Using The Sg560 Differential Outputs; Performing Manual Frequency Sweeps - Ramsey Electronics SG560 User Manual

DETAILED INFORMATION

Using the SG560 Differential Outputs

Since the SG560 has a differential output, the (+) jack is 180 degrees out of phase with the
(-) jack. If the offset is at 5V the (-) jack has -2.5V of offset and the (+) jack has +2.5V in ref-
erence to the internal common point. This gives the combined total of 5V between the jacks.
If there were 100uV of noise on both the (+) and (-) terminals in reference to the internal ref-
erence, it would be common-mode noise and wouldn't be seen on the jacks. The differential
output helps to reduce any noise that a power supply or other interference may introduce into
test situations.
To use this signal generator, tie the (-) jack to ground and the (+) jack to the circuit's signal
input. This will allow for positive offsets as the display shows. If negative offsets are needed,
simply swap the (+) and (-) jacks. In this case the (+) would be connected to ground, and
the (-) the circuit input.

Performing Manual Frequency Sweeps

For testing of filters and circuit performance, it may be desirable to step the frequency and
compare the input voltage to output voltage of the circuit under test to check its frequency
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response. The SG560 is capable of sweeping in linear steps using the keypad or dial. Typically
the circuit setup would be as follows:
Do not reproduce or distribute.
TEST
DMM
SG560
CIRCUIT
-
+
( ) ( )
+
+
OUT
IN
-
-
Determine the frequency range to be tested. For example, for testing a 20kHz low pass filter,
1kHz through 100kHz would be adequate.
Set the signal generator to 0Hz by entering FREQ, 0, Hz, and then enter a level of 1V peak to
peak by entering LEVEL, 1, V. Make sure the offset is at zero volts by entering OFFSET, 0, V
and the waveform set to Sine SHAPE, ~. Next enter a reasonable step size for the frequency.
For our example we will start at 20 points. 5kHz steps are needed to reach 100kHz. To enter,
press SHIFT, FREQ, 5, kHz.
Now use the dial to step up in 5kHz steps; the sequence would be 5,10,15... 100K. For each
step make note of the meter reading and it would then be possible to enter the values into an
Excel spreadsheet and plot the result, for example.
It is preferable to use a good auto-ranging multimeter for these tests as it will save changing
settings when the filter's signal output amplitude decreases.
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