SEP Energymeter
SEP Energymeter
SEP Energymeter instructions v3
SEP Energymeter
THE SEP ENERGYMETER
The SEP Energymeter has been designed to enable students to make
measurements of energy and power in low-voltage circuits
(up to 20 volts maximum).
Different measurements can be made by pressing the function button to cycle
through the following four settings:
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Energy (also displays time)
Power
Average power (also displays energy and time)
V, I and P (voltage, current and power)
To make the energymeter simple to use, the display is ‘autoranging’ – that is, the
units in which values are displayed change automatically (e.g. between joules
and kilojoules) and the decimal point automatically shifts so that three significant
figures are always displayed. This means that it can be used to measure anything
from 0.000 01 joules to 400 000 joules without the need to make any manual
adjustments.
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SEP Energymeter
GETTING STARTED
For simplicity, there is no switch on the
energymeter itself, so firstly the mains adapter
should be plugged into the mains socket and
the lead inserted into the energymeter, before
switching on at the mains.
If the meter is being used make measurements, for example, on the energy and
power in a circuit with a battery and bulb, then the battery should be connected
to the ‘source’ terminals and the bulb should be connected to the ‘load’ terminals.
The energymeter is now ready to use.
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SEP Energymeter
MEASURING ENERGY
Press the function button to obtain the ‘Energy’
setting. The default display shows energy in
joules (J) and time in seconds (s).
Press the ‘start/pause’ button to start measuring
energy. Note the ‘run’ icon in the bottom right
corner of the display.
To pause the measurement at any time, press
the start/pause’ button again. Note that the
icon changes.
To set the display back to zero, press the ‘reset’
button.
If the value for energy is less that 1 J, it is displayed in millijoules (mJ); when it reaches
1000 J, it is displayed in kilojoules (kJ).
The maximum value of ‘time’ is 9999 s. With the maximum recommended value for
the power (40 W), the maximum energy that can be measured over this time period is
about 400 kJ.
MEASURING POWER
Press the function button to obtain the
‘Power’ setting. The default display shows
power in watts (W). The value given on this setting shows the
power at a particular moment in time (i.e. an
instantaneous reading).
If the value for power is less that 1 W it is displayed in milliwatts (mW). The maximum
recommended value for power is about 40 W.
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SEP Energymeter
MEASURING AVERAGE POWER
Press the function button to obtain the
‘Average power’ setting. The default display
shows average power in watts (W), and the
two values from which it is calculated - energy
(J) and time (s).
Press the ‘start/pause’ button to start measuring
average power. Note the ‘run’ icon in the
bottom right corner of the display.
To pause the measurement at any time, press
the start/pause’ button again. Note that the
icon changes.
To set the display back to zero, press the ‘reset’
button.
If the value for the average power is less that 1 W, it is displayed in milliwatts (mW).
MEASURING VOLTAGE, CURRENT AND POWER
Press the function button to obtain the ‘V,I and
P’ setting. The default display shows the voltage
across the source in volts (V) and the current
through the circuit in amps (A). These two values
are used to calculate the power in watts (W).
The value given on this setting shows the
power at a particular moment in time (i.e. an
instantaneous reading).
If the value for current is less that 1 A, it is displayed in milliamps (mA).
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SEP Energymeter
WHAT HAPPENS IF THE MAXIMUM VOLTAGE IS EXCEEDED?
The maximum voltage that can be measured by the energymeter is 20 V. If this value is
exceeded, then the error message ‘OVER’ will appear. Note that excessive voltages (over
50 V) may damage the instrument.
If the voltage is exceeded when the function
is set to ‘Power’ then the value of power is
replaced by the word ‘OVER’.
If the function is set to ‘V, I and P’ then the
values for both voltage and power will be
replaced by the word ‘OVER’.
If the voltage is exceeded while energy is being
measured, then the value of energy is replaced
by the word ‘OVER’. In addition, a ‘?’ icon
appears in the top right corner.
If the voltage subsequently drops below 20 V,
the value for energy will reappear, but the ‘?’
icon remains.
This indicates that the voltage has at some
point been exceeded, and that the energy value
is no longer accurate. However, if the voltage
was only exceeded for a brief time, then the
experiment could be continued with only a
slight loss of accuracy.
In the same way, ‘OVER’ and the ‘?’ icon also
appear if the voltage is exceeded while average
power is being measured.
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SEP Energymeter
WHAT HAPPENS IF THE SOURCE IS CONNECTED THE WRONG WAY ROUND?
If the source is connected the wrong way
round (for example, the -ve end of a battery is
connected to the red terminal and the +ve end
to the black), then the error message ‘Source
current wrong direction’ appears.
This message can also appear, for example, if a hand-turned generator is turned
backwards, or if the voltage on a power pack is suddenly turned down to zero.
TECHNICAL INFORMATION
Power supply DC supply of 9 to 13 volts, current requirement about 300mA, standard
2.1mm power connector. If the energymeter is to be used in the field, then it could be
powered using 8 x AA batteries.
Maximum voltage and current of source The maximum voltage that can be recorded by
the instrument is 20 V; voltages above 50 V may damage the instrument. The maximum
recommended current is 2 A (though the instrument is sufficiently robust to withstand
currents a little above this for a short period of time, for example, if using 9 V across the
source with an accidental short across the load).
Sensitivity The smallest values that can be displayed for each of the measurable quantities
are 0.01 mJ, 0.01 mW, 0.01 mV and 0.01 mA respectively.
Accuracy The accuracy of the instrument is approximately ±1% for voltage and ±2% for
current.
Refresh rate and smoothing The display is refreshed every 0.5 seconds. The current and
voltage are constantly sampled; the values displayed represent the average values from the
0.5 second period before the display is refreshed.
Variations in ‘source’ voltage The power readings given by the energymeter should be
fairly constant for circuits using batteries or smoothed and regulated low-voltage power
supplies; however, if the power supply is not smoothed and regulated (check this in its
manual), then there can be considerable differences in the power readings from one value
to the next (though values of energy can still be used since these are cumulative).
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SEP Energymeter
FURTHER INFORMATION
The SEP Energymeter was developed by the Gatsby Science Enhancement Programme
in conjunction with Middlesex University Teaching Resources. There is also an SEP
booklet ‘Making energy real: using the SEP Energymeter’ that gives further details
about curriculum applications with examples of student materials. Visit the SEP website
(www.sep.org.uk) for information on curriculum resources and how to become an SEP
Associate. Copies of the booklet ‘Making energy real’ can be purchased from Middlesex
University Teaching Resources (www.mutr.co.uk).
Gatsby Science Enhancement Programme
Middlesex University
S37 Stable Yard
Bramley Road
London N14 4YZ
Email: info@sep.org.uk
Web: www.sep.org.uk
Teaching Resources
Middlesex University
Unit 10, The IO Centre
Lea Road, Waltham Cross
Hertfordshire EN9 1AS
Tel: 01992 716052
Fax: 01992 719474
Email: sales@muventures.co.uk
Web: www.mutr.co.uk
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