Novatech Instruments 408A - Page 9

9
408A Manual
mination. Set the DMM to AC Volts. Verify a read-
ing of 0.5Vrms
±
0.05Vrms. Remove the 50Ω
termination. Verify an amplitude of 1.0Vrms
±
0.1Vrms. Repeat for the I output.
6.6
Level Command Test.
Leave the output fre-
quency set to 100kHz. Send the commands “Vi
2048” and “Vq 2048”. Verify that the amplitude
on the I and Q channels decrease by half. Send the
“R” command to reset the levels before performing
the next tests.
6.7
Output Flatness Verification.
Verify that the
Sine (Q) Out is flat with frequency by performing
the following test: Connect an RF probe to the 408A
terminated with a 50Ω feedthrough termination.
Connect the output of the RF probe to the DMM, set
to DC Volts. Set the output of the 408A to 30MHz.
Select dB on the DMM.
6.8 Set the 408A to the values of Table 9. Verify
that the DMM reading is 0dB
±
3dB.
6.9 Repeat the output flatness verification test for
the Cosine (I) output.
6.10
ACMOS/TTL Verification.
Using a short
50Ω coaxial cable, connect the ACMOS/TTL output
to the recommended oscilloscope set for 50Ω termi-
nation. Using the values of Table 9, verify that the
output duty factor ranges from a minimum of 45%
high and 55% low to a maximum of 55% high and
45% low.
6.11 Set the frequency to 10kHz. Change the termi-
nation from 50Ω to 1MΩ on the oscilloscope. Verify
that the 50Ω amplitude is 1/2 that of the 1MΩ ampli-
tude,
±
10%.
6.12 This concludes the verification test of the
408A.
7.0
CALIBRATION
7.
1 The 408A has only two adjustable components:
Y2, frequency; and R52, output amplitude. Calibra-
tion should be performed only if the 408A fails the
performance test or if the unit has been repaired.
Routine adjustments are not recommended nor gen-
erally required. This procedure assumes that the
NOVATECH INSTRUMENTS
408A has failed the performance test or has been
repaired.
7.2 The adjustments shown are set to 1/2 the speci-
fication limit values.
NOTE:
Allow the 408A to warm up for at least 15 minutes
before performing any adjustments. For optimum
performance the 408A should be calibrated in its
installed environment.
7.3
Frequency Adjust, Y2.
Set the output of the
408A to 10.000000MHz. Connect the Cosine (I)
Output to your frequency counter set for 50Ω termi-
nation. Adjust Y2 using a non-metallic adjustment
tool for 10.000000MHz,
±
5Hz.
7.4
Amplitude Adjust, R52.
Set the frequency to
100kHz. Connect the Cosine (I) Output to the DMM
set for AC Volts. Do not use a 50Ω termination.
Adjust R52 for 1.00Vrms
±
0.05Vrms. This com-
pletes the calibration of the Model 408A.