Fluke 5520A - 3-10. AC Current Calibration

5520A
Service Manual
3-14
3-10. AC Current Calibration
Note
DC Current must be calibrated before proceeding with ac current calibration.
The ac current calibration uses a number of current shunts that require dc characterization
before they can used. DC characterization can be performed with the 5520A, as long as
you perform the entire 5520A dc current calibration first. During dc characterization, data
is obtained for each of the ac current levels required by the ac current calibration
procedure. For example, if a shunt is used for .33 mA ac and 3.3 mA ac calibrations, data
must be obtained at .33 mA dc and 3.3 mA dc.
Follow these steps to characterize the shunt:
1. Connect the test equipment as shown in Figure 3-7.
HI
LO
TRIG
GUARD
TC
20A
1000V
RMS
MAX
20V
RMS
MAX
20V
PK
MAX
1V PK
MAX
SHELLS
NOT
GROUNDED
NORMAL AUX
SCOPE
OUT
V, , ,
RTD
A, -SENSE,
AUX V
150V
PK
MAX
20V
RMS
MAX
20V PK MAX
20V PK MAX
5520A
CALIBRATOR
UUT
5790A
5790A
AC MEASUREMENT
STANDARD
1000V RMS MAX 1000V RMS MAX
3V RMS MAX
INPUT 1 INPUT 2
SHUNT
HI
LO
GUARDGROUND
SHELL FLOATING
10V PEAK
MAX
WIDEBAND
7V RMS MAX
MAX
10V PK
SHELL FLOATING
792-7004
Current
shunt
adapter
A40 shunt
Set 5790A to
external guard
yg130f.eps
Figure 3-7. Connections for Calibrating AC Current with a Fluke A40 Shunt
2. For each amplitude listed in Table 3-11, apply the equivalent +(positive) and
- (negative) dc current from the 5520A.
3. Compute the actual dc characterization value using this formula:
((+ value) - (- value))
2
The time between the dc characterization of a current shunt and its use in the calibration
process should be kept to an absolute minimum. To reduce this time, each shunt is
characterized as it is needed. As the ac current calibration procedure is performed, it must
be temporarily aborted each time a new shunt value is required. After the required shunt
is characterized, the calibration procedure is resumed at the previous point using the
newly characterized shunt.
The following example explains this procedure:
1. Perform the dc current calibration procedure.
2. Using Table 3-11, select the first required current shunt (A40-10 mA)