Front Panel Operation
2-26
IN-CIRCUIT:
In-circuit current is a calculation based on a
4-wire resistance measurement and a voltage measurement.
It is similar to an offset-compensated ohms measurement.
Table 2-15
DCI and ACI auto resolution
Measurement
function and type Integration time Resolution
DC current 0.01 to <0.02 PLC
0.02 to <0.20 PLC
0.20 to <2.00 PLC
2.00 to 50 PLC
4.5d
5.5d
6.5d
7.5d
DC in-circuit current Not used 5.5d
RMS, average 0.01 to <0.02 PLC
0.02 to <10.00 PLC
10.00 to 50 PLC
4.5d
5.5d
6.5d
Notes:
1. For normal DC current, if the resolution is AUTO and the integration
time is SET-BY-RSLN, the resolution will be 6.5 digits and the integra-
tion time 1.0 PLC.
2. For DC in-circuit current, the integration time setting is ignored.
3. For AC current, if the resolution is AUTO and the integration time is
SET-BY-RSLN, the resolution will be 5.5 digits and the integration
time 1.0 PLC.
Figure 2-7
DC in-circuit current measurements
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FREQ TEMP
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INFO LOCAL CHAN SCAN CONFIG MENU EXIT ENTER
RANGE
AUTO
FILTER MATH
RANGE
2002 MULTIMETER
SENSE
Ω 4 WIRE
HI
INPUT
LO
INPUTS
CAL
500V
PEAK
F
R
FRONT/REAR
2A 250V
AMPS
350V
PEAK
1100V
PEAK
Model 2002
Circuit
Under Test
Caution : Maximum Input = +200mV on
(I
IN - CKT
+ I
SOURCE
) • R
TRACE
, where
I
SOURCE
= 10mA.
+00.207 ADC ICkt
Trace resistance: 1.0000Ω
Y
Y
x
Note: The distance
"X" must be greater
than 10 times the
distance "Y" or
additional errors will
be introduced.
The current in a low resistance conductor (e.g., a printed
circuit trace) can be measured without breaking the current
path. The Model 2002 can do this with a pair of Kelvin test
probes across the conductor. See Figure 2-7. The method
follows:
1. Using one set of the Kelvin probe tips, the instrument
sources a known current (I
SOURCE
) through the conductor
and simultaneously measures the resulting voltage
(V
MEAS1
) with the other set of probe tips:
or
2. The instrument then measures the voltage (V
MEAS2
)
across the conductor without sourcing an additional
current:
or
V
MEAS1
I
IN-CKT
I
SOURCE
+()R
TRACE
=
R
TRACE
V
MEAS1
I
IN-CKT
I
SOURCE
+()
-------------------------------------------------=
V
MEAS2
I
IN-CKT
()R
TRACE
=
R
TRACE
V
MEAS2
I
IN-CKT
()
----------------------=
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