B&K Precision 4078 - Manual - Manual (Page 18)

generator setting, to the generator. This connector is also used when using an external signal to generate
FSK under modulation menu. (See section 3.6.8 for details)
3. Marker Out - Use this connector to output a positive TTL pulse in Arbitrary waveform mode. The
Marker position and width can be programmed at any desired Arbitrary locations. (See section 3.6.3 for
details)
4. Sync Out - Use this connector to generate a positive TTL sync pulse output at each waveform cycle.
5. Ref In/Out - Use this connector to input a 10 MHz TTL signal to be used as a reference clock for the unit
signal generation. A 10MHz TTL level signal is available for synchronization of external units, when not
in External Reference mode.
6. RS-232 Port - Used to connect to PC via serial cable for RS-232 serial interface and programming.
7. AC Power Connector - Used to connect power cable to AC line source.
8. Fuse Box - Fuse compartment to check or replace fuse.
9. Rear Fan - Rear fan for internal cooling and ventilation. Do not block this area and be sure to leave
enough room for air to exhaust.
10. GPIB Port - (Optional) For connecting to PC using GPIB interface.
3.5 Output connectors
The waveform generator output circuits is protected against short circuit or nominal accidental voltages applied to the
main output connector . It operate as a 50 ohm voltage source working into a 50 ohms load. At higher frequencies,
non-terminated or improperly terminated output causes aberrations on the output waveform. In addition, loads less than
50 ohms reduce the waveform amplitude, while loads more than 50 ohms increase waveform amplitude.
Excessive distortion or aberrations caused by improper termination are less noticeable at lower frequencies, especially
with sine and triangle waveforms. To ensure waveform integrity, follow these precautions:
1. Use good quality 50 ohms coaxial cables and connectors.
2. Make all connections tight and as short as possible.
3. Use good quality attenuators if it is necessary to reduce waveform amplitudes applied to sensitive circuits.
4. Use termination or impedance-matching devices to avoid reflections.
5. Ensure that attenuators and terminations have adequate power handling capabilities.
If there is a DC voltage across the output load, use a coupling capacitor in series with the load. The time constant of the
coupling capacitor and load must be long enough to maintain pulse flatness.
Impedance Matching
If the waveform generator is driving a high impedance, such as the 1 M
Ω input impedance (paralleled by a stated
capacitance) of an oscilloscope vertical input, connect the transmission line to a 50
Ω attenuator, a 50 Ω termination
and to the oscilloscope input. The attenuator isolates the input capacitance of the device and terminates the
waveform generator properly.
3.6 MENU Keys
These keys select the main menus for displaying or changing a parameter, function or mode. Below is the hierarchy
and selections of the menu tree.
MENU TREE
- SINE
o FREQ
o AMPL | OFST
o INTREF | EXTREF
- RAMP