B&K Precision 4011A - Manual - Manual (Page 11)

11
OPERATING INSTRUCTIONS
7. A superimposed DC component can be added to the output signal
by engaging the DC OFFSET switch (12) to enable operation of
the DC OFFSET control (5). Rotation of this control adds a
positive or negative DC component to the output signal. The DC
component introduced is independent of the OUTPUT LEVEL
control and can be varied by ±10 volts open circuited or ±5 volts
into 50Ω. The DC Offset does not affect the TTL/CMOS output
jack. The effect of DC OFFSET is shown in Fig. 3.
CONSIDERATIONS
1. l. Counterclockwise rotation of the COARSE frequency control
decreases the output frequency to approximately one-tenth of the
maximum for the range selected (10:1). For example, if the 50K
range is selected and the COARSE frequency control is set to
full counterclockwise, the output frequency is approximately
5kHz.
2. It is advisable to set the FINE frequency control to the
approximate center of its rotation before setting the COARSE
frequency control. This assures that the FINE control will not
reach its limit while trying to finalize the frequency setting.
3. The FINE frequency control provides approximately ±5%
frequency deviation from the COARSE control setting. This
provides vernier adjustment to easily set the frequency to a
precise value.
4. . When the 5Hz range is selected, the gate time is 10 seconds and
the display is updated once every 10 seconds. The result of a
frequency change will not be displayed until 10 seconds later.
Adjust the frequency in progressively smaller steps, waiting for
the display to update until the desired frequency is obtained.
5. When outputting square waves or when using the TTL output,
terminate the cable into 50Ω to minimize ringing. Also, keep
cables as short as possible.
Figure 3. Use of DC OFFSET Control
6. Remember that the output signal swing of the
generator is limited to ±10 volts open circuited or ±5
volts into 50Ω, and applies to the combined peak-to-
peak signal and DC offset. Clipping occurs slightly
above these levels. Fig. 3 illustrates the various
operating conditions encountered when using the DC
offset. If the desired output signal is large or if a large
DC offset is required, an oscilloscope should be used
to make sure that the desired signal is obtained without
undesirable clipping.