Model 2657A High Power System SourceMeter® Instrument Reference Manual
Section 4: Theory of operation
2657A-901-01 Rev. B/December 2012
4-3
General power equation
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 2657A, this constant equals 200.
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 table 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
Use this equation to determine the maximum duty cycle when operating the instrument in an ambient
temperature (T
AMB
) above 30 °C.
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 2657A maximum duty cycle equation constant
Constant 200
V
range
500 V
range
1500 V
range
3000 V
range
V
OA
1650 1650 1650 3300
|
(
V
OA
– V
P
)(
I
P
)
| DC
MAX
+ |
(
V
OA
– V
B
)(
I
B
)
|
(
1 – DC
MAX
) (
P
CS
– P
DER
)
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
Summary of Contents for 2657A
Page 3: ......
