7-4 Relative and Math
Math operations
Math functions
The SourceMeter has built-in math functions to calculate the following:
• Power
• Offset Compensated Ω
• Varistor Alpha
• Voltage Coefficient
• Percent Deviation
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:
Power = V × I
where: V = measured voltage
I = measured current
Offset-compensated Ω
The presence of thermal EMFs (V
EMF
) can adversely affect low-resistance measurement
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 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.”
This two-point measurement method is mathematically expressed as:
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).
You will be prompted to enter the two I-Source values. See Front panel math operations.
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