Keithley 2565 Noise in Lo 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: Noisy Readings in Low Resistance Measurements Probable Cause: Changing magnetic fields can come from B. Consider using shielded twisted pair Magnetic Interference local AC currents in the test system or from cables. At the very least, run leads close The most common cause of noisy low the deliberate ramping of the magnetic field, together. resistance measurement is magnetic interfer- such as for magnetoresistance measurements. C. Tie down the cables to minimize move- ence. Relative motion can come from something ment. Low resistance measurements are, in that seems as harmless as dangling leads, D. If necessary, shield the test setup with Mu general, low voltage measurements, and are which can generate nanovolts as they move in metal, a special alloy with high perme- susceptible to the low voltages generated by the earth's magnetic field. To avoid this in ex- ability at low magnetic flux densities. magnetic interference. Faraday's law states tremely sensitive voltage measurements, the E. Filter out AC signals from magnetic fields that a voltage will be induced in any conduc- leads must be kept short and rigidly secured. at the input of the instrument. tor exposed to a changing magnetic field. F. Try moving the instrument farther from This can happen in two ways: Remedies the source of an interfering magnetic 1. The field changes with time. A. Use twisted pair cables, which reduce the field. 2. There is relative motion between the cir- enclosed area in the magnetic field and cuit and the field. minimize the induced voltage. 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. Keithley Instruments, Inc. 28775 Aurora Road