User manual

2400 Series SourceMeter
®
User’s Manual Source-Measure Concepts 6-29
If you want to measure the resistance of a single resistor in the network, you must
use the ohms guard configuration. Figure 6-18B shows how to measure the resis-
tance of R1. Since the voltage on either side of R2 is the same, no current can
flow through it. Thus, all the programmed current (I
M
) from the SourceMeter will
flow through R1. The voltage across R1 is then measured, and an accurate resis-
tance measurement is calculated, in this case 20kΩ.
NOTE Guard current (I
G
) must not exceed 50mA. If it does, the guard voltage
drops lower than the output voltage allowing leakage current. Thus, the
guarded ohms measurement becomes corrupted.