Pat Hindle, MWJ Editor
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Pat Hindle is responsible for editorial content, article review and special industry reporting for Microwave Journal magazine and its web site in addition to social media and special digital projects. Prior to joining the Journal, Mr. Hindle held various technical and marketing positions throughout New England, including Marketing Communications Manager at M/A-COM (Tyco Electronics), Product/QA Manager at Alpha Industries (Skyworks), Program Manager at Raytheon and Project Manager/Quality Engineer at MIT. Mr. Hindle graduated from Northeastern University - Graduate School of Business Administration and holds a BS degree from Cornell University in Materials Science Engineering.

All about Function Generators

April 20, 2015

 This post is from Clark (Madison, Wisconsin) who has been working as a product & test engineer for the past 3 years:

Function generators are one of the stalwarts of electronics testing equipment. In fact, function generators are used throughout the life cycle of an electronic component – in its development, testing, and repair. Typically, a modern digital function generatorcreates electrical waveforms either in a continuous loop or a single-shot, across a variety of frequencies. It is these frequencies by which manufacturers differentiate the value of the function generator. Nowadays, the available variety of function generators online is very extensive, and usually categorized by frequency, which can range from the lower limit of 0 Hz to the top limit of 20 or even 50 MHz and beyond depending upon the make and model. One can check several websites like TRS RenTelco, Tektronix, Keysight, etc offering an extensive range of function generators which are quite dynamic, and can be minutely adjusted to replicate the currents that would typically pass through the device that is being tested.

Here are some examples of the many variables that can be fine-tuned on function generators:

  • The most important function of the function generator is waveforms, and usually waveform function generators (as they are also sometimes known) allow for a choice of waveforms from a variety of available options. Common waveforms produced by a function generator are sine, where the frequency signal curves from high to low voltage. In saw tooth, the wave gradually rises and suddenly drops. Triangular waveforms oscillate from high tolow voltage at fixed rates. Square waveforms are typified by a signal that goes straight from high voltage to low voltage. Lastly, a pulse waveform is quite similar to a square, with the only difference being the mark-space ratio which isn’t 1:1 as it is on the square waveform.
  • Most function generators can be adjusted to alter the amount of voltage it creates using the DC offset setting as well. As mentioned earlier, the frequency range over which the amount of voltage can be varied, and is pre-determined based on thechoice of the manufacturer of the function generator. Another setting commonly found on function generators is duty cycle. Duty cycle maintains the ratio of high and low voltage timings when you change from one waveform to the other.
  • The output level of function generators, though usually limited to 12 volts from one peak to another, can be changed continually. This option is available so that function generators can work on multiple circuits including TTL, or Transistor–transistor logic digital circuits which are commonly found on most common digital devices such as laptops, consumer electronics, computers and industrial controls among others.
  • Another important facet of function generators is the load it is capable of driving. Known as output impedance, on most function generators this will be set at 50Ω. Output figures will appear as half from the no-load number due to this 50Ω impedance level.
  • Digital function generators also come equipped with in-built stability control, achieved through the usage of a crystal-infused clock. Some function generators also have phase-lock capacities. Phase-lock allows the generator to be engaged with a clock signal externally, helping achieve a far greater degree of synchronization and accuracy in terms of the time of the output.
  • A function generator is well equipped to meet a variety of challenges when it comes to testing the functionality of electronic equipment. By taking apart a circuit board from the device and reproducing the frequencies generated within the device, the device’s behavior as a result of the passage of these frequencies can be observed.
  • The sheer variety of devices that can be tested using function generators is staggering. Everything from laser diodes and hydraulic valves, to medical equipment like ultrasound machines, pacemakers, defibrillators can be tested. A function generator can also be used on automotive ECUs or Engine Control Units, sensor signals in vehicles, and a variety of other vehicular electronics. Motherboards and other circuitry can also be checked for their vulnerability to power spikes. Audio devices such as amplifiers, microphones and electronic musical instruments can also be tested for feedback using a function generator, among its many other applications. 
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