Keithley 6487 User Manual

Model 6485 and 6487 User’s Manual Measurements and Sourcing Voltage 3-9
Programming example — current measurements
The following command sequence will perform one zero-corrected current measurement:
*RST ' Return 6485/6487 to GPIB defaults.
SYST:ZCH ON ' Enable zero check.
RANG 2e-9 ' Select the 2nA range.
INIT ' Trigger reading to be used as zero
' correction.
SYST:ZCOR:ACQ ' Use last reading taken as zero
' correct value.
SYST:ZCOR ON ' Perform zero correction.
RANG:AUTO ON ' Enable auto range.
SYST:ZCH OFF ' Disable zero check.
READ? ' Trigger and return one reading.
Model 6487 ohms measurements
Overview
To measure ohms with the Model 6487, you must set up the voltage source to the desired
range, value, and current limit (see “Model 6487 voltage source operation,” page 3-12),
choose an appropriate current measurement range
(or use auto range), and enable the
ohms function. With the ohms function enabled, the Model 6487 calculates the measured
resistance from the voltage source value and the measured current (R = V/I). When setting
up the voltage source, choose as high a voltage value as possible for maximum current,
keeping in mind such factors as the power dissipation and voltage coefficient of the resis-
tance being tested.
DC and alternating voltage ohms
Model 6487 ohms measurements can be made using either the DC or alternating voltage
modes, which can be used to enhance accuracy of very high resistance measurements.
Only the DC mode is covered in this manual. See Section 3 of the Model 6487 Reference
Manual for information on the alternating voltage mode.
Procedure
WARNING Always turn off the Model 6487’s voltage source before changing volt-
age source connections to avoid a pos
sible shock hazard.
Perform the following steps to meas
ure resistance:
Step 1. Set up voltage source
Press either of the V-SOURCE adjustment keys, then use a manual RANGE key to set the
voltage source range. Set the voltage and current limit to the desired values. You can skip
the current limit prompt by pressing EXIT after adjusting the voltage.

Keithley 6487 Specifications

General

Type	Picoammeter/Voltage Source
Current Measurement Range	20 fA to 20 mA
Interfaces	GPIB, RS-232
Voltage Burden	< 200 µV
Input Impedance	>10^14 Ω
Power	100 V / 120 V / 220 V / 240 V
Basic Current Measurement Accuracy	0.4%