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Vegetronix Soil Temperature Sensor Probes

Buy THERM200 Now

The THERM200 is a soil temperature probe, which has a temperature span from -40°C to 85°C.  It outputs a voltage linearly proportional to the temperature, so no complex equations are required, to calculate the temperature from voltage.  It is highly accurate with 0.125°C of resolution.

The sensor has a simple 3 wire interface: ground, power, and output,  and  is powered from 3.6V to 20VDC, and outputs a voltage 0 to 3V. Where 0 represents -40°C and 3V represents 85°.

The probes can be buried, or inserted into pots. Since the blade is so narrow, it can easily be inserted into potted plants.    

The temperature sensor can be used with our soil moisture sensors, and together they can be used to detect the presence of ice.  

The THERM200 is compatible with our data Loggers, or  any other third-party data logger. 

Thermistor based temperature sensors, are typically inaccurate, and use the complex Steinhart-Hart equation which contains complex calculations such as logarithmic and third order terms, which are difficult for microcontrollers to compute. 

Once you've tried the THERM200, you'll never want to use a thermistor based sensor again.  


Soil Temperature Sensor
THERM200 - Soil Temperature Sensor Probe


Soil Temperature Sensor Probe Applications

  • Environmental monitoring.
  • Weather stations.
  • Ice detection systems.
  • Irrigation and sprinkler systems.
  • Temperature monitoring of bulk foods.

Soil Temperature Sensor Probe Features

  • Low cost .
  • No need to calibrate.
  • Rugged design for long term use. 
  • Small size. 
  • Consumes less than 3mA for very low power operation.
  • Precise measurement.
  • Output Voltage is linear to temperature. 
  • No complex Steinhart-Hart equations are needed to convert voltage to temperature. 
  • Wide supply voltage range. 
  • Can be buried and is water proof. 
  • Probe is long and slender for wider use, including smaller potted plants.

Other Vegetronix Products of Interest

Soil Temperature Sensor Probe Pricing and Ordering Info

Contact us for pricing information. 

Part Number Description Price Purchase
THERM200-2M  Soil Temperature Sensor Probe - 2 meter Cable $33.95 Buy THERM200 Now
THERM200-5M  Soil Temperature Sensor Probe - 5 meter Cable $40.95 Buy THERM200 Now
THERM200-10M  Soil Temperature Sensor Probe - 10 meter Cable $50.95 Buy THERM200 Now

Soil Temperature Sensor Probe Specifications

THERM200 Temperature Sensor Probe

Power consumption < 3mA
Supply Voltage 3.6V to 20 VDC.
Dimensions See drawing below.
Power on to Output stable 2 seconds
Output Impedance 10K ohms
Operational Temperature -40ºC to 85ºC
Accuracy ±0.5°C 
Resolution 0.125ºC
Output Voltage Range 0V to 3V linear to temperature
Voltage Output Equation Temperature (ºC) = Vout*41.67 -40
Temperature (ºF) = Vout*75.006 -40
Cable Length 2 meters


Soil Temperature Sensor Probe Wiring Table

Bare Ground
Red POWER:  3.6V to 20 VDC.
Black OUT: 0 to 3 linear to temperature

Soil Temperature Sensor Probe Drawing

THERM200 Soil Temperature Sensor Probe Drawing

THERM200 Soil Temperature Sensor Drawing


Soil Temperature Sensor Probe Frequently Asked Questions (FAQ)

1. Where is the temperature sensing element on the probe?
  The temperature sensor is inside of the blue enclosure.
2. Do I need to bury the probe to measure soil temperature, or can I just insert the blade?
  You need to bury the probe to measure soil temperature, otherwise, if you merely insert the blade, you will be measuring air temperature, not the soil temperature.
3. Can the sensor read rapid fluctuations in temperature?
  No. The probe is intended for measuring soil temperature, and typically ground soil does not change temperature rapidly.  Likewise the temperature sensor has a high thermal mass because of its waterproof enclosure, and so it make take 15 minutes or more to settle after a rapid external temperature change.

This does not mean that you need to power the sensor for 15 minutes before taking a reading.  It means that it takes some time for the center of the probe to reach the same temperature as the soil in which it has placed.


How to Get Started with the Soil Temperature Sensor Probe

The best way to get started is to order a few sample soil temperature sensor probes and try them out in your application.  Please use our online ordering system to purchase units. 

Buy THERM200 Now

 Soil Temperature Sensor

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