2. CONTENTS
• Temperature sensors
1. Types of temperature sensors
2. Working
3. Application
• pH sensors
1. What is pH?
2. Working
3. application
3. TEMPERATURE SENSORS
1. Contact Sensors:
• Measures their own temperature.
• The temperature of the object to which the sensor is in contact is inferred by assuming or knowing that
the two are in thermal equilibrium.
1. Non-contact Sensors:
• Measures the thermal radiant power of the infrared or optical radiation that they receive.
• The temperature of an object is inferred from which the radiant power is assumed to be emitted.
4. CONTACT TEMPERATURE SENSORS
1. Thermistor
Thermally sensitive resistor that exhibits a change in electrical resistance with a change in temperature.
2. Bimetallic strip Thermometers
Different metals expand at different rates as they warm up.
5. NON CONTACT TEMPERATURE SENSORS
Radiation Thermometers (Pyrometers)
Measures temperature from the amount of thermal electromagnetic radiation received from a spot on the
object of measurement.
6. WORKING
• In order to collect data from the sensors, the signals from the sensors need to be converted into digital
numbers that the processor can handle.
• The temperature sensor converts the temperature it is measuring to a voltage that corresponds to the
temperature. The ADC measures the voltage and convert it into a digital number. The computer then
process it to calculate the temperature.
7. APPLICATION
• Freezing temperature alarm.
• Freezer over-temperature alarm.
• Personal computers, mobile phones, automobiles, medical equipment and gaming consoles.
8. PH SENSORS
• What is pH?
It is defined as negative logarithm of hydrogen ions in a solution. In simple words, it determines the acidity
and salinity of a solution.
• pH>7 indicates that the solution is basic.
• pH<7 indicates that the solution is acidic.
• pH=7 indicates that the solution is neutral.
9. APPLICATIONS
• Acid-base titrations.
• Investigation of acid rain.
• Investigation of water quality in streams and lakes.
• Monitoring pH change during chemical reactions.
10. DESIRABLE SOIL CONDITIONS FOR OPTIMUM CROP
PRODUCTION
• pH conditions varies from crop to crop. While some crops grow best in the 6 to 7 range, others grow
well under slightly acidic conditions.
• The ideal condition for maximum crops to grow best is in the range of 5.5 to 7.
• The ideal temperature conditions for planting most plants are 65 to 75 degrees.
