Gamry Instruments Reference 30k Booster, Operator'S Manual

Page: 40 / 55

Suggestions for Cell Connection – 4-Terminal Cell Connections
40

The software opens a message box telling you how the connections should be made based upon your
expected maximum voltage.
The allowed voltage on the Counter Sense (Orange) lead is

30 volts. DC accuracy of the voltage measurement
is reduced in high-voltage mode.
When you are making 4-terminal measurements on a two-terminal device, one current-carrying and one sense
lead connects to each terminal on the device. Ideally, the sense lead contacts the terminal independently of the
current-carrying contact.
The sense lead should be connected as close to the device as possible.
Figure 5-1 shows a half of a reasonably good 4-terminal connection with two alligator clips to a battery
terminal. Each clip contacts the terminal independently and the sense clip is closest to the battery. The sense
lead “sees” voltage drop caused by current through the battery terminal. The copper terminal’s resistance is
quite low, so voltage errors are small.
The resistance of this “good 4-terminal” battery contact was measured using a Gamry EIS system. The
measured resistance was 0.3 m
Ω .
Figure 5-1
Good 4-Terminal Clip Placement on a Battery Terminal
Figure 5-2 shows half of a very poor 4-terminal connection with two alligator clips to the same battery terminal.
The sense lead “sees” voltage drop caused by the resistance both in the current-carrying clip, and the resistance
of the clip-to-terminal contact.
Battery
Current-carrying clip
Sense clip