Common faults and precautions for signal generators

A signal generator is a device that provides electrical signals of various frequencies, waveforms and output levels. It is used as a signal source or excitation source for testing when measuring the amplitude characteristics, frequency characteristics, transmission characteristics and other electrical parameters of various telecommunications systems or telecommunications equipment, as well as when measuring the characteristics and parameters of components. Signal generators, also known as signal sources or oscillators, are widely used in production practice and technology fields.

The use of signal generators has become very common, so various failures will inevitably occur during use. Based on years of experience, Xi'an Antai Testing has learned that the common faults of signal generators are as follows:

1. Power failure: unable to boot normally

2. Output terminal failure: abnormal impedance; no signal; abnormal signal amplitude

3. Display failure: colorful screen; black screen

4. Button failure: The button does not respond; the adjustment knob does not respond.

5. Interface failure: storage media is not recognized; cannot be connected to the control system

6. Other usage issues, etc.

So how to avoid the above malfunctions of the signal generator?

1. Electrostatic protection

Static electricity can generate an instantaneous voltage of tens of thousands of volts, which can cause fatal damage to electronic components. Attenuators and mixers in signal sources are extremely sensitive to it and are particularly susceptible to damage. Therefore, when using signals, attention should be paid to electrostatic protection. It is worth mentioning that some static electricity cannot be detected by the human body, but it is enough to cause damage to the instrument.

1. Please use the standard 3-core AC power cord that comes with the signal source;

2. Static electricity will cause damage to the instrument and injury to the user. Proper grounding can avoid the accumulation of static electricity;

3. In the absence of protective grounding, please do not damage the grounding of wires, power cords or transformers;

4. Check the quality and polarity of the AC power supply. Generally, the voltage used by the meter is 100V, 120V, 220V, with an error of +/-10%, or 240V, with an error of +5%/-10%. Ground resistance should be less than 1 ohm. The voltage difference between neutral and ground is less than 1 volt. Install an uninterruptible power supply if necessary.

5. Instrument operators should wear electrostatic clothing, anti-static shoes, and anti-static bracelets. And test whether the anti-static preparation of the instrument is good before each use.

2. The output power of the signal generator cannot be too large

1. Avoid front-end damage caused by signal source output level settings. Reflection of the output signal or external bias may cause front-end overload and damage front-end devices. The typical reverse power protection level is 33dBm (2watt);

2. Reduce the signal amplitude to a smaller safe level before turning on the connected instrument or turning on and off the device under test to avoid accidental impact of the signal on the input and output ports of the signal source;

3. Avoid testing that allows DC or RF signals to be input to the RF output – to avoid front-end damage caused by signal source output level settings. Reflection of the output signal or external bias may cause front-end overload and damage front-end devices. The typical reverse power protection level is 33dBm (2watt);

4. Reduce the signal amplitude to a smaller safe level before turning on the connected instrument or turning on and off the device under test to avoid accidental impact of the signal on the input and output ports of the signal source;

5. Avoid testing systems that allow DC or RF signals to be input to the RF output port and IQ output port; when necessary, use DC blockers, limiters and external attenuators appropriately.

Frequent overloading of the output signal has a negative impact on the signal source and will reduce the service life of the signal source. Agilent's signal sources have different output powers with different models and options. Therefore, you should be familiar with the DataSheet of this model of signal source when using the signal source. Use the instrument within the power output range given in the DataSheet.

Keysight 33622A Waveform Generator

3. When testing active devices such as amplifiers. The output end of the signal source must be protected by reverse power. Do not press the output button when the RF cable is not tightened.

1. Pay attention to impedance matching. If the impedance matching is not good, the resulting reflected signal will directly enter the reverse protection circuit inside the signal source, causing an impact on the reverse protection circuit. The more frequent the impact, the more accelerated the aging of the directional protection circuit. Correctly setting the output power value and good impedance matching can delay the aging of the device and reduce the failure rate.

2. When testing a high-power repeater, there will be high reverse power, and a power attenuator must be added to the output end of the signal source.

4. If the device under initial test will produce DC bias, a DC blocker must be added to the output end of the test signal source.

After DC bias enters the output end of the signal source, it will affect the reverse power protection circuit of the signal source. Reduce service life.

5. Mechanical stress

Do not place heavy objects (such as high-power attenuators, etc.) on the output end of the signal source. 6. Maintain a good usage environment

Good grounding, ventilation and heat dissipation are necessary to extend the service life of the signal source.

1. The electrical environment in which Agilent instruments are used must meet Agilent’s requirements for power supply quality. Similar to the National Inspection Computer Room Class A standard.

2. Clean the air outlet of the signal source regularly to ensure that no dust blocks the heat dissipation of the instrument. Insufficient ventilation will cause overheating and damage to the instrument. The recommended operating temperature is 20-30°C, ensuring the ambient temperature is <35°C;

3. Please turn off the RF output when the signal source is not in use.

4. When the instrument is installed in the cabinet, ensure normal convection inside and outside the instrument. The ambient temperature must be below the product operating temperature, which is 4°C per 100 watts consumed. If the chassis consumes more than 800 watts of power, forced convection cooling must be used.

6. Handle instruments correctly

1. Use the handle to lift the instrument when transporting;

2. Avoid putting your hands on the front panel to lift the instrument. If it slips off, it will cause damage to the keyboard, knobs and connectors;

3. Please use a cart or two people to carry heavier instruments.

4. Use appropriate packaging when transporting.

Using non-professional packaging materials may cause damage to the instrument. Do not use styrene pellets as packaging material. It does not adequately protect the instrument and may cause damage to the instrument by generating static electricity. If possible please retain the original packaging for reuse.