Front Panel Operation
3-34
Because of accuracy considerations, in-circuit current read-
ings are limited to traces with a resistance of 1mΩ to 10Ω. If
either of these limits is exceeded in the resistance calcula-
tion, the in-circuit current cannot be calculated. The bottom
line of the front panel display will show and update the trace
resistance.
A procedure to measure in-circuit current follows:
1. Select the in-circuit current measurement mode from the
CONFIGURE DCI menu and place the instrument in
the DCI function. Note that the 4W annunciator lights to
indicate this is a 4-wire measurement.
2. Connect a set of Kelvin test probes, such as Keithley
Model 5805 or 5806, to the Model 2001 INPUT HI and
LO terminals and SENSE HI and LO terminals.
3. For R
TRACE
<50mΩ, or where the conductors are physi-
cally hot, rel out (zero correct) any thermal offsets that
are present before measuring in-circuit current. With
power to the test circuit removed, place the probes on
the desired trace and enable rel from the DCI function.
4. Turn on the power to the test circuit and read the in-cir-
cuit current calculation. The speed of this measurement
is four readings per second at 1PLC. Its range is fixed at
12A. The default filter for in-circuit current is a moving
average of ten readings. Additional filtering may be
needed at low voltage levels.
COUPLING
This parameter selects the input coupling for the ACI func-
tion. When AC coupling is selected, a DC blocking capacitor
is placed in series with the AC measurement circuit. (Note
that the current shunt resistors are always DC coupled to the
inputs.) This removes the DC component from the RMS and
average ACI measurement.
When AC+DC coupling is selected, the blocking capacitor is
removed. Subsequent RMS or average ACI measurements
will reflect both the AC and DC components of the signal.
You can set the ACI coupling as follows:
1. From the CONFIGURE ACI menu, select COUPLING
and press ENTER. The following menu is displayed:
SET AC COUPLING
AC AC+DC
2. Highlight the desired coupling and press ENTER.
Note that the coupling settings for ACI and ACV are discrete.
Thus, setting the coupling of ACI has no effect on the cou-
pling of ACV.
AC-TYPE
This parameter selects the measurement type for the ACI
function. The Model 2001 directly measures RMS and aver-
age AC current. You can program the ACI type parameter as
follows:
1. From the CONFIGURE ACI menu, select AC-TYPE
and press ENTER. The following menu is displayed:
SET ACI MEASUREMENT
RMS AVERAGE
2. Highlight the desired measurement type and press EN-
TER.
RMS: With this parameter selected, the instrument performs
RMS AC current measurements.
AVERAGE: When this item is selected, the signal path in
the instrument bypasses the RMS converter, so the average
ACI measurement is just the filtered output of a full wave
rectifier.
Multiple displays
The multiple displays for AC current that show multiple
functions are shown in Figure 3-13. There are no multifunc-
tion displays for DC current.
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