Ratio and Delta 5-9
Selecting Delta
Delta is selected by pressing the SHIFT key and then the V1-V2 key. The “(Vt1-Vt2) / 2”
message appears briefly before displaying the result of the calculation. Delta is disabled by
selecting a single measurement function (DCV1, DCV2, TEMP1, or TEMP2) or by selecting
Ratio.
NOTES
•To double the speed of Delta measurements, disable Front Autozero as
follows:
Press
SHIFT
> Press
CONFIG
> Set
FRONT AUTOZERO
to
N
>
Press
ENTER
For details on Front Autozero, see “Autozeroing modes” in Section 2.
• Delta reading is indicated by a small “d” on the display (after the reading).
• Delta performs voltage measurements on Channel 1. If on Channel 2, the
Model 2182 will automatically go to Channel 1 when Delta is selected.
• Delta readings can be stored in the buffer. See Section 6 for details on using
the buffer.
• Delta cannot be selected if stepping or scanning.
• Reading HOLD cannot be used with Delta.
Delta measurements by the Model 2182 require the use of an alternating polarity source. The
source must have external triggering capabilities that are compatible with the external triggering
capabilities of the Model 2182. The following procedure shows how to use a Keithley
SourceMeter with the Model 2182 to perform Delta measurements.
Delta measurement procedure using a SourceMeter
A Keithley SourceMeter (Model 2400, 2410, or 2420) can be used as a bipolar source by
configuring it to perform a custom sweep. In general, a custom sweep is made up of number of
specified source points. To provide current reversal, the positive current value(s) are assigned to
the even numbered points, and the negative current value(s) are assigned to the odd numbered
points. For details on custom sweep, see the User’s Manual for the SourceMeter.
Applications that use Delta measurements require either a fixed current or a growing
amplitude current. When a fixed current is required, the SourceMeter can be configured to output
a bipolar 2-point custom sweep. That sweep can be run a specified number of times or it can run
continuously. For example, if a fixed current of 1mA is required for the test, the two bipolar
sweep points for the custom sweep would be +1mA and –1mA.
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