What are Environmental Sensors?
Environmental sensors are generally small devices that measure environmental parameters such as air, water, and soil. The main objective of environmental monitoring is to minimize the impact of activities of human beings on the environment and to mitigate the harmful effects on health. The advantages of air quality measurement lies in the ability to improve quality of life.
Objectives of environmental monitoring are to identify source of contamination, confirm and reconfirm the success of pollution control measures, and collect meaningful environmental data such as air quality measurement to understand more about different sources of pollution.
Air Quality Sensors: Particulate matter sensors
Particulate matters are particles in the air and they mainly dust, soot, and the rest, which range from minute particles viewed through a microscope to the ones visible to the naked eye. These include tiny particles called PM10 which has a diameter of around 10 micrometers and PM2.5 with a diameter of about 2.5 micrometers. These particles, when inhaled, can cause damage to respiration and enters the bloodstream causing disruptions. It forms the basis of the Air Quality Index. Measuring them is essential, and since accuracy is of great concern, Ambee uses sensors that work on the laser scattering principle.
The sensors produce scattering by using a laser to radiate suspending particles in the air. They then collect scattering light to a certain degree to obtain the curve of scattering light change with time. In the end, the microprocessor can calculate equivalent particle diameter and the number of particles with different diameters per unit volume.
A temperature sensor is a device designed to measure an object’s degree of heat or cold. The function of the thermometer depends on the voltage across the diode. The temperature change is directly proportional to the resistance of the diode. The lower the temperature, the lower the resistance, and vice versa. Ambee uses Platinum Resistance Temperature Detector with exceptional precision, linearity, stability, and reproducibility. The probe consists of a thermistor epoxy with a matching resistance-temperature curve encapsulated in a copper tube for faster thermal response and environmental protection. The flat tip of the tube allows it to be mounted on a reasonably flat metal or concrete surface to measure surface temperature.
Ambee uses capacitive-based humidity sensors owing to their accuracy and stability. The relative humidity is measured by placing a thin strip of metal oxide between two electrodes. The metal oxide’s electrical capacity changes with the atmosphere’s relative humidity.
Wind speed and direction sensors:
Ambee uses a cup-based anemometer to measure wind speed with a vane attached to measure the direction of the wind. A 20k linear potentiometer is attached to the wind vane. The output of the wind direction circuit is connected to the analog pins of the microcontroller. The power consumption is low for the cost, and the measurement accuracy is high. To measure the wind speed, the wind cup has a reed switch mounted near the shaft. This switch is activated once for each rotation of the cup. To calculate the wind speed, apply an equation that converts the number of switch activations per period to kilometers per hour. The cup is attached to a horizontal arm with the help of a vertical rod that rotates around an axis. A shaft located inside the shaft rotates the cup. It is an interrupted based, which means for a full rotation of the cup, a pulse is generated on one of the pins of the sensor.
Figure: Vane shows direction based on ADC conversion
Total Organic Volatile Compound Sensors:
TVOC is the sum of all VOCs present in a given environment. MOX technology is used in Ambee sensors for measuring TVOCs. A MOX sensor is a heated surface of a metal oxide that changes its electrical resistance depending on the oxygen content on its surface. Oxidizing gases like NOx (providing more oxygen than ambient air) increase the resistance, whereas reducing gases like VOCs (consuming oxygen by being combusted on the metal oxide surface) reduce the resistance.
Figure: Working principle of MOX sensors
Ambee uses tipping bucket sensors to measure the amount and intensity of rainfall. The tipping bucket rain gauge consists of:
- A funnel to direct the water into the bucket
- Two connected buckets
- A pivot point between the buckets to enable them to tip
- Calibration screws or stop sensors to record each dip; and
- Drainage holes to remove recorded rain.
Water drips into the funnel at the top of the rain gauge when it rains. The funnel guides water to the top of the two fall buckets. Tumble buckets have water limits specified by the manufacturer or operator. When the collected water reaches a predefined limit, the bucket will tip over and hit the calibration / stop screw. Meanwhile, the second bucket is lifted and begins to fill. Even if it rains, the filling and tipping process continues. The switch activates when the bucket pans and presses the stop/calibration screw, and rain information is recorded electronically. The device calculates the number of times the switch is triggered and already knows the amount of rainfall needed to fill each bucket, so the sensor displays the correct amount of rainfall.
Given that most individuals spend 90% of their time inside, indoor air pollution can be up to eight times higher than outside air pollution; and because recent design trends favor airtight rooms, indoor air quality should be a top priority. Poor air quality can cause severe fatigue, headaches, eye discomfort, and loss of focus (also known as sick-building syndrome), and many individuals are unaware of it. However, environmental sensing has the potential to alleviate such suffering.
Environmental sensors backed with Weather API and other datasets, can be utilized in a number of smart home devices such as thermostats, all of which can be managed from your smartphone thanks to the Internet of Things. These technologies work together to maximize your degree of comfort. You can control your heaters, air conditioners, and windows remotely with the push of a button. Context awareness enables your gadgets to understand which environment best meets your needs and store that information for later use. Indoor air quality monitoring ensures productivity and relief in schools, companies, and residences.
Environmental monitoring allows us to explore the infinite opportunities connected with recent advancements in MEMS technology; they can detect what our bodies cannot. When will you begin sensing your surroundings?