Tektronix Keithley 2651A Reference Manual page 222

Section 4: Theory of operation
General power equation
V The instrument output amplifier voltage. This constant can be found in the table in
OA
Maximum duty cycle equation
V The voltage level the instrument is attempting to force while at the pulse level.
P
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 The current flowing through the instrument channel while at the pulse level.
P
V The voltage level the instrument is attempting to force while at the bias level.
B
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 The current flowing through the instrument channel while at the bias level.
B
P The maximum power generated in an instrument channel that can be properly dissipated
CS
by the instrument cooling system, measured in watts. For the Model 2651A, this constant
equals 370.
P = 3(T
DER AMB
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 is 0 when the ambient temperature is below 30 °C.
DER
T The ambient temperature of the instrument operating environment.
AMB
Maximum duty cycle equation
The following equation applies to both channels, sinking or sourcing power simultaneously. If a duty
cycle less than 100% is required to avoid overheating, the maximum on-time must be less than 10
seconds.
When attempting to determine the maximum duty cycle, where the off state will be 0 V or 0 A:
▪
I is 0
B
▪
I and V
P P
Model 2651A maximum duty cycle equation constants
Constant
V
OA
4-4
Model 2651A High Power System SourceMeter® Instrument Reference Manual
(on page 4-4).
- 30)
are the voltage and current levels when the instrument is on
100 mV 1 V
range range
18.5 18.5
10 V 20 V
range range
18.5 27
40 V
range
64
2651A-901-01 Rev. C October 2021