B&K Precision 4079 - Manual - Manual (Page 19)

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position and width can be programmed at any desired Arbitrary locations. (See section 3.6.3 for details)
6. 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.
7. Trig In - Use this connector to apply an external trigger or gate signal, depending on the waveform generator
setting, to the generator. This connector is also used when using an external signal to generate FSK under
modulation menu. Maximum input is ± 15 V. (See section 3.6.8 for details)
8. CH2 I/O - These are the same inputs/outputs as 1, 3, 5, and 7 and are dedicated for channel two only.
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. Fuse Box - Fuse compartment to check or replace fuse.
11. AC Power Connector - Used to connect power cable to AC line source.
12. Earth GND - This screw is the earth ground that is tied to the chassis.
13. GPIB Port - This is a standard GPIB port for remote interface.
14. RS-232 Port - This is a standard RS-232 port used for remote interface. Null modem or cross serial cable is
required to communicate with a PC via this port.
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 MΩ 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
- PARAM
o FREQ | RATE