Operator`s manual

39 Signametrics
1 uA
Ω 10 00 Ω 3.3 MΩ 1 Ω 1 10 Ω
33 MΩ
100 nA
0 Ω 10 kΩ 100 10 0 Ω 1 Ω
330 MΩ
10 nA
kΩ 1 0 kΩ 100 10 kΩ 1 kΩ
4.3.7 Gu rdi g Hi h Val ance Measurements (SM2064)
ing high value re ors us he 2- quire special at he high impedances
d leakage could be very significant. To improve this type of
easurement it is important to use good quality shielded cables with a low leakage dielectric. Even with a good
ror
ce,
L
ead, for leakage
urrent to develop. Provided there was a way to eliminate this voltage, leakage would have been eliminated.
a n g ue Resist
Measur sist ing t Wire function re tention. Due to t
involved during such measurements, noise pickup an
m
dielectric, if a significant length is involved, an error would result due to leakage. Figure 4.8 exemplifies this er
source. It is important to emphasize that in addition to the finite leakage associated with the distributed resistan
, there must also be a voltage present between the two conductors, the shield and the center l
R
c
Figure 4-8. Depiction of the error caused the cable leakage, R
L
.
prov s an ctive guard signa onnected to the s nd prevent the leakage caused by
ric’s fin e res nce. W the sh in Figure 4-9, there is 0V
the shiel d t igh sense wire, no current flows t h R
.
The SM2064 ide a l that can be c hield a
the dielect it ista ith ield voltage guarded with Vx, as indicated
between d an he h and therefore hroug
L
Figure 4-9. Guarding improves accuracy in 2-W ire measurement while testing high value resistors.
est, and measuring the
urrent through it. Three ranges are provided, 240nA, 2.4uA and 24uA. The voltage can be set between -10V and
+10V. See Figures 4-10 for connection. The DC voltage at which leakage is measured is set using
4.4 Leakage Measurements (SM2064)
The SM2064 measures leakage currents by applying a DC voltage across the device under t
c