Keithley 2561 Error in Low Res free download

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A G R E AT E R M E A S U R E O F C O N F I D E N C E Problem: Errors in Low Resistance Measurements Probable Cause: Resistance of the test leads DMM IX Rsourcelead In low resistance measurements, the resistance of the test leads can be a significant fraction of the resistance to be measured, or can Isense (picoamps) Rsenselead even exceed it, and can cause measurement errors. V DUT Remedies Rsenselead A. The four-wire resistance technique--With the four wire resis- tance technique (also called the Kelvin connection), the test cur- Rsourcelead rent is forced through the DUT through one set of leads, while the voltage across it is measured through a separate set of sense leads. Negligible current flows through the sense leads (they are The four-wire resistance technique removes the resistance in the source connected to a high-resistance input on the instrument), so they leads from the measurement loop. do not create any voltage drop, and the voltage measured by the meter is essentially the same as the voltage across the DUT. ohmmeters have a null (Zero, Relative, etc.) function. Short the Note that the voltage sensing leads should be connected as close test leads at the end, then enable the null feature, which will sub- as possible to the DUT to avoid including any of the resistance of tract the test lead resistance from the readings. the test leads in the measurement. One drawback with this technique is that measurement may drift B. Use of the null function on the ohmmeter--Use the two-wire over time, and sometimes it is not practical to keep on "nulling" the resistance technique and null out the test lead resistance. Some test lead resistance to keep the measurement on track. Specifications are subject to change without notice. All Keithley trademarks and trade names are the property of Keithley Instruments, Inc. All other trademarks and trade names are the property of their respective companies.