25
1159A 1GHz Active Differential Probe
Calibration Testing Procedures
Gain Accuracy Testing Procedure
This test should be preformed by qualified Agilent Service Center personnel.
1
Connect a BNC tee connector to the function generator, P/N 33120A.
2 Connect a 50-Ω cable from the BNC tee to the channel on the Infiniium
oscilloscope.
3 Set the termination on channel 1 to 50-Ω.
4 Connect the digital voltmeter (DVM) to the other side of the BNC tee.
5 Set the frequency on the function generator to 1 kHz and the amplitude
to 200 mvrms as read on the voltmeter.
6 Set the oscilloscope trigger source to channel 1.
7 Set the horizontal scale to 200 µsec/div and the vertical scale to
100 mV/div.
8 Set the oscilloscope to equivalent time sampling mode and enable
averaging with 16 averages.
9 Measure and record Vamptd _________________.
Vamptd should be -566 mV which is 2.828 x 200 mvrms.
10
Disconnect the 50-Ω cable from the oscilloscope and connect it to the
middle BNC source of the calibration test fixture, P/N 01154-63801.
11 Connect the probe under test to channel 1 on the oscilloscope and the
other end of the probe to the probe input on the middle source of the
calibration test fixture.
12 Adjust the function generator until the Vamptd reading is the same as
in step 9.
13 Record VRMS reading the digital multimeter _________________.
The reading will be slightly different from the original 200 mvrms setting if the
probe gain is not exactly 1:1.
14
Calculate the actual gain of the probe by:.
15 The percentage error of gain is: .
Note A remaining source of error is the 50-Ω termination resistor in the oscilloscope.
That error is minimized by using the same channel on the oscilloscope for all
measurements. That same error exists in the current method of measurement
since the probe is not being terminated in an exact 50-
Ω. Agilent oscilloscopes
have 1% 50-Ω termination resistors.
Gain
VRMS reading
200mvrms
------------------------------------=
Gain Error (%) Gain - 1()100×=
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