Signal Generators are used in various industries to create signals that simulate behavior of system. Frequency Counters are instruments for measuring frequency
Generators / Counters
Signal Generators are used in various industries to create signals that simulate behavior of system. With known signals output from the generator, troubleshooting and design of other devices is simplified. Frequency Counters are instruments for measuring frequency and are available a as a stand-alone device or built-in capability of a function generator.
AM/FM Signal Generators
AM/FM Signal Generators go beyond an RF Signal Generator to modulate the signal. Make sure the instrument specifications clearly state AM/FM modulation is included or available optionally. The FM RF broadcasting band for example, typically in the range of 87.5 – 108 MHz worldwide, is confusing because it is not the same as the Frequency Modulation (FM) method of modulation and similarly for Amplitude Modulation (AM).
If an RF Signal Generator only instrument is needed, TEquipment offers them.
Visit Signal Generators / Counters > RF Signal Generators
An Audio Generator is a signal generator designed for audio applications with low frequency (< 1MHz) signal generation, specifically for audio bandwidth. Audio generators feature very low distortion sine wave. Models will have a square wave output in addition to sine wave.
A Frequency Counter is standalone instrument or capability of an instrument for measuring frequency. Frequency is a measure of how fast a repetitive signal repeats per unit time and commonly measured in Hz (cycles per second). Frequency counters typically measure the number of pulses or oscillations per second in a waveform.
Selection considerations for Frequency Counters
- Frequency Range
- Measurement functions such as frequency, period ratio, time interval, pulse width, rise/fall time, phase angle, duty cycle, RPM, totalization of pulses
Function and arbitrary waveform generators are among the most important and versatile pieces of electronic test equipment. In electronic design and troubleshooting, the circuit under scrutiny often requires a controllable signal to simulate its normal operation. The testing of physical systems and transducers often needs stable and reliable signals. The signal levels needed range from microvolts to tens of volts or more.
Modern DDS (direct digital synthesis) function generators are able to provide a wide variety of signals. Today's basic units are capable of sine, square, and triangle outputs from less than 1 Hz to at least 1 MHz, with variable amplitude and adjustable DC offset. Many generators include extra features:
- Higher frequency capability
- Variable symmetry
- Frequency sweep
- AM /FM modulation
- Gated burst mode
- More advanced models offer a variety of additional waveforms
- Arbitrary Waveform Generators can supply user-defined periodic waveforms
Function generators are used where stable and repeatable stimulus signals are needed.
Here are some common uses and users:
- Research and development
- Educational institutions
- Electronic and electrical equipment repair businesses
- Stimulus/response testing, frequency response characterization, and in-circuit signal injection
- Electronic hobbyists
There are a variety of function generators on the market spanning the cost range from a few tens of dollars to tens of thousands of dollars.
Arbitrary Function Generators (AFG) vs. Arbitrary Waveform Generators (AWG)
Arbitrary generators can be classified into arbitrary/function generators (AFG) and arbitrary waveform generators (AWG). The arbitrary/function generator (AFG) serves a wide range of stimulus needs; in fact, it is the prevailing signal generator architecture in the industry today. Typically, this instrument offers fewer waveform variations than its AWG equivalent, but with excellent stability and fast response to frequency changes. If the DUT requires the classic sine and square waveforms (to name a few) and the ability to switch almost instantly between two frequencies, the arbitrary/function generator (AFG) is the right tool. An additional virtue is the AFG’s low cost, which makes it very attractive for applications that do not require an AWG’s versatility.
The AFG shares many features with the AWG, although the AFG is by design a more specialized instrument. The AFG offers unique strengths: it produces stable waveforms in standard shapes, particularly the all-important sine and square waves – that are both accurate and agile. Agility is the ability to change quickly and cleanly from one frequency to another.
Most AFGs offer some subset of the following familiar wave shapes:
While AWGs can certainly provide these same waveforms, today’s AFGs are designed to provide improved phase, frequency, and amplitude control of the output signal. Moreover, many AFGs offer a way to modulate the signal from internal or external sources, which is essential for some types of standards compliance testing.
In the past, AFGs created their output signals using analog oscillators and signal conditioning. More recent AFGs rely on Direct Digital Synthesis (DDS) techniques to determine the rate at which samples are clocked out of their memory.
The arbitrary waveform generator (AWG) can produce any waveform you can imagine. You can use a variety of methods – from mathematical formulae to “drawing” the waveform – to create the needed output. Fundamentally, an arbitrary waveform generator (AWG) is a sophisticated playback system that delivers waveforms based on stored digital data that describes the constantly changing voltage levels of an AC signal. It is a tool whose block diagram is deceptively simple. To put the AWG concept in familiar terms, it is much like a CD player that reads out stored data (in the AWG, its own waveform memory; in the CD player, the disc itself) in real time. Both put out an analog signal, or waveform.
Parameters typical to Arbitrary Waveform Generators (AWGs)
- Memory Depth (record length). Determines the maximum number of samples that can be stored. Higher memory depth permits reproducing more complex waveforms
- Sample Rate. Usually specified in terms of megasamples or gigasamples per second, denotes the maximum clock or sample rate at which the instrument can operate
- Bandwidth. An instrument’s bandwidth is an analog term that exists independently of its sample rate. The analog bandwidth of a signal generator’s output circuitry must be sufficient to handle the maximum frequency that its sample rate will support. In other words, there must be enough bandwidth to pass the highest frequencies and transition times that can be clocked out of the memory, without degrading the signal characteristics
- Vertical (Amplitude) Resolution. Vertical resolution pertains to the binary word size, in bits, of the instrument’s DAC, with more bits equating to higher resolution. The vertical resolution of the DAC defines the amplitude accuracy and distortion of the re-produced waveform
- Horizontal (Timing) Resolution. Horizontal resolution expresses the smallest time increment that can be used to create waveforms
- Region Shift. The region shift function shifts a specified edge of a waveform either right or left, toward or away from the programmed center value. If the specified amount of the shift is less than the sampling interval, the original waveform is re-sampled using data interpolation to derive the shifted values. Region shift makes it possible to create simulated jitter conditions and other tiny edge placement changes that exceed the resolution of the instrument
- Output Channels. Many applications require more than one output channel from the signal generator
- Digital Outputs. Some AWGs include separate digital outputs
- Filtering. Filtering allows you to remove selected bands of frequency content from the signal
- Sequencing. Permits repeating sections of the waveform saving valuable memory
- Tools to create and edit waveforms as well as import data created outside the tools
In real life applications, noise is inherent in nature and exists in electronic devices. For this reason, it is often important to have a noise signal inject into a device under test (DUT) to test its behavior in a more realistic simulated scenario. There are various types of noises, and two of the most common types are white noise and pink noise. With the capabilities of an AWG, these noise can be approximately simulated at the output of the generator. White noise has a flat power spectrum and equal power per unit frequency, while pink noise has equal power per octave.
If you choose to test an audio system using noise, use pink noise, as you might put too much energy into the tweeters if you use white noise. Pink noise in an audio system is useful because if you listen carefully and hear sounds that don't sound like noise, you may have found an imperfection in the audio system's response.
Programmable Pulse Generators, also called Pulse Pattern Generators, output square waves for use in research and testing of digital systems and circuits.
Some DDS Function Generators supply pulses as a standard feature. These generators often let you control the pulse width, pulse repetition rate, and rise and fall times. Arbitrary Waveform Generators (Arbs) can have pulses programmed with the desired pulse shape. While this is more work than the other methods presented here, it gives you flexibility to get (nearly) exactly the pulse shape you want. For Function Generators and Arbitrary Waveform Generators visit Generators /Counters > Function generators on the TEquipment website.
Dedicated Pulse Generators offer simplicity of use versus function generator or arb with more menus. BK has two very high performance pulse generator models to consider.
If you need lower duty cycle pulses, the following approach might work. You can set the pulse width by setting up a square wave with a frequency of 1/(2τ), where τ is the pulse width in seconds, and the appropriate DC offset to make it a pulse with the desired polarity. Then change to external triggering and trigger the generator with another generator at the desired pulse repetition rate. A handy, low-cost secondary generator for triggering the pulses is the B&K 3003 hand-held generator, which can generate sine and square waves from 0.1 Hz to 10 MHz. You may need to operate the function generator in burst mode for this to work.
RF Signal Generator
Radio Frequency (RF) Generators create continuous waves (CW) that can be used for research and troubleshooting of RF equipment and components. Example applications for RF Signal Generators are
- Bluetooth (2.4 GHz)
- GPS (1.2-1.6 GHz)
- WiFi (2.4 GHz)
RF Signal Generators have maximum frequencies that vary per model, but generally accepted maximum is 6 GHz, which overlaps with Microwave Generators that start in the MHz range up to 20 GHz maximum. Frequency is a measure of how fast a repetitive signal repeats per unit time and commonly measured in Hz (cycles per second).
RF Signal Generator Selection Advice
- Know the Frequencies for the application(s)
- Is a multifunction device needed?
- Some models have Function Generator capability for other waveforms
- If AM/FM modulation is needed, then make sure it is clearly specified in the specifications for the signal generator as included or available optionally. The FM RF broadcasting band for example, typically in the range of 87.5 – 108 MHz worldwide, is confusing because it is not the same as the Frequency Modulation (FM)method of modulation and similarly for Amplitude Modulation (AM).
TEquipment offers AM/FM signal generators.
Visit Signal Generators / Counters > AM/FM Signal Generators
- If application is for a Noise Generator (Noise Source) , then
visit Signal Generators / Counters > Noise Generators
Typically RF Signal Generators are bench models but a low cost handheld application: Handheld RF Signal Generator outputs two stable CW carriers. Popular with CATV installers and service technicians who align and test the return path. It is also handy for measuring insertion loss of cable, splitters, taps, and more when used in conjunction with a signal level meter or spectrum analyzer.
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