Keithley 2520, User Manual, Page: 102 / 329

Model 2520 User’s Manual Range, Filter, and Math 6-7
Conductance
This math function computes the conductance from the ratio between the laser diode cur-
rent source value and the measured voltage:
Conductance = I
L
/V
L
where: I
L
= laser diode source current
V
L
= measured laser diode voltage
Resistance
This math function computes the resistance using the ratio between the measured laser
diode voltage and the source current:
Resistance = V
L
/I
L
where: V
L
= laser diode voltage measurement
I
L
= laser diode source current
Power
This math function calculates power using the measured voltage and source current values
as follows:
Power = V
L
×
I
L
where: V
L
= laser diode voltage measurement
I
L
= laser diode source current
MX + B
This math function multiplies the measured laser diode voltage or photodiode detector
current by an offset factor and adds an offset value as follows:
Reading = MX + B
where: M = gain (slope) factor
X = measured laser diode voltage (V
L
) or photodiode current (I
PD
)
B = offset value
Delta (remote only)
This math function computes the difference between detector #1 and detector #2 current:
Delta = I
PD1
- I
PD2
The calculation is performed point-by-point on individual A/D samples, not on the final
current measurement. Delta is available using the CALC4 subsystem (See
Section 14 ).