Keithley 2700 User Manual

Model 2700 Multimeter/Switch System User’s Manual Measurement Considerations E-7
path such as power line ground. As shown in Figure E-2, the resulting ground loop causes
current to flow through the instrument LO signal leads and then back through power line
ground. This circulating current develops a small but undesirable voltage between the LO
terminals of the two instruments. This voltage will be added to the source voltage,
affecting the accuracy of the measurement.
Figure E-2
Power line ground loops
Figure E-3 shows how to connect several instruments together to eliminate this type of
ground loop problem. Here, only one instrument is connected to power line ground.
Ground loops are not normally a problem with instruments like the Model 2700 that have
isolated LO terminals. However, all instruments in the test setup may not be designed in
this manner. When in doubt, consult the manual for all instrumentation in the test setup.
Figure E-3)
Eliminating ground loops
Signal Leads
Instrument 1
Power Line Ground
Ground
Loop
Current
Instrument 2 Instrument 3
Instrument 1
Power Line Ground
Instrument 2 Instrument 3

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