The low frequency signal generator is an instrument for providing electronic signals with electrical requirements that meet certain technical requirements. The following uses the FJ-XD22PS low-frequency signal generator as an example to introduce the use of the low-frequency signal generator. This kind of instrument is a multi-purpose measuring instrument. It can output five kinds of waveforms such as sine wave, rectangular wave tip pulse, TTL level and single pulse. It can also be used as a frequency meter to measure the frequency of the external input signal.
Figure A-2 FJ-XD22PS low frequency signal generator
2.1 FJ-XD22PS low frequency signal generator panel introduction
FJ-XD22PS low frequency signal generator panel is shown in Figure A-2: 1. Power switch; 2. Signal output terminal; 3. Output signal waveform selection button; 4. Sine wave amplitude adjustment knob; 5. Rectangular wave, sharp pulse Wave amplitude adjustment knob; 6. Rectangular pulse width adjustment knob; 7. Output signal attenuation selection button; 8. Output signal band selection button; 9. Output signal frequency coarse adjustment knob; 10. Output signal frequency fine adjustment knob; Secondary pulse button; 12. Signal input terminal; 13. Six-digit digital display window; 14. Frequency meter internal measurement, external measurement function selection button (press: external measurement, bounce: internal measurement); 15. Measurement frequency button; 16. Measurement cycle button; 17. Count button; 18. Reset button; 19. Frequency or period unit indicates LED; 20. Measurement function indicator LED.
2.2 Main technical performance
1. Signal source part (1) Frequency range: 1Hz - 1MHz, which can be continuously adjusted in six steps by frequency band selection and fine adjustment of frequency coarse adjustment;
(2) Frequency drift: 1 file ≤ 0.4%; 2, 3, 4, 5 files ≤ 0.1%; 6 files ≤ 0.2%;
(3) Sine wave: frequency characteristic ≤ 1dB (6th gear ≤ 1.5db), output amplitude ≥ 5V, nonlinear distortion of waveform: 20HZ-20KHZ ≤ 0.1%;
(4) Positive and negative rectangular pulse wave: the duty cycle adjustment range is 30%-70%, before and after the pulse is ≤40ns; waveform distortion: at the rated output amplitude, the front and rear overshoot and the top tilt are less than 5%;
Output amplitude: high resistance output ≥10VPP, 50Ω output ≥5VPP;
(5) Positive and negative spikes: pulse width 0.1μs, output amplitude ≥5VPP.
2. Frequency meter section (internal and external):
(1) Function: frequency, period, count six-digit digital tube (eight-segment red) display;
(2) Input waveform type: sine wave, symmetrical pulse wave, positive pulse;
(3) Input amplitude: 1V ≤ pulse positive peak ≤ 5V, 1.2V ≤ sine wave ≤ 5V;
(4) Input impedance: ≥ 1MΩ;
(5) Measurement range: 1HZ-20MHZ (accuracy: 5×10-4±1 words);
(6) Counting: Counting rate: waveform period ≥ 1uS, counting range: 1-98340.
2.3 Basic operations
1. Connect the power cable to the 220V, 50HZ AC power supply. It should be noted that the grounding pin of the three-core power socket should be properly connected to the ground to avoid interference.
2. Rotate each output on the panel to the minimum before starting the machine.
3. In order to obtain sufficient frequency stability, preheating is required.
4. Frequency adjustment: The frequency band button on the panel is used for band selection. Press the corresponding button, then adjust the coarse and fine adjustment to the desired frequency. At this time, the “inside and outside measurement†button sets the internal measurement position, and the frequency of the output signal is displayed by a six-digit digital tube.
5. Waveform conversion: Press the corresponding waveform key according to the type of waveform required. The waveform selection keys are from left to right: sine wave, rectangular wave, sharp pulse, TTL level.
6. The output attenuation has five steps of 0dB, 20dB, 40dB, 60dB, and 80dB. If necessary, press the “0dB†button if no attenuation is needed. Otherwise, there is no output.
7. Amplitude adjustment: The sine wave and pulse wave amplitude are adjusted by the sine wave amplitude knob and the pulse wave amplitude knob, respectively. This machine fully considers the inadvertent short circuit of the output and adds certain safety measures, but do not make artificial short circuit experiments.
8. Rectangular wave pulse width adjustment: Adjusted by the rectangular pulse width adjustment knob.
9. “Single†trigger: When using a single pulse, first raise all six frequency keys, pulse width potentiometer clockwise to the end, tap “single†to output a positive pulse; pulse width potentiometer counterclockwise Rotate to the end, tap “Single†to output a negative pulse, the single pulse width is equal to the time the button is pressed.
10. Use of frequency meter: The frequency meter can perform internal and external measurement. The “internal and external measurement†function key is externally tested when pressed, and it is internal measurement when it is raised. The frequency meter can realize frequency, period and count measurement. The function switch can be realized by tapping the corresponding button switch, please also pay attention to the function indication of the corresponding LED on the panel. When the frequency is measured, the "Hz or MHz" LED is lit, and the "ms or s" LED is illuminated during the measurement period. In order to ensure the measurement accuracy, the period measurement is used when the frequency is low, and the frequency measurement is used when the frequency is high. If you find that the overflow shows "-- -- -- -- -- --", press the reset button to reset. If you find that the three function indicators are on at the same time, you can turn it off and then turn it back on.
2.4 Measurement examples
Example: The FJ-XD22PS low-frequency signal generator outputs a sine wave with a frequency of 1000 Hz and an effective value of 10 mV.
Follow these steps:
1. After powering on for a few minutes, press the “~†key in the waveform selection button, and the output signal is a sine wave signal.
2. Let the “inside and outside†frequency measurement keys be in the pop-up state, and the frequency meter internally measures the output signal frequency.
3. Press the output attenuation "20dB" button, the sinusoidal signal is attenuated by 20dB and output.
4. Press the frequency band to select the “1K—10K†button, and the output signal frequency is continuously adjustable from 1KHz to 10KHz.
5. Tap the “Frequency†button in the measurement function selection. The red LED above the button is lit. The number displayed in the window is the frequency of the output signal. The “Hz†red LED on the upper right side of the window is bright, indicating the frequency unit. Is Hz.
6. Adjust the frequency “coarse adjustment†knob until the displayed frequency value is close to 1000Hz, then change the frequency “fine adjustment†knob until the displayed frequency value is 1000 Hz.
It must be noted that the display of the frequency measuring circuit of the signal generator lags behind the adjustment, so the rotation of the knob is required to be slower; the signal generator itself cannot display the voltage value of the output signal, so an AC meter is required to measure the output voltage. When the output voltage does not meet the requirements, select a different attenuation and then adjust the amplitude knob of the output sinusoidal signal until the output voltage is 10mV.
To observe the output signal waveform, you can enter the signal into the oscilloscope. Need to output other signals, you can refer to the above steps, no longer one by one.
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