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Frequently Asked Questions
What are the relations between Voltage, Current, Power and Resistance?
Power (W) = Voltage (V) x Current (A)
Ω
Resistance (
) = Voltage (V) / Current (A)
How does a power supply react after pressing RUN?
The internal generator will start building up the high voltage at the output ter-
minals while voltage and current are constantly measured and power calculated.
When one of the pre-set parameters is exceeded, the generator stops and will
keep that parameter constant.
How important is the resistance of an electrophoresis unit?
The resistance of an electrophoresis unit depends on its size, gel thickness,
amount of buffer, buffer conductivity and temperature. This resistance will nor-
mally decrease in time due to a slowly increasing temperature. Electrophoresis
units which have a resistance below the minimum load resistance of a power
supply will trigger an alarm! Read the output voltage and current during a run to
measure the resistance and use above formula to calculate the value.
How to keep a constant voltage during a run?
Program the desired voltage and a higher current and power then the maximum
expected values:
Current > Voltage / Resistance
Power > Voltage x Current
How to keep a constant current during a run?
Program the desired current and a higher voltage and power then the maximum
expected values:
Voltage > Current x Resistance
Power > Voltage x Current
How to keep a constant power during a run?
Program the desired power and a higher voltage and current then the maximum
expected values:
Voltage > Current x Resistance
Current > Voltage / Resistance
Why are my output values different from those of a similar experiment?
Either your programmed parameters are not equal to those described or the resist-
ance of your electrophoresis unit is different (see above). It cannot be due to e.g.
an other model of power supply as the relations between Voltage, Current, Power
and Resistance are monitored in the same way by any instrument (the electrical
laws cannot be disregarded!).
What about connecting more than one unit to the same power supply?
The outlets being in parallel each electrophoresis unit will be supplied with
exactly the same voltage. However, current and power may differ due to differ-
ences between them even when exactly the same model, gel, buffers, etc... are
used. Therefore, it recommended to run several electrophoresis units on the same
power supply only in the constant voltage mode.
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EV243
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