Computer Data Logging and Control

Lesson Objective:Understand the main terminology based about Data Logging and Models

Learning Outcome:Complete the questions on the worksheet.

Keywords: Data logging, logging period, logging interval, thermistor, thermostat, dedicated system, computer control, feedback loop, DAC ADC

What is happening in this picture?

Measuring temperature change.

Time Temperature

00:30 0.5 ˚C

01:00 0.5 ˚C

01:30 0.75 ˚C

02:00 1.0˚C

02:30 1.0˚C

Recordings would appear like this:

…etc.

How often and how long?

The time interval between measurements is called the logging interval.

The total time taken to take all of the recordings is called the logging period.

What is the logging interval and logging period of this experiment?

Time Temperature

00:30 0.5 ˚C

01:00 0.5 ˚C

01:30 0.75 ˚C

02:00 1.0˚C

…etc.

59:00 21.75˚C

59:30 22.0˚C

60:00 22.0˚C

Logging interval = 30 seconds, Logging period = 60 minutes.

How to determine the logging interval and logging period …

The logging interval depends on how often the data is likely to change. (e.g. the temperature of ice melting into water- every 30 seconds is accurate enough)

The logging period depends on how long it takes for the data to stop changing (60 minutes for ice melting?)

A temperature sensor-Thermistor

Thermistors can be connected to computers and can be used to take temperature recordings over time. You must tell the software the logging interval and the logging period.

Using thermistors

Temperature change turning ice to steam … (using data logging)

Weather stations use data logging equipment.

What do you think is being measured by this remote weather station?

What would the logging interval and logging period be for this?

Why do data logging? Can do it in Inhospitable

places

Records Accurately

Can Record over very long or short intervals

Don’t need Breaks (like humans!)

Easy Acronym:

I

Am

Recording

Boyzone

Control systems

Dedicated Computer Controlled

Feedback Loops The results of the output become part

of the input which can affect the process.

Central heating

Control Systems – feedback

Digital and Analogue

Digital data is stored as 0’s and 1’s

Digital information occurs in steps

Analogue information makes gradual changes

Analogue data can be stored as writing, sound, …etc.

Digital to Analogue Converter

Digital and Analogue signals

Computer

No entry to Analogue

Analogue Signals

Analogue SignalsAnalogue

to Digital Converter

DIGITAL ONLY!

Models and simulations

A model is the re-creation of a process or an object.

A simulation is carried out using a model.

The model must be built or programmed first.

The model is then used to test “real life” situations.

Examples of models

Spreadsheets equations build the model.

Examples of Models

CAD – Graphical image of object

Examples of Models

Virtual Reality

Examples of models

Expert Systems