Math Operations - Keithley 6430 Instruction Manual

7-4 Relative and Math

Math operations

Math functions
The SourceMeter has built-in math functions to calculate the following:
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The Power and Percent Deviation math functions use a single voltage and/or current mea-
surement to perform the calculation. The Offset-Compensated Ω, Varistor Alpha, and Voltage
Coefficient math functions require 2-point measurements to perform a calculation.
Power
This math function calculates power using the measured voltage and measured current val-
ues as follows:
where:
Offset-compensated Ω
The presence of thermal EMFs (V
accuracy. To overcome these unwanted OFFset voltages use the Offset Compensated Ω mea-
surement method. In general, this method measures resistance (V/I) at a specific I-Source level
and then subtracts a resistance measurement made with the I-Source set to a different level
(typically zero).
NOTE
This two-point measurement method is mathematically expressed as:
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You will be prompted to enter the two I-Source values. See Front panel math operations.
Power
Offset Compensated Ω
Varistor Alpha
Voltage Coefficient
Percent Deviation
Power = V × I
V = measured voltage
I = measured current
Offset-compensated Ω is also available from the CONFIG OHMS menu structure.
Using Offset-Compensated Ω from this menu automatically selects zero as one of the
source values. For details, see Section 4, "Offset-compensated ohms."
Offset-Compensated Ω = ∆V / ∆I where ∆V = V2 – V1 and ∆I = I2 – I1.
V1 is the voltage measurement with the I-Source set to a specific level.
V2 is the voltage measurement with the I-Source set to a different level (typically zero).
I1 is the current measurement with the I-Source set to a specific level.
I2 is the current measurement with the I-Source set to a different level (typically zero).
) can adversely affect low-resistance measurement
EMF