Choosing Run Parameters - Amersham Pharmacia Biotech EPS 601 Manual Del Usuario

EPS 601 - User Manual
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 601 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
P = U x I
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
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.
10
Select MORE by
(1)
(2)
(Ohm´s law)
A
SET: P2
600 V 50 mA
more
MORE: P2
Select program
Select by
Confirm by
enter
Current check at
start? YES/no
Select by
Confirm and
enter
Exit by
A
SET: P2
600 V 50 mA
2:00 h
30 W
2:00 h
30 W