GW Instek GOM-802 User Manual - Manual (Page 16)

GOM-802 DC MILLI-OHM METER
USER MANUAL
⎯ ⎯
26
7. MEASUREMENT TECHNIQUES
7-1. 4-wire measurement
(1) The 4-wire measurement can eliminate wire resistance and get accurate
resistance. Please refer to the wiring method as Figure 7-1.
Figure 7-1
Note: 1. Before testing, make sure that the KELVIN clip is well
connected with the DUT.
2. The terminals of HF (Source HI), LF (Source LO), HS (Sense
HI) and LS (Sense LO) must be connected to front panel
terminals properly.
(2) Principle
1) The traditional 2-wire measurement result combines the test lead
resistance. Please refer to Figure 7-2 for the measurement result:
2 1 r R r
I
V
+ + =
GOM-802 DC MILLI-OHM METER
USER MANUAL
⎯ ⎯
27
Figure 7-2
2) 4-wire measurement.
The 4-wire measurement takes advantage of the high input
resistance characteristic of the voltmeter that there is no voltage-
drop on r3 and r4 as no current getting through these resistances.
Therefore, the voltmeter can measure the voltage precisely on the
resistance.
The measuring result is:
Figure 7-3
(3) Zeroing
The clip of test lead includes Source+ (HF), Source- (LF), Sense+
(HS), Sense- (LS) terminals. Before zeroing test, make sure that the
clip of Sense+ is next to Sense- for accurate zeroing test. When the
quality of the wire and material can not be guaranteed, use REL
function for zeroing adjustment.
I
R
r1
r2
+
_
V VOLTMETER
CONSTANT
CURRENT
SOURCE
Ohm Meter
I
I
V
R
=
R
r3
r4
+
_
V VOLTMETER
CONSTANT
CURRENT
SOURCE
Ohm Meter
r1
r2