) the reading may not be 100% vol.
It depends on a0 and a1 but can still be used as a quick check that the unit is working.
*** With Delta-T supplied cables
© 2017 Delta-T Devices Ltd Page 11
Field of sensitivity
SM150T Error close to wall of plant pot.
live pin nearest to pot wall
1%
0%
-1%
-2%
-3%
-4%
-5%
-6%
0 5 10 15 20 25
Gap between SM150 body and wall of pot (mm)
30 35
This graph shows the effect of being too close to the wall of a plant pot and gives a partial indication of the shape of the field of sensitivity around the pins
9
Care and Safety
40
◼
Do not touch the rods or expose them to other sources of static damage, particularly when powered up.
◼
Keep the SM150T in its protective tube when not in use.
◼
Ensure that the connectors are clean, undamaged and properly aligned before pushing the parts together. Screw together firmly for water-tight seal.
◼
Do not pull the sensor out of the soil by its cable.
◼
If you feel strong resistance when inserting into soil, it is likely you have encountered a stone. Stop pushing and re-insert at a new location.
Delta-T Devices Ltd
130 Low Road
Burwell
Cambridge CB25 0EJ
England (UK)
Tel : +44 1638 742922
Fax : +44 1638 743155
E-mail : [email protected]
Web : www.delta-t.co.uk

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