Keithley 2700 User Manual

3-26 Basic DMM Operation Model 2700 Multimeter/Switch System User’s Manual
Constant-current source method
For the 100Ω to 1MΩ ranges, the Model 2700 uses the constant-current method to measure
resistance. The Model 2700 sources a constant current (I
SOUR
) to the DUT and measures
the voltage (V
MEAS
). Resistance (R
DUT
) is then calculated (and displayed) using the
known current and measured voltage (R
DUT
= V
MEAS
/I
SOUR
).
The constant-current method is shown in Figure 3-10. The test current sourced to the DUT
depends on the selected measurement range. For example, for the 100Ω range the test
current is 1mA. Since the voltmeter of the Model 2700 has very high input impedance
(>10GΩ), virtually all the test current (1mA) flows through the DUT.
For DUT ≤1kΩ, 4-wire ohms measurements should be used as shown in Figure 3-10B. The
voltage is measured at the DUT. This eliminates IR drop in the test leads, which could be
significant when measuring low ohm DUT.
Figure 3-10
Constant-current method to measure ohms (100Ω to 1MΩ ranges)
DUT
V
ISOUR
VMEAS
Input Hi
Input Lo
2700
DUT
V
ISOUR
VMEAS
Input Hi
Input Lo
2700
Sense Hi
Sense Lo
A) 2-wire ohms (W2) measurements (100W through 1MW ranges)
R
DUT =
V
MEAS
ISOUR
RDUT =
V
MEAS
ISOUR
B) 4-wire ohms (W4) measurements (100W through 1MW ranges)

Keithley 2700 Specifications

General

Type	Digital Multimeter
Measurement Functions	DC Voltage, AC Voltage, DC Current, AC Current, Resistance, Frequency, Temperature
DC Voltage Range	100 mV to 1000 V
AC Voltage Range	100 mV to 750 V
Frequency Range	3 Hz to 500 kHz
Temperature Range	-200°C to +1372°C
Display	Vacuum Fluorescent Display
Connectivity	IEEE-488, RS-232
Channels	10
Power Supply	100V to 240V AC, 45Hz to 66Hz
DC Current Range	10 µA to 3 A
AC Current Range	10 µA to 3 A
Temperature Measurement	Thermocouple, RTD