OPERATING INSTRUCTIONS
19
OUTPUT PROTECTION CONSIDERATIONS
Use care when connecting the function generator output to a
signal injection point. Excessive voltage at the point of signal
injection of the function generator can cause internal damage.
Under normal operation, the generator output should never be
connected to an external voltage other than low dc values that can
be matched with the
DC OFFSET
control. The Model 4040 is
overload protected so that shorting the output, even continuously,
will not cause damage. A fuse has been added in series with the
OUTPUT
jack to help protect the instrument from damage by
connection to excessive external voltage.
Damage of this type usually occurs by accidentally connecting
the output of the function generator to a voltage in the equipment
under test. The following protective measures are strongly
recommended:
The user should understand the equipment under test well
enough to identify valid signal injection points (e.g., the base of a
transistor, a logic input of a gate, etc.). The voltage at valid signal
injection points is rarely high enough to damage the instrument.
If in doubt about the safety of a signal injection point, measure
the voltage present at the intended point of signal injection before
connecting the function generator output to that point.
When applying the main output of the function generator to a
circuit point containing a dc level, adjust the DC OFFSET control
so that the dc level at the main output matches the circuit voltage.
Connect the
TTL
output only to TTL-level circuits. Connect the
CMOS
output only to CMOS circuits. Measure the Vcc of the
Figure 7. Circuit for Protection of TTL Output.
circuit under test and adjust the
CMOS LEVEL
control
as instructed in the manual.
When the function generator is used by students or other
inexperienced users, the circuit shown in Fig. 7 could be
added into your TTL output probe or test clip set. It will
protect the TTL output of the generator against external
voltages up to ± 20 volts.
FUNCTION GENERATOR APPLICATIONS
GUIDEBOOK
B+K Precision
offers a “Guidebook to Function
Generators” which describes numerous applications for
this instrument, including hook-up details. It also includes
a glossary of function generator terminology and an
explanation of function generator circuit operation. It
maybe downloaded for free off our website at
www.bkprecision.com.
