The Wavetek Model FG3B Sweep/Function Generator is a versatile instrument designed for generating various waveforms and performing sweep and modulation functions. It is suitable for a wide range of applications including vibration testing, servo system evaluation, general-purpose audio response testing, and ultrasound applications.

Function Description:

The FG3B is a stable, low-distortion instrument capable of generating signals in the 0.2 Hz to 2.0 MHz frequency range. Its core functions include:

Waveform Generation: Produces low-distortion sine, triangle, square, and ramp signals.
Frequency Control: Offers signal outputs in seven decade increments from 0.2 Hz to 2.0 MHz, with a frequency control knob for precise setting.
Sweep Capabilities: Features linear or logarithmic sweep modes with adjustable sweep time and sweep width. This simplifies finding resonant points in speakers, filters, and structures, allowing for automatic display of responses on an oscilloscope.
Modulation: Provides AM or FM capability with internal (400 Hz) or external modulation control.
Duty Cycle Control: Allows adjustment of the duty cycle from 50% (1:1) to approximately 10% (10:1), with an inversion feature. This affects both the main output and the TTL/CMOS output.
DC Offset: An adjustable positive or negative DC offset voltage can be applied to the main output signal.
External VCF (Voltage Controlled Frequency): Allows external DC voltage to control the function generator's frequency over a 3-decade range. A positive voltage input decreases the output frequency, while a negative input increases it.
Built-in Frequency Counter: A 5-digit LED display shows the frequency value. The counter can measure and display internal signals up to 2 MHz and external signals up to 100 MHz. It has selectable gate times from 10 seconds to 0.01 seconds for varying resolution.
Outputs: Includes a main signal 50 ohm output with DC offset adjustment and 20 dB attenuation, and a second output for TTL or adjustable CMOS pulses.

Important Technical Specifications:

Output Waveforms: Sine, triangle, square (from OUTPUT connector); Square (from TTL/CMOS connector).
Amplitude (OUTPUT connector): >20V P-P open circuit; >10V P-P into 50Ω load.
Amplitude (TTL/CMOS connector): TTL: >3V open circuit; CMOS: 4 to 14.5V, adjustable.
Impedance (OUTPUT connector): 50Ω ± 6%.
Attenuator (OUTPUT connector): -20dB ± 1dB at 1kHz.
DC Offset (OUTPUT connector): <-10V to >+10V (no load); <-5V to >+5V (50Ω load).
Duty Cycle: 1:1 to 10:1 minimum, variable.
Display: 5-digit LED display for frequency, 4 LED indicators (Gate, Over, kHz, MHz).
Frequency Range: 0.2Hz to 2.0MHz in 7 ranges.
Sine Wave Distortion: <1%, 0.2Hz to 200kHz.
Sine Wave Flatness: <0.2dB, 0.2Hz to 100kHz; <1dB, 100kHz to 2MHz.
Triangle Wave Linearity: >98%, 0.2Hz to 100kHz; >95%, 100kHz to 2MHz.
Square Wave Symmetry: <2%, 0.2Hz to 100kHz.
Square Wave Rise/Fall Time: <120ns.
CMOS Output Rise/Fall Time: <120ns.
TTL Output Rise/Fall Time: <25ns.
VCF Input: 0 to 10V (±1V) for 1000:1 frequency ratio; Input Impedance ≥ 10kΩ.
Frequency Counter Ranges: Internal: 0.2Hz to 2MHz; External: 5Hz to 10MHz, 5MHz to 100MHz (back panel switch selected).
Frequency Counter Accuracy: 10 PPM ± 1 count at 23°C.
Sweep Time: 0.5 sec. to 30 sec., adjustable.
Sweep Type: Linear or Logarithmic, switch selectable.
Amplitude Modulation Depth: 0-100%, adjustable.
AM Modulation Freq.: 400Hz internal, DC-1MHz external.
AM Carrier BW: 100Hz to 2MHz (-3dB).
AM Ext. Sensitivity: <10V P-P for 100% modulation.
Frequency Modulation Deviation: 0 to ± 5%.
FM Modulation Freq.: 400Hz internal, DC-20kHz external.
FM Ext. Sensitivity: <10V P-P for ± 5% deviation.
Power Source: North American: 117V, 60Hz; Europe, UK: 234V, 50Hz.
Dimensions: 22.8(W) x 8(H) x 32.9(D) cm (9(W) x 3.13(H) x 13(D) inches) exclusive of handle.
Weight: 2.0 kg (4.5 pounds) typical.

Usage Features:

Preliminary Checkout: Before operation, users should verify line voltage compatibility, connect the power cord, and push the PWR switch. Controls should be preset to their default positions (all pushed in, non-power buttons released, AMPL and OFFSET midposition, DUTY at CAL, FREQUENCY fully counterclockwise).
Square, Triangle, or Sine Wave Output: Select the desired function, push the appropriate Range button for the frequency decade, and rotate the FREQUENCY knob to set the exact frequency. Amplitude and DC offset can be adjusted via their respective knobs. The TTL/CMOS output provides a simultaneous logic signal, fixed at >3V for TTL or adjustable 5-15V for CMOS.
Pulse/Ramp Output: Similar to waveform output, but selecting the square wave function allows for pulse/ramp generation. The DUTY knob varies the duty cycle, and pulling it inverts it.
VCF Operation: Enable VCF mode by ensuring the SWEEP WIDTH knob is pushed in. Connect an external DC control voltage to the VCF/MOD IN connector to adjust the output frequency.
External Counter Operation: To measure external signals, push the CNTR INP switch in, select the appropriate back panel switch (10MHz or 100MHz), connect the signal to EXT CNTR, and press a gate time button. For accuracy, a 60-second wait is recommended for the 10-second gate time.
Auto Sweep Operation: Pull the FREQUENCY knob for sweep mode. Set the maximum desired frequency, adjust AMPL and TTL/CMOS output levels. For log-type sweep, pull the SWEEP TIME control; otherwise, leave it pushed in for linear sweep. Adjust SWEEP WIDTH to cover the desired frequency range and SWEEP TIME for the sweep rate.
AM/FM Modulation Operation: Pull the SWEEP WIDTH knob out to turn on modulation. Pull the MODULATION CARRIER knob out for FM, or leave it pushed in for AM. For external modulation, push the MOD button in; otherwise, the internal 400Hz signal is used. Adjust the MODULATION CARRIER knob for the desired modulation level.
Amplifier Response Testing: The FG3B is ideal for sweep testing audio power amplifiers. Connect the generator to both the amplifier input and oscilloscope Channel 1. Terminate the amplifier output with a load resistor (e.g., 8 ohm, 100 watt non-inductive) and connect it to oscilloscope Channel 2. Set the generator for a 20Hz to 20kHz linear sweep with sine wave output, and the output level to half the amplifier's rated power. Observe output signal variations during the sweep. An oscilloscope with ADD mode and INVERT switch can simplify comparison by displaying the difference between input and output levels.

Maintenance Features:

Safety Precautions: Users are warned against operating the instrument with the case open, ungrounded, or allowing water inside. Voltage input limits for external counter and VCF/modulation connectors must be observed. The instrument should not be placed on high-temperature equipment and should be operated within 0°C to 50°C.
Troubleshooting: A dedicated section provides guidance for common issues such as an inoperative instrument (check power, fuse), counter not reading frequency (check CNTR INP button, gate time), or excessive output distortion (use 50 ohm termination, reduce amplitude).
Fuse Replacement: Instructions are provided for safely replacing the internal fuse, including disconnecting AC power and using a Phillips screwdriver to remove the bottom half case.
Line Voltage Changes: The instrument is hard-soldered internally for a specific line voltage. Instructions detail how to change the voltage selection (e.g., from 117VAC to 234VAC) by removing or adding jumpers on the power transformer board and replacing the fuse with the correct rating (0.5A, 3AG for 117V; 0.25A, 3AG for 234V). A new label should be placed over the rear panel to indicate the changed voltage.
Factory Service and Repair: Wavetek offers factory service with 24-hour turnaround time for repairs in the United States. Instruments returned for service should include company name, user name, address, phone number, proof of purchase (for warranty repairs), any test leads used, and a written description of the problem. Shipping addresses for U.S.A. and U.K. are provided.

Wavetek FG3B - Page 44

Table of Contents

Related product manuals