HP 3438A - AC Normal-Mode Rejection Test

Model 3438A Section IV
MULTIMETER
BOX
IIICIIII Cl I1 C lIIC11Ino 000
*FIXED RESISTORS.*.005%
MAY BE SUBSTITUTED.
3.3,-m-.eeo
I
-USE SHORT LEADS.
USE SHIELDED LEADS FOR
THE
2M AND 20M RANGE.
I
I I
Figure 4-6. Ohms Accuracy Test.
c. Set the resistive decade to zero ohms.
d. Check all ranges listed in
I-able 4-7 for the
tolerances indicated.
4-18. AC Normal-Mode Rejection Test.
4-19. The purpose of the test 1s to verify the ability ofthe
Mult~metzr to make accurate DC Voltage measurements
In the presence to AC Voltage at power line frequencies.
Definition: AC Normal-Mode Rejection is the ratio of
the peak normal-mode voltage to the resultant error in
reading.
NMRR (dB)
=
d. Disconnect the short and connect the AC
Calibrator to the Multimeter input. Adjust the
Calibrator output to 7.07 V rms
(10 V peak).
e. The Multimeter indication should not vary more
than 0.
I0 V or I0 digits peak from the indication noted in
Step c. This verifies an AC Normal-Mode Rejection of 40
d
H.
f. Repeat Steps c, d, and e for an AC Calibrator output
frequency of 50 Hz
? 0.1% as monitored by the
Electronic Counter (Period
= 19980 to 20020 ps).
4-21. AC Common Mode Rejection Ratio -
CMRR.
4-22. Phe purpose of this test is to verify the ability of the
Multimeter to make accurate AC Voltage measurements
at power
line frequencies applied simultaneously to the V
- Rsand COM terminals.
Definition: CM R R (dB) =
KMS AC Interfering Voltage
Change in ACV reading
1
Peak AC Interfering Voltage
I
4-23. An AC Calibrator and Electronic Counter are
Change in DCV reading
(i.e.. peak roll)
required for this test.
4-20. An AC Calibrator and Electronic Counter arer a. Conncet the AC Calibrator to the electronic
required for this test.
counter and adjust for a frequency of 50
HL + O.l(;h
(19.980 ps to 20,020 p s).
a. Connect the test equipment as shown in Figure 4-7.
Do not connect the Multimeter at this time.
b. Set the AC Calibrator for an output of
10 V rms.
b. Using the Electronic Counter as a monitor, adjust
c. Set the Multimeter to the ACV functionand the 2 V
the AC Calibrator frequency to 60
Hz + 0.1% (Period -
range. Connect a I K + 1% resistor between V - R and
16650 to
I6683 ps).
COM terminals at the Multimeter front panel.
c. Set the
Multirneter function to dcV (=V) and
d. Connect the AC Calibrator between the Multimeter
range to 20 V. Short the Multimeter input and note the V
- R terminal (with the I K resistor still in place) and
indication. power line ground as shown in Figure
4-8.
AC CALIBRATOR
hp 745A
I1
ELECTRONIC COUNTER
hp 5300A
MULTIMETER
C10111301I C1111I1U01IICIO
Figure 4-7. AC Normal-Mode Rejection Test.
4-5