Keithley 2790 User Manual

Model 2790 SourceMeter
®
Switch System User’s Manual 2-9
Math
There is a shortcut math function to calculate low resistance when using the I-source of a
7751/7752/7753 module, and one to calculate high resistance when using the V-source and
I/V amplifier of a 7751/7753 module.
Low ohms calculation (SxIohms)
• SxIohms – Calculates and displays low resistance reading for 7751/7752/7753
module in slot x (where x =1 or 2).
This ohms function is a shortcut for the mX+b calculation. When selected, the following
“m” and “b” factors are used:
m = 1 / I
SOUR
b = 0
Calculation: R = mX + b
= (1/ I
SOUR
) x V
MEAS
+ 0
= V
MEAS
/ I
SOUR
where: I
SOUR
is the programmed current level of the I-source of the 7751, 7752, or
7753.
1 / I
SOUR
is the “m” factor for the calculation (mX+b).
V
MEAS
is the voltage measured by the DMM of the Model 2790. It is the “X”
variable for the calculation (mX+b).
When the SxIohms calculation is selected, the Model 2790 measures voltage (X) and
calculates mX+b using the above factors. The displayed reading will be in ohms (Ω). This
selection also sets DMM to DCV, 1V range.
NOTE SxIohms cannot be selected if the I-source is set to 0mA. Since “m” = 1 / I
SOUR
dividing 1 by 0 would result in an erroneous reading (positive infinity).
When using the low ohms calculation, the highest DCV measurement range that can be
selected is 1V. Attempting to select a higher range will cause error -222 (Parameter out of
range). Attempting to turn Autoranging on generates error -221 “Settings conflict” over
the GPIB or a “NO AUTORANGE” message on the display if done from the front panel
AUTO key.

Keithley 2790 Specifications

General

Brand	Keithley
Model	2790
Category	Switch
Language	English