Notes on Analog and Digital Measuring Instruments

Analog and Digital Measuring Instruments

• Different types of instruments are used to gather scientific measurements (data).

Types of Measuring Devices

• Measuring devices can be either analog or digital.

Analog Measuring Devices

• Examples: ruler, glass thermometer.
• Usually marked with a series of lines; some of these lines will have numbers next to them.
• These lines and numbers together are called a scale.

Digital Measuring Devices

• Do not have a scale.
• Provide a value that appears directly on the device's screen.
• Examples: electronic kitchen scales, digital thermometers.
• Generally more accurate and easier to use than analog devices.

Quantitative Measurements

• Either analog or digital instruments can be used to make quantitative measurements.

Reading Scales on Analog Devices

• Analog devices (rulers, measuring cylinders, glass thermometers) are marked with a scale.
• Determine what each marking on the scale represents.
• Measurements should always be made with your eye in line with the reading you are taking.

Parallax Error

• Occurs when scales are read from a different angle.
• The reading will be either lower or higher than the true reading.

Sample Problem: Reading a Scale

• Thermometer A: measures 23 degrees.
• Thermometer B: measures 44 degrees.

Data Loggers

• A data logger is a very useful digital device that can measure many different quantities.
• The measurement recorded by a data logger depends on the sensor that is connected to it.
• Example: if a temperature sensor is attached to the data logger, temperature is measured and recorded.

Scientific Investigation: Parallax Problems

• Place a matchstick with the head in line with the 0 mark of a ruler.
• Observe where the end of the matchstick lies on the ruler when viewed from near the head and from directly above.
• There will be a difference between the two lengths, illustrating parallax error.

Measuring a Matchstick

• Measuring incorrectly results in parallax error.
• Measuring correctly requires the eye to be perpendicular to the scale to avoid parallax error.

Exercises:

• Measuring cylinder is an example of an analog measuring instrument.
• Parallax error is when scales are read from a different angle.
• To avoid a parallax error, the measurement should always be made with your eye in line with the reading you are taking.

Analysing Thermometer Scale

• Thermometer measures approximately 33 degrees.
• Thermometer measures approximately 23 degrees.
• Thermometer measures approximately 33 degrees.