Introduction - Ramsey Electronics SG560 User Manual

INTRODUCTION

Introduction
The SG560 is more than an audio generator. It is also a signal generator that produces AC
signals with DC coupling at the output jacks like a digital signal generator. The versatility of
the SG560 will allow you to recreate many basic signals used in testing situations.
The SG560 allows you to generate square waves, sine waves, and triangle waves of any fre-
quency from 0Hz to 5MHz in 0.1MHz steps. The frequency accuracy is tied to a crystal refer-
±
ence with an accuracy of 20ppm over its full temperature range.
You can also step the frequency at any arbitrary increment. For example a step of 37.5kHz
can be entered and the dial or shift arrows can be used to step the frequency up and down
by this amount.
The SG560 uses a robust output stage for the final driver. It is derived from DSL modems and
is essentially a high power opamp. The opamp is capable of delivering 2.5W to a load before
going into protective shutdown. It is being used in a differential fashion which means that
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any common mode noise is cancelled on the output. The output voltage can swing from 10V
peak to peak with a 5V DC offset without clipping. For a negative DC voltage output, swap
the polarity of the cables attached to the jacks.
The SG560 allows digital entry of the output level with a resolution of 10mV. For example if Do not reproduce or distribute.
you enter 5.55V, the SG560 will generate a 5.55V peak to peak waveform at the jacks. The
SG560 has an additional option which allows the user to set the output impedance. It can be
50 ohms, 25 ohms, or or 0 ohms impedance at the output jacks. With a 50 ohm output im-
½
pedance a 50 ohm load will drop the output signal level by of the value entered. With 0
ohms a 50 ohm load will not drop the level at all. The 25 ohm output setting can help when
driving a capacitive load; the 0 ohm setting should never be used with this type of load.
A DC offset may be entered; this is added (or subtracted if the jack connections are reversed)
to the AC signal. Rather than the output AC waveform being centered on 0VDC, a set DC volt-
age can be added to your signal. This allows the performance of tests that are not possible
with a basic audio signal generator. For example, a small circuit can be powered by the DC
offset as long as it requires less than 2.5W of power, and AC signals can be used to check for
noise or EMI immunity. The DC offset can also be used to recreate digital signals in the
square wave mode. For example, to create TTL square waves, enter 5V for the level, and 2.5V
for the offset. This will create the 5V (digital '1') and the 0V (digital '0') levels needed for test-
ing and clocking digital circuits. With a signal range of up to 10V peak to peak and 5V of off-
set, even old 4000 series CMOS signal levels can be recreated! While this logic family is not in
wide use, it may be useful for testing older circuits.Both the level and offset fields can be
stepped in arbitrary amounts and have a monotonic resolution of 10mV.
Additionally the SG560 contains 6 non-volatile memories which save the full system settings:
frequency, level, shape, and offset. This allows you to frequency hop or use the memories to
"script" repair, testing, and alignment procedures. The SG560 can be run from a broad spec-
trum of power sources; this allows for portable battery operation if desired, using the proper
precautions.
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