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5 Operation
20
1. Enter MORE
2. Select program
3. Choose current check no
4. Back to SET mode
Fig 5. Disabling the current check.
5.5
Choosing run parameters
EPS 3501 is an automatic cross-over power supply that allows the user to set limits for
voltage, current and power. During electrophoresis, only one of the parameters is limiting
at a time. The limiting parameter determines, together with the conductivity in the
electrophoresis system, the values for the other two parameters. Voltage, current, power
and conductivity are related by the following equations:
U = I / L
(1)
P = U x I
(2)
Where U = Voltage, I = Current, P = Power and L = Conductivity
Equation (1) is more familiar if the conductivity is replaced by the reciprocal
resistance (R):
U = R x I
(Ohm´s law)
The electric field E, measured in V/cm, is the driving force behind electrophoresis.
E = U / d
where E = Electrical field strength, U = Voltage, d = distance
The electrical field strength is achieved by applying a voltage. The higher the voltage, the
faster the electrophoresis. Fast electrophoresis is beneficial since it counteracts diffusion.
The disadvantage of increasing the voltage too much is that most of the generated
electrical energy, the product of power and time, is transformed to heat. Therefore
cooling of electrophoresis equipment is recommended. Cooling will also reduce "smiling"
effects which are caused by mobility differentials across an electrophoresis gel resulting
from poor heat transfer. Since the cooling efficiency cannot be increased indefinitely, the
power should be limited when programming the power supply.
Electrophoresis Power Supply EPS 3501 User Manual 18-1130-21 Edition AD
A
SET:
P2
3000 Vh
2500 V
50 mA
30 W
Select MORE by
more
MORE:
P2
Select program
Select by
Confirm by
enter
Current check at
start?
YES /no
Select by
Confirm by
enter
Exit by
A
SET:
P2
3000 Vh
2500 V
50 mA
30 W
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