Basic Instrumentation And Measurement - Function Generator

The Function Generator series are stable low distortion instruments, which generate signals in the frequency range up to 5MHz. Typical applications include a wide range of audio response testing application, vibration testing, servo system evaluation, ultra sound application and etc.

These instruments include the following features: logarithmic and linear sweep capabilities, together with a built in frequency counter. The sweep capability simplifies the task of finding resonant points of speakers, filter networks and other networks/structures. An oscilloscope may be connected to this instrument for the response to be displayed. The counter can be switched to measure and display the frequency of an external signal up to 150MHz.

Panel Control And Indicator

Front Panel

Rear Panel

FUNCTION DESCRIPTION

FRONT PANEL

1. Power Switch : Connect the AC power, then press power switch.
2. a) Gate Time Indicator : Press the power switch, Gate time indicator will start to flash (the gate of internal counter is 0.01 second)

2.   b) Gate Time Selector : Press the key to change gate time when use external           counter mode. The change order is according to 0.01s, 0.1s, 1s, 10s cycle by            pressing these keys.

3. Over Indicator : In the external counter mode, the indicator is illuminated when the output frequency is greater than the range selected.
4. Counter Display : Shows the external frequency by 6 x 0.3” green display, and shows the internal frequency by 5 x 0.3 green display.
5. Frequency Indicator : Indicate the current frequency value.
6. Gate Time Indicator : Indicate the current Gate time (external, counter mode use only)
7. Frequency Range Selector : To select the required frequency range by pressing the relevant push button on the panel as shown in Table 1 and Table 2.

Table 1 (for GFG-8215A/8216A/8217A/8219A)

Push bottom	1	10	100	1k	10k	100k	1M
Frequency Range	0.3Hz / 3Hz	3Hz / 30Hz	30Hz / 300Hz	300Hz / 3kHz	3kHz / 30kHz	30kHz / 300kHz	300kHz / 3MHz

 

Table 2 (for GFG-8250A/8255A)

Push bottom	1	10	100	1k	10k	100k	1M
Frequency Range	0.5Hz / 5Hz	5Hz / 50Hz	50Hz / 500Hz	500Hz / 5kHz	5kHz / 50kHz	50kHz / 500kHz	500kHz / 5MHz

 

8. Function Selector : Press one of the three push buttons to select the desired output waveform.
9. Duty Function : Pull out and rotate the knob to adjust the duty cycle of the waveform.
10. TTL/CMOS Selector : When push in the knob. The BNC terminal of (20) will output a TTL compatible waveform. If pull out and rotate the knob can adjust the CMOS compatible output (5-15 Vpp) from the output of BNC (20)
11. DC Offset Control : Pull out the knob to select any DC level of the waveform between ± 10V, turn clockwise to set a positive DC level waveform and invert for a negative DC level waveform.
12. Output Amplitude Control with Attenuation Operation : Turn clockwise for MAX, output and invert for a –20dB output. Pull the knob out for and additional 20dB output attenuation.

12. a) 20dB Attenuation : Press the knob to adjust a –20dB output.
13. MANU/SWEEP Selector and Frequency Adjustment (sweep On/Off) : Press and turn clockwise the knob for MAX frequency and invert for MIN frequency. (Keep the pointer within the scale range on the panel) Pull out the knob to start the auto sweep operation; the upper frequency limit is determined by the knob position.
14. Sweep Time Control and LIN/LOG Selector : I) Rotate the knob clockwise to adjust sweep time for MAX, or invert for MIN. II) To proceed Linear sweep mode by pushing in the knob, or select LOG sweep mode by pulling out the knob.
15. Control MOD ON/OFF Selector : Pull out the knob, the output can be modulated by internal 400Hz. Sine wave or an external signal via VCF/MOD in connector.
16. Sweep Width & Modulation Carrier & AM/FM Selector & FM Selector : I) Sweep width can be controlled from 0 to 1000 times. II) To adjust modulation ratio by turning the knob clockwise for MAX, or invert for MIN. III) Press the knob to get AM function or pull it out for FM function
17. INT/EXT MOD selector : When press the button once, the indicator will lighten, then the EXT MOD has been selected.

 REAR PANEL

18. INT/EXT Counter Selector : Select internal counter mode (count the frequency of model) or select EXT counter mode for an independent counter (input signal from BNC(19)).
19. EXT. counter Input Terminal: Accepts external signals for measurement.
20. TTL/CMOS Output Terminal : TTL/CMOS compatible signal output.
21. VCF/MOD Input Terminal : Used to connect the input voltage required to perform the “voltage control frequency” operation or the EXT modulation operation.
22. Main Output Terminal : Main signal output.
23. GCV Output : This is DC voltage output and its voltage amount will follow the change of Frequency.
24. Power Switch : 115V and 230 V selectable.

USAGE DESCRIPTION

First –step check:

1. Ensure that the voltage of the main supply is compatible with this instrument. The label on the rear panel states the required AC voltage.
2. Connect the instrument to the main supply using the power cord supplied.
3. Press PWR switch (1) and ensure all the rotary controls are pushed in, then rotate AMPL (12) knob to make the indication point up forward.
4. Rotate the FREQ (13) control fully anticlockwise.

 Triangle, square and sine wave.

1. First select Function (8), and select Range (7), rotate FREQ (13), to the set required frequency. (read out from display windows)
2. At this moment, connect Output (22), to oscilloscope for observing output signal, or connect to other experiment circuit.
3. Rotate AMPL (12) again to control waveform amplitude.
4. If attenuation output signal is required, pull out AMPL (12) knob to obtain 20dB attenuation or press (12a) knob for additional 20 dB attenuation.
5. The phase-relation of Output Waveform shown in Figure 1 as below: 

Pulse wave generation

1. First press the key (         ) of Function (8) ; then select Range (7) and rotate FREQ (13), to set required frequency range.
2. Connect output-terminal (22) to oscilloscope for observing output signal.
3. pull out and rotate Duty (9) to adjust the width of pulse waveform.
4. Adjust AMPL (12) knob to control pulse amplitude.
5. Pull out AMPL (12) knob to get 20dB attenuation of output.

 

Ramp wave generation

1. First press the key (          ) of Function (8), then select Range (7) rotate FREQ (13) switch to set required frequency range.
2. Connect output-terminal (22) to oscilloscope foe observing output signal.
3. Pull out and rotate DUTY (() to adjust the slope of ramp waveform.
4. Adjust AMPL (12) knob to control output amplitude of ramp waveform.
5. Pull out AMPL (12) knob to obtain 20dB attenuation of output.

 

TTL/CMOS signal output

1. First select Range (7), rotate FREQ (13) to set required frequency range.
2. Connect BNC connector of TTL/CMOS (20) to oscilloscope or to other experiment circuit for observing output signal.
3. At this moment, output is square waveform fixing to TTL level; suits for general TTL integrated circuit.
4. If square waveform of CMOS level is required, can pull out CMOS (10) knob to adjust voltage level.

 

Variation of external voltage-controlled frequency

This mode of operation allows the user to adjust the frequency of the function generator with an external DC control Voltage. It also provides an easy way for your adjustment.

1. Select Function (8) first, then select Range (7), rotate FREQ (13) to set required frequency range.
2. Connect external control voltage (0 ± 10V) to the VCF (21) connector via a suitable lead, and generate signal from Output (22)
3. Other adjustment, such as AMPL (12) switch can change amplitude of signal, or get attenuation; adjust Offset (11) for DC level, rotate Duty (9) switch can change output signal of pulse or ramp waveform etc.