Accuracy of hourglass Sand Timers

Study the accuracy of sand timers

Introduction: Hourglasses are among a number of ingenious timekeeping devices used before the development of clocks in the Middle Ages. Hourglasses, also called sandglasses, sand timers, sand clocks, or egg timers, are a relatively recent invention.

The earliest known record of hourglasses dates from the 14th century. Hour glasses were commonly used as timers in early factories. When working with metals the hourglass aided the tradesman in knowing when just enough heat had been applied to accomplish the desired effect. The hourglasses needs to be carefully calibrated. The hourglass maker must test the instrument and fine tune it to measure the correct length of time.

There are many factors that contribute to the ability of an hourglass to accurately measure time. The type and quality of sand is key. It must have a rate of flow that does not fluctuate. Sand that is too coarse will wear away the glass, eventually making the neck too large. Most important is the ratio of the neck (the hole, or tube) width to the diameter of the sand particles.

Here are the other factors that affect the accuracy of an hourglass:

• The amount or volume of sand used
• The size and angle of the glass bulbs
• The quality of the sand or granular material. It must be fine, dry and consistently formed so it can flow smoothly. (Some substances used in the past were fine grain sand, powdered eggshells, and powdered marble.)
• The width of the neck
• A tight seal so no moisture can get into the chambers. Moisture can add weight to the sand or clog up the neck.
• A flat and level surface on which to rest the hourglass

We still use the hourglass to keep track of time. Just think of its many uses for cooking and for playing games!

Question, Purpose or objective of the project:

Are sand timers accurate? The purpose of this project is to study the accuracy of sand timers by comparing them with each other and a modern clock.

Materials:

You will need the following materials for your experiment.

• 10 identical sand counters (Available from MiniScience online store)
• One clock or watch that can show minutes and seconds
• Paper, ruler and pencil to record your results.

Project Variables:

• The independent variable is the hourglass
• The dependent variable is the cycle time
• Constant is the nominal cycle of hourglass timers. For example 3-minute timers.

Procedure:

1. Get 10 small hourglasses of the same type and the same size
2. Tape the hourglasses to the side of an empty box.
3. Number the hourglasses from 1 to 10
4. Place the box on the table and wait until the sands enter the lower bulb in all hourglasses.
5. Turn over the box and immediately start the timing using your clock. By turning over the box you are turning over all hourglasses at the same time.
6. Watch the hourglasses. As soon as an hourglass completes its cycle and the upper bulb becomes empty, record the time and the number of that hourglass.
7. Repeat the steps 5 and 6 two more times and record your results in a data table like this:

Actual cycle times of 10 identical hourglasses:

After you complete your three trials, calculate the average cycle time for each counter. To do that add the times you entered for the three trials of each hourglass and divide the sum by three. Enter the averages in the last row of your data table.

Draw a graph:

You may make a bar graph to visually present your results. Bar graphs are easy to understand and are appropriate for data that are not directly related to each other.

To construct your bar graph, use one vertical bar for each hourglass you test. Number the bars from 1 to 10 to correspond to the number of hourglasses you have tested. The height of each bar represents the average cycle time for the corresponding hourglass. For example you may draw a vertical line that is 189 millimeters to show a timing cycle of 189 seconds (that is equivalent to three minutes and 9 seconds.)

Draw a conclusion:

In your conclusion write if the sand timers are accurate.  Describe what are the problems with sand timers and why they are not as accurate of mechanical and electronic timers and clocks.

References:

http://www.tkyoung.com/history.html

http://www.loc.gov/rr/scitech/mysteries/hourglass.html

http://www.dencities.com/denmall/denmall-unique8a.html

Order hourglasses online. They come in sets of 10. For a limited time you will receive at least one extra hourglass with each set you purchase. Secure Online Store