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April 10, 2017

What is a sensor?

ADI sensor

(Above photo: This sensor from Analog Devices measures micro climate in a hoop house.)

When I began my journey into the work of the Internet of Things (IoT), I thought I knew what sensor was: a thing that measures something. As an engineer, I realized that the “I know it when I see it” definition was too subjective. At LABS, we need a consistent way to talk to a wide range people — technical and non-technical about — what sensors are, what they can do and why they are about to transform everything.

I found that many of the explanations and resources about sensors were great for engineers and scientists but lacking easy-to-understand terms for general managers at mid-sized manufacturing companies, CSA farm operators or local Fire Chiefs.

At LABS, we are working on a number of terms and definitions to help explain what we do, why and how. Today I will talk about sensors.

Measurements

Before defining a sensor, I want to define measurements. Defining measurements separately from a sensor allows us to talk about the various sets of data that might come from a single sensor.

A measurement:

  • Has 1 observable property
  • Has 1 sampled medium (does it measure water, air, soil?)
  • Has a unit of measurement(degrees celsius)
  • Has accuracy, range and precision

Sensors


To define what is a sensor, we use the following criteria. A sensor:

  • Captures at least 1 measurement (What does the sensor tell us?)
  • Delivers data in at least 1 output protocol (language) (How does it get data out to the world?)

 

ADI data

This phone is used to output the data generated by the sensor.

 

Sensors are a key component of many LABS Pilot projects.

In indoor environments such as greenhouses and hoop houses, sensors help us monitor natural climate differences to optimize the growing of more finicky plants and greens. The ADT7420 from Analog Devices one such sensor, commonly used in industrial applications where high resolution is critical. Another sensor that we use indoors is Aeotec’s MultiSensor 6.

For outdoor applications, such as monitoring the microclimate in a vineyard, we use Davis’s Vantage Pro2 Weather Station. The host believes that knowing the actual conditions in his field (not a weather station miles away) will allow him to make better decisions about his vines.

To learn more about sensors, I recommend the following resources:

Open Connectivity Foundation: https://openconnectivity.org/
OneM2M: http://www.onem2m.org
SensorML: http://www.opengeospatial.org/standards/sensorml
WaterML: http://www.opengeospatial.org/standards/waterml

Post by Dan Mahoney, engineering lead at LABS