12
DDS9m Manual
6.4 Sine Out Amplitude Verification. Set the fre-
quency of the DDS9m to 10MHz. Connect the
DDS9m to the oscilloscope set for 50
Ω
termination.
Set the oscilloscope to measure to amplitude using
at least 16 averages. Verify a reading of 1Vpp
±
0.25Vpp. Repeat for the other outputs.
6.5 Level Command Test. Leave the output fre-
quency set to 10MHz. Send the commands
“Vn
512”
to each channel, where
‘n’
is your selected
channel number. Verify that the amplitude on each
channel decreases by one-half. Send the
“R”
com-
mand to reset the levels before performing the next
tests.
6.6 Output Flatness Verification. Verify that the
outputs are flat with frequency by performing the
following test: Connect the DDS9m to the oscillo-
scope set for 50
Ω
termination. Use the same settings
as Sine Out Amplitude Verification. Note the volt-
age reading.
6.7 Set the DDS9m to the values of Table 4. Verify
that the oscilloscope amplitude reading remains
within
±
3dB (1.414 to 0.707) of the value noted in
the previous paragraph. (limit upper frequency
to150MHz)
6.8 Repeat the output flatness verification test for
each output.
6.9 External Clock Input Verification. Set the fre-
quency output to 10.000MHz by sending the com-
mand
“F0 10.7374182”
(scaled per section
4.0). Connect a 400MHz external clock source via a
short coaxial cable to the external clock MCX. Send
the command
“Kp 01”
. Send the command
“C
e”
to select the external clock input.
6.10 Verify an output of 10.0000000MHz,
±
0.1Hz.
You must account for any frequency errors in your
external clock source.
NOVATECH INSTRUMENTS
6.11 Return the DDS9m to normal operation and
default values by sending the
“CLR”
command.
6.12 This concludes the verification test of the
DDS9m.
7.0
CALIBRATION
7.1 The DDS9m has two adjustable components:
Y2, frequency, and R22, output amplitude. Calibra-
tion should be performed only if the DDS9m 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
DDS9m has failed the performance test or has been
repaired.
7.2 Before proceeding with calibration, send the
‘CLR’
command to set the DDS9m to factory
default values.
WARNING:
Calibration should be performed only by qualified
personnel. The on-board components are static
sensitive.
7.3 The adjustments shown are set to 1/2 the speci-
fication values.
NOTE:
Allow the DDS9m to warm up for at least 15 minutes
before performing any adjustments. For optimum
performance the DDS9m should be calibrated in an
environment similar to its installation.
7.4 Frequency Adjust, Y2. Set the output of the
DDS9m to 10.0000000MHz using the command
“F0 10.0000000”
. Connect output of channel 0
to your frequency counter set for 50
Ω
termination.
Adjust Y2 using a non-metallic adjustment tool for
10.000000MHz,
±
7.5Hz.
7.5 Amplitude Adjust, R22. Connect the output of
channel 0 to the oscilloscope set to measure ampli-
tude, with a minimum of 16 averages. Set for 50
Ω
termination. Set the output to 35MHz by sending the
command
“F0 35.0000000”.
Adjust R22 for
1.00Vpp
±
0.05Vpp. This completes the calibration
of the Model DDS9m.
30 MHz
±
45 Hz
±
1 LSD
50 MHz
±
75 Hz
±
1 LSD
100 MHz
±
150 Hz
±
1 LSD
170 MHz
±
255 Hz
±
1 LSD
Table 4: Frequency Test Points
Frequency
Tolerance
