| Intermediate Technology Education | Energy and Power Technology | Pre-Design | Topic 3 | Optional Activity 4 |

Electrical Energy Measurement

Measuring the Energy

You will need

  • EM100 Energy Meter
  • Test Appliances

Setting up the Meter

Figure. Multi function energy meter

Before you start, find out how much a kilowatt-hour is worth. This is printed on your monthly energy bill.

You will need to make sure the unit is reset. Remove the battery pack for a minute and the display should reset. Be careful replacing it—the battery pack can only go in one way.

Start by setting the price per kilowatt-hour in the unit.

  • Click the ↓ button twice. The small message over the middle display should read Price / KWh       $.
  • Click the Price button. The middle display will change to 000.000 and the first 0 should be blinking. Keep pressing the Price button until the second digit to the right of the decimal place is blinking 000.000. (If your cost is more than 9 cents you need to set the first digit after the decimal).
  • Click the ↓ button until this digit is set to the cost. In the previous example the cost was $0.09. If this is what's on your energy bill, the display should look like 000.090.
  • If your last digit is not 0 set that as well. Press the Price button until the display looks like 0.090 (or whatever your rate is).

Get Ready to Measure

Choose a convenient appliance that runs on 120 V AC (the larger the better) and record any electrical information that may be printed on its sticker such as Amps (Amperes), Volts, and Watts.

Print the table (see link below). It will provide a convenient way to record the various measurements. (If you use spreadsheets you might look at the table and set up a "sheet" to record the measurements electronically.)

Table

Plug the meter into the receptacle and plug the appliance into the meter. It would be good if you can leave the meter on the appliance for several hours (a full day would be even better).

Read the Meter

As soon as the appliance is plugged into the meter (and turned on) the measurements will begin. You can record some preliminary readings in your table.

Press the ↑ button to cycle through the various measurements. Record Volts, Amperes, and Watts. (You don't need to record max Watts or max Amperes. The maximum readings are useful if you have a device that doesn't use a steady current, for example, a heavy motor whose load varies.)

Finish the Measurements

When you reach the end of your measurement time unplug the appliance from the meter. The clock (time window) should stop. Record the total time.

From the middle window record the KiloWatt-Hours used (KWh). Use the ↓ button to cycle through this window and record the Total $ (cost).

If you have other appliances to test, repeat Steps 3 to 5.

Make appropriate entries in your course portfolio.

Questions

  • If there was a sticker on the appliance answer the following:
    • Was the voltage measured close to the sticker voltage?
    • Was the current measured close to the sticker current?
    • Was the power measured close to the sticker power?
  • What was the cost of running the appliance per hour? (Use the formula Time / Cost. Convert minutes to hours and a fraction of an hour.)
  • If the appliance was left on for a month (30 days) how much would it cost.
  • If another person/group measured the same kind of appliance ('fridge, TV, monitor etc.) compare your results.

Make appropriate entries in your course portfolio