Data logging: The term 'data logging' refers to collecting or gathering data over a period of time. How Data is collected? Sensors are used to take readings or measurements at regular intervals of their environment. The sensors could be collecting data on a wide range of things such as temperature, humidity, pressure, wind speed, water currents, electrical voltage, pH readings etc. The sensors may be either analogue or digital. If they take analogue readings, an Analogue to Digital Converter (ADC) will be needed to convert the signal into digital data which the computer can understand. Data Logger: As the sensor takes a reading, the data is sent though a cable or wireless link to the data logger. The data logger usually stores the data for a period of time before sending it in a large batch to a computer which will process and analyze it. A data logger is often a hand-held battery-operated device which has a large amount of memory. Data Logging Examples : In a Hospital; to monitor heart rate, breathing rate, temperature Water Companies; acidity of water in reservoir, pollution, chemical ratio

Remote Data Logging The data might need to be collected at all times of the day and night or during weekends when people might be away from work. Data might also need to be collected from dangerous places such as volcanoes or from places where it is not practical or safe for a human to be, maybe deep in the ocean, in the upper atmosphere or even on other planets. Remote data logging means that the sensors collect data 'out in the field' and pass it to a portable data logger. The data logger then relays the data either wirelessly, by fibre-optic cables or possibly even by satellite, back to a computer ready for analysis.

A sensor is a device that produces an electrical signal in response to a stimulus. Types of stimulus: The stimulus may be Physical (temperature, light level) Chemical (acidity, presence of gas) Sensors are important components in input devices. They can produce a stream of input data automatically, without any action by a person. A sensors analogue signals can be digitized or converted into digital data by an analogue-to- digital converter (ADC). Some sensors have an ADC built in SensorControl program stimulus

Uses: Data collected by the sensors can be used for: Measurement Monitoring Control Audio or video recording

Switched-based sensors: It is operated by a mechanical contact. It is a very simple, cheap and useful sensor It has just two states, open and close It can provide digital input data directly to a computer Examples: Microswitch, reed switch (operated by a small magnet) Applications: Automatic doors, microwave oven not to turn on while the door is opened Lift doors from opening until the lift has reached the floor Printer paper jam or other faults

Types of sensors Temperature Pressure Light Infrared Humidity Gas

Temperature sensor It produces a signal that depends on the temperature of its surroundings Uses: Measurement Controlling

 Automatic appliances like washing machines Microswitch detects whether the door is shut and opens a water valve to fill the drum Pressure sensor to detect if the drum is full Temperature sensor to check is the water is hot enough. It not causes to turn on the heater and vice versa  Electronic thermometer  Controlling heating system in buildings  Chemical reactions  Greenhouse

Pressure sensor It produces a signal that depends on the pressure it is exposed to. Applications: Automatic blood pressure monitor Chemical reaction vessels to control gas or liquid pressure

Light sensor A light sensor produces a signal that depends on the level of light falling on it. Applications: In automatic cars Robotic truck

Infrared sensor It produces a signal that depends on the level of invisible infrared radiation falling on it. All objects emit significant infrared radiations. Applications: To be used by detectors with simple camera Earth’s surface, oceans and cloud cover from satellites by higher quality IR cameras TV remote controls

Humidity sensor (moisture sensor) It produces a signal that depends on the concentration of water vapours in the atmosphere Applications: Sensor-enabled smart Irrigation system controller Heating, ventilating and air conditioning system(HVAC) in a library or a museum in order to prevent excessive humidity in the air Greenhouse to control moisture level Forecasting in weather stations

Gas Sensor It produces a signal depending on the concentration of a particular gas or vapour Applications: To be used for an inflammable gas like Liquid propane gas(LPG) that could cause explosion. It sounds an alarm if there is a leakage. Process control in chemical industry Environmental control of air pollution

Advantages of using sensors They can collect data far more frequently than a person Data logging is often more accurate because there is no likelihood of human error More accurate than a person who may misread the signal Can collect data from places where it is difficult to go for a person like remote areas or nuclear reaction vessels Data logging can be carried out 24 hours a day, 365 days of the year Time intervals for collecting data can be very frequent and regular, for example, hundreds of measurements per second can be set up to start at a time in the future

disadvantages They may need a power source to work Regular calibration is needed to check their accuracy If the data logging equipment breaks down or malfunctions, some data could be lost or not recorded Equipment can be expensive for small tasks The equipment will only take readings at the logging interval which has been set up. If something unexpected happens between recordings, the data will not be collected.