Keithley 2651A, Reference Manual

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Section 4: Theory of operation Model 2651A High Power System SourceMeter® Instrument Reference Manual
4-4 2651A-901-01 Rev. A / March 2011
P
CS
The maximum power generated in an instrument channel that can be properly dissipated by the
instrument cooling system measured in watts. For the Model 2651A, this constant equals 370.
T
AMB
The ambient temperature of the instrument operating environment.
P
DER
= 3(T
AMB
- 30)
This factor represents the number of watts the instrument is derated when operating in environments
above 30° C. The maximum output power is reduced by 3 W per degree C above 30° C.
P
DER
is 0 when the ambient temperature is below 30° C.
V
OA
The instrument output amplifier voltage. This constant can be found in the tables below.
V
P
The voltage level the instrument is attempting to force while at the pulse level.
When operating in quadrants 1 or 3 (sourcing power), the sign of this voltage must be positive when
used in the power equations.
When operating in quadrants 2 or 4 (sinking power), the sign of this voltage must be negative when
used in the power equations.
V
B
The voltage level the instrument is attempting to force while at the bias level.
When operating in quadrants 1 or 3 (sourcing power), the sign of this voltage must be positive when
used in the power equations.
When operating in quadrants 2 or 4 (sinking power), the sign of this voltage must be negative when
used in the power equations.
I
P
The current flowing through the instrument channel while at the pulse level.
I
B
The current flowing through the instrument channel while at the bias level.
Maximum duty cycle equation
DC
MAX
(
P
CS
– P
DER
)
– |
(
V
OA
– V
B
) (
I
B
)
|
|
(
V
OA
– V
P
)(
I
P
)
| – |
(
V
OA
– V
B
)(
I
B
)
|
NOTE
When attempting to determine the maximum duty cycle, where the off state will be 0 V or 0 A:
I
B
is 0
I
P
and V
P
are the voltage and current levels when the instrument is on
Model 2651A maximum duty cycle equation constants
Constant 100 mV
range
1 V
range 10 V
range 20 V
range 40 V
range
V
OA
18.5 18.5 18.5 27 64