Instruction Manual peqPOWER 250 Volt Power Supply
3.
Press the Mode key to migrate to the next parameter.
4.
When the parameter is selected use the
▼▲
arrow keys to increase or decrease the values.
CHOOSING LIMITING PARAMETER SETTINGS
Introduction
The peqPOWER 250 Volt Power Supply is capable of operating at limiting Voltage, or limiting Current
or limiting Power. We recommend operating the peqPOWER 250 Volt Power Supply at limiting voltage
for most applications. See below for more details.
Voltage Limiting
For most electrophoresis methods resistance increases throughout the run. Limiting the voltage provides
the following advantages:
Current and power decrease throughout the run, providing an improving margin of safety over
time.
The same voltage setting can be used regardless of the number or thickness of gels being elec-
trophoresed.
Current Limiting
Discontinuous buffer systems and, to a lesser extent, continuous systems increase resistance during the
run. If you use the current limiting setting on the peqPOWER 250 Volt Power Supply, the voltage will
increase as resistance increases to satisfy Ohm’s law (V=I*R). If no voltage limit is set and a local fault
condition occurs, such as a poor connection, very high local resistance may cause the voltage to in-
crease to the maximum capacity of the power supply. This may lead to local overheating and damage
to the electrophoresis cell or create unsafe conditions. When operating under constant current condi-
tions, set a voltage limit on the power supply at or slightly above the maximum expected voltage.
Power Limiting
Power P is a function of voltage V and current I P=I*V. If voltage is increased power will also be in-
creased depending on the gel system, resistance R should be a constant. Power will be reflected by the
heat generated during a gel run. The power limiting function may be used when running sequencing
gels to remove the APS from the wells and to heat the gel to an optimal temperature for DNA separa-
tions.
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