Performance Tests
Performance Test 3
3-37
Low Frequency Test Points (steps 1-7)
1. Connect the 75 Ω Leveling Head to the INPUT 1 connector on the AC
Measurement Standard using a precision 75 Ω feedthrough termination. (If a
Type-N feedthrough termination is not available, use a BNC 75 Ω
feedthrough termination and appropriate adapters. Ensure that BNC
connector contact resistance and repeatability does not significantly degrade
measurement uncertainty) Select INPUT 1. See Figure 3-10 for equipment
connections.
Note
Use a common mode choke to obtain satisfactory noise performance
and accurate readings. Insert the common mode choke in series
between the feedthrough termination and the AC Measurement
Standard input, with the ground applied at the choke input. Keep the
ground connection as short as possible and set the AC
Measurement Standard to Internal Guard. A common mode choke of
250 µH is usually effective. A suitable choke is 6 turns of small-
diameter coaxial cable through a TDK toroid, manufacturer’s part no.
H5C2-T28-13-16 (available as Fluke part no. 474908) Refer to the
5970A Operator Manual for additional explanation.
Note
Measurements made on the 5790A 2.2 mV range (at levels below -
42 dBm) require correction for the 2.2 mV range linearity error.
2. Set the UUT as follows:
Note
For the 96270A, ensure the Leveling Head output is selected.
Mode Leveled Sine
Frequency 1 kHz
Level +10 dBm
Output OPER
3. Allow the AC Measurement Standard to make several measurements and the
reading to settle. Convert the settled reading from V rms to dBm using the
following formula:
dBm (75 )
×
=
001.075
10
2
10
V
Log
The result must be within the tolerance listed in Table 3-17.
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