In IoT, sensors are used to Digitize the

Physical World to bring that information

into the Cyber World

Some users assume the Digital

Readings are Accurate !. There is a need

to understand this Physical World

challenges

Temperature

Thermal Mass of the Temperature Probe limits its

application and can cause in accurate readings

Cannot be used as the

Thermal Mass of IC << that

of the probe

Can be used as

Thermal Mass of Kettle

>> that of the probe

Thermal

Mass Ratio

1: 10 is a

minimum

Temperature

T oC

Temperature

Infra Red

Temperature

Two Temperature sensor measuring same Hot object can

give two different temperature readings

Infra red Temperature sensor is an averaged

measurement from a Radiated surface area

Temperature probe is a localised

Conductive measurement

Temperature

Temperature probe

Aircon draws warn air from top,

passing through temperature

sensor. The heat exchanger

cools the air ,and then exhaust

cool air into the room

Unless you place the

sensor where you stand !

The temperature is

controlled at that air

inlet point, but NOT at

where you are standing

Humidity sensor

Humidity

Readings are affected by Temperature &

Air flow

Placement Height

Wet surrounding affects readings

Humidity

Water Level

Hydrostatic Water sensor affected by

ambient air pressure

Sensor is a flexible membrane to

measure water back pressure

This membrane stiffness is affected by

barnacles

Water Level

7

y = mx + cWa

ter L

eve

l

Voltage

Converts V to

Water Level

Ideal Laboratory Condition Actual Usage

Wa

ter L

eve

l

Voltage

Measurement

Uncertainty

Wa

ter L

eve

l

Voltage

Sensor Drift

Calibration

curve shift

over time

Outdoor Water Level Sensor accuracy challenges Water Level

Air Speed

Anemometer

(Wind Speed) Affected by Placement Location & Height

Need to know sensor placement

High Rise Building

Top ViewSide View

Ultra-Sonic SensorDistance

Affected by Size and Shape of Object (US waves reflects

back) and Humidity (Air density)

LIDAR Photonics

Distance

Affected by Surface texture, Reflectiveness of Object. Laser

goes through glass

Vibration

Vibration

3 Axis X Y Z

Mass can affect readings

Placement is key

Need to know why place

sensor there