Industries Information

Spectrum analyzers and signal analyzers are passive receivers, which displays the signal in the form of easily identifiable data.  Spectrum analyzers and signal analyzers display raw, unprocessed signal information such as voltage, power, period, wave shape, sidebands, and frequency. They can provide the user with a clear and precise window into the frequency spectrum. Spectrum analyzers and signal analyzers are used to analyze the electrical signals that are passing through or being transmitted by the system or device.  They are widely used in situations where design, manufacturing and field service or repair of electrical systems or devices is needed. By analyzing the characteristics of the signal once its gone through the device / system, the user can determine the performance, find problems, troubleshoot, etc. Depending upon the application, a signal could have several different characteristics. For example, in communications, in order to send information such as voice or data, it must be modulated onto a higher frequency carrier. A modulated signal will have specific characteristics depending on the type of modulation used. When testing nonlinear devices such as amplifiers or mixers, it is important to understand how these create distortion products and what these distortion products look like. Understanding the characteristics of noise and how a noise signal looks compared to other types of signals can also help in analyzing the device/system.

Important physical specifications to consider when searching for spectrum analyzers and signal analyzers include mounting and form factor.  Choices include handheld, portable or benchtop, and fixed.  The analyzer is usually an instrument based unit or pc-based unit.  Test types performed by analyzers include modulation, distortion, and noise.  Measuring the quality of the modulation is important for making sure a system is working properly and that the information is being transmitted correctly. In communications, measuring distortion is critical for both the receiver and transmitter.  Excessive harmonic distortion at the output of a transmitter can interfere with other communication bands. Because any active circuit or device will generate noise it is an important parameter to measure.  Tests such as noise figure and signal-to-noise ratio (SNR) are important for characterizing the performance of a device and/or its contribution to overall system noise.  Analysis types include fast Fourier transform (FFT) and swept-tuned.  The Fourier analyzer basically takes a time-domain signal, digitizes it using digital sampling, and then performs the mathematics required to convert it to the frequency domain, and display the resulting spectrum.  It is as if the spectrum analyzers and signal analyzers are looking at the entire frequency range at the same time using parallel filters measuring simultaneously. The most common type of spectrum analyzer is the swept-tuned receiver.   It is the most widely accepted, general-purpose tool for frequency-domain measurements.

Important frequency performance specifications to consider when searching for spectrum analyzers and signal analyzer include the frequency range, frequency accuracy, and frequency resolution.  It is important that a spectrum analyzer will cover the fundamental frequencies of the application, as well as harmonics or spurious signals on the high end, or baseband and IF on the low end. Frequency accuracy is often listed under the Frequency Readout Accuracy specification and is usually specified as the sum of several sources of errors, including frequency-reference inaccuracy, span error, and RBW center-frequency error. Resolution is an important specification when trying to measure signals that are close together and need to be distinguishable from each other.  The IF filter bandwidth is also known as the resolution bandwidth (RBW).  Input and output specifications to consider include number of input channels, dynamic range, and number of output channels.

Specialty lab and test equipment includes specialty or proprietary products and accessories related to laboratory testing. This lab equipment may include specialized instruments that are used to measure electrical quantities such as voltage, current, resistance, frequency and signal power as well as specialized test equipment for measuring signal power. Specialized electronic testing equipment may require highly specialized data acquisition systems for digitizing and processing multiple sensor or signal inputs designed to monitor, analyze and/or control systems and processes. Signal conditioning includes the amplification, filtering, converting, and other processes required to make sensor output suitable for rereading by computerized testing equipment.

Chart recorders and strip charts are data acquisition tools that are often used with specialty lab and test equipment and are used to generate a plot, graph or other visualization of data versus time. Not infrequently data loggers and data recorders are used with specialty lab and test equipment to acquire digital data from sensors and other signals. Specialized lab equipment takes advantage of them to store data for subsequent downloads to a host PC, but may also be used to provide real-time features such as monitors and alarms. Sometimes environmental test chambers are used in concert with specialty lab and test equipment to ensure the reliability of industrial products, especially electronic items, through prolonged exposure to one or more environmental parameters. Logic analyzers are used with specialty lab equipment to characterize and debug hardware, design and test firmware and software, and perform synthesis integration. An important complement to specialty lab and test equipment, spectrum analyzers and signal analyzers display raw, unprocessed signal information such as voltage, power, period, wave shape, sidebands, and frequency. They can provide the user of specialized lab equipment with a clear and precise window into the frequency spectrum.

Signal generators and waveform generators are used to test and align all types of transmitters and receivers, to measure frequency and to generate a signal, waveform or noise source. Signal generators can use AC energy, audio frequency (AF) and radio frequency (RF) to function.

They are also used to troubleshoot various electronic devices and to measure frequency. The function of a signal generator is to produce alternating current (AC) of the desired frequencies and amplitudes with the necessary modulation for testing or measuring circuits. It is important that the amplitude of the signal generated by the signal generator be correct. In many signal generators, output meters are included in the equipment to adjust and maintain the output at standard levels over wide ranges of frequencies. When using the signal generator, the output test signal is connected to the circuit being tested. The progress of the test signal can then be tracked through the equipment by using electronic voltmeters or oscilloscopes. In many signal generators, calibrated networks of resistors, called attenuators, are provided. Attenuators are used in signal generators to regulate the voltage of the output signal. Only accurately calibrated attenuators can be used because the signal strength of the generators must be regulated to avoid overloading the circuit receiving the signal.

Signal generators and waveform generators typically come as a portable or benchtop instrument, a fixed instrument, or a PC-based instrument or module.  Common generator types include continuous wave, function, pulse, signal and sweep. A source that can produce a sine wave is referred to as a CW source.  The frequency and amplitude of the sine wave can be set in most CW sources. Function generators create square waves by applying a bipolar sine wave to a comparator’s input. A pulse is a short burst of signal(s) generated by instrument. Signal generators output signals, or sine waves that carry information.  There are numerous methods for adding information to sine waves.  Basic signal generators have frequency, amplitude and phase modulation capabilities.  More advanced signal generators have pulse and IQ modulation capabilities. A swept source adds the ability to automatically vary the output frequency or amplitude of a sine wave over a range of frequencies or amplitudes in a controlled manner.

Frequency characteristics that are important to consider when searching for signal generators and waveform generators include maximum input channels, frequency range, frequency resolution, frequency accuracy, and switching speed. The maximum input channels refer to the maximum number of all analog input channels, general and specific types. The frequency range specifies the range of output frequencies the generator can produce. The frequency resolution is the smallest frequency increment the generator can produce.  The generator’s internal clock determines the frequency accuracy.  It is a measure of how accurately the source frequency can be set.  Operation features to consider include on board reference, on board oscillator, reverse power protection, and battery powered.  An on board reference is a source of information, usually referring to the clock, which supplies timing information. An oscillator creates the basic electrical fluctuation (AC) that is used to create the waveforms. Reverse power protection prevents signals traveling the wrong direction from damaging the source.

Additional specifications to consider when searching for signal generators and waveform generators include user interface, connections to the host, memory and storage, computer bus, display options, and environmental parameters.

Scalar network analyzers measure the amplitude portion of scattering or S-parameters, reflection and transmission coefficients between the incident and reflection waves that describe a device’s behavior under linear conditions at the microwave frequency range. Most scalar network analyzers are used to measure transmission gain, transmission loss, return loss, and standing wave ratio (SWR). Traditional devices use diode detectors to convert a radio frequency (RF) input signal to a proportional DC level. This method is less expensive than the tuned-receiver approach, but inherently scalar in nature. Some scalar network analyzers include a 5 ¼” floppy drive or a 3 ½” disc drive. Others include a compact disc (CD) drive for loading programs or storing data. Tape drivers and display options are also available. For example, analog meters display S-parameter values with a simple visual indicator such as a needle. Digital readouts use numeric or application-specific display. With video displays, data is presented via a cathode ray tube (CRT), liquid crystal display (LCD) or multi-line form.

There are several form factors or instrument styles for scalar network analyzers. Portable or benchtop devices can be moved with relative ease and used in a variety of applications. They may include a case or handle, but are not necessarily designed for hand held use. Fixed scalar network analyzers are kept in one location and meant to be used in one place. They are usually stand-alone devices. PC-based or "black box" instruments and modules do not include an integral display, but instead interface to a computer. They typically plug into the backplane or motherboard, or otherwise interface directly with the computer bus. For each form factor or instrument style, operating temperature and operating humidity are important considerations.

Performance specifications for scalar network analyzers include frequency range, frequency accuracy, frequency resolution, output power range, and nominal input impedance. Typically, applications such a wireless communications require higher frequency capabilities. For example, 900 MHz applications require devices with a high frequency of 10 * 900 MHz for a total of 9 GHz. Other applications must be able to measure lower frequency baseband or intermediate frequency (IF) signals. Frequency accuracy is specified as the sum of several sources of errors, including frequency-reference inaccuracy, span error, and resolution bandwidth (RBW) center-frequency error. Frequency resolution is an important specification for applications that measure close signals that need to be distinguished from one another. Output power is the 1-dB compression point that results in a 1 dB decrease in amplifier gain. Nominal input impedance is the amount of load that an input places on the signal source that drives the load. High input impedance is generally desirable and implies that little change in the signal is expected when the circuit is connected. The most common input impedances for scalar network analyzers are 50 Omega: Ohms and 75 Omega: Ohms.

There are several interfaces for scalar network analyzers. RS232, RS422, and RS485 are common serial interfaces. Universal serial bus (USB) is a 4-wire, 12-Mbps serial bus for low-to-medium speed connections. IEEE 1394 or FireWire® is an interface standard adopted by the Institute of Electrical and Electronics Engineers (IEEE) for very fast digital data transfers. FireWire is a registered trademark of Apple Computer, Inc. The general-purpose interface bus (GPIB) is designed to connect computers, peripherals and laboratory instruments. Small computer systems interface (SCSI) is an intelligent I/O parallel peripheral bus. Transistor-transistor logic (TTL) is a common type of digital circuit in which the output is derived from two transistors. Some scalar network analyzers use parallel channels or Ethernet networks. Others use modems or communicate via radio transmissions or telemetry.  

Oscilloscopes translate an electronic signal into a pattern or waveform on a screen. As it is traced across the screen, the waveform creates a signature of the signal’s characteristics. Specifications for oscilloscopes include bandwidth, number of input channels, number of trigger inputs, and resolution. Bandwidth is the frequency range over which oscilloscopes meet their accuracy specifications. Accuracy degrades at lower and lower frequencies unless the oscilloscope is capable of direct current (DC) response. Accuracy also degrades at higher frequencies near resonance and beyond, causing the output response to roll off. The number of input channels is the number of possible, simultaneous signal measurements. Channels can be differential or single-ended. The number of trigger inputs is the number of digital or discrete channels that oscilloscopes use for low-level on-off signals. Resolution refers to the degree of fineness of the digital word representing the analog value. A ten-bit number contains 210 (1024) increments and allows a 0 - 10 V signal to be resolved into approximately 0.01 V increments. A 12-bit representation provides  212 (4096) increments of 0.0024 V for the same signal.

Oscilloscopes use a host interface to communicate with a host computer or other electronic device. Oscilloscopes can use a serial port, parallel port, modem or telephone line, universal serial bus (USB), general-purpose interface bus (GPIB), small computer systems interface (SCSI), or Ethernet connection. Serial ports transfer data one bit a time. RS232, RS422, and RS485 are common serial interfaces. Parallel ports transfer more than one bit at time. Personal computer (PC) printer ports and Centronics ports use parallel communications. Modems (modulators/demodulators) are devices or programs that enable a computer to transmit data over telephone lines. Universal serial bus (USB) is a 4-wire, 12-Mbps serial bus for low-to-medium speed peripheral device connections to personal computers (PC). The general-purpose interface bus (GPIB) is designed to connect computers, peripherals and laboratory instruments so that data and control information can pass between them. Small computer systems interface (SCSI) is an intelligent I/O parallel peripheral bus with a standard, device-independent protocol that allows many peripheral devices to be connected to the SCSI port. Other specialized and proprietary host interfaces for oscilloscopes are also available.

Oscilloscopes provide many different features. Some devices have a relay or switch output for limit detection or other state signalling. Others are powered by a replaceable or rechargeable battery, or are designed to be used while held in one hand. Oscilloscopes that are rated for high-power applications can monitor and/or display currents and voltages associated with electrical power or high-power switching. Typically, these currents and voltages are much higher that standard sensor signal levels. In terms of storage capacity, oscilloscopes can include  a hard drive, nonvolatile memory, or on-board random access memory (RAM). Removable storage media devices such as tapes, diskettes, and PCMCIA cards are also available.

Oscilloscopes that are marketed in Europe Union (EU) countries should meet two important directives: Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronics Equipment (WEEE). RoHS requires manufacturers of electronic and electrical equipment to demonstrate that their products contain only minimal levels of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether. Waste Electrical and Electronics Equipment (WEEE) is and EU directive that is designed to encourage the reuse, recycling and recovery of electrical and electronic equipment. WEEE establishes requirements and criteria for the collection, treatment, recycling and recovery of such devices. WEEE also makes producers responsible for financing these activities, and requires retailers and distributors to provide a way for consumers to return used or obsolete equipment at no charge.

 Logic analyzers are devices used to monitor the performance of computers or to diagnose problems in other electronic systems. They use an oscilloscope to present complex digital data to a user, allowing the user to check particular operations of the electronic system. The proper selection of logic analyzers requires an understanding of application requirements and an analysis of performance specifications. Logic analyzer suppliers are located across North America and around the world. They conform to a variety of approvals and certifications. For example, in Europe, logic analyzers often bear the CE Mark.

Logic analyzers are used in development of computer systems and networks to find the source of hardware or software design flaws. Using a logic analyzer during the production phase can minimize the likelihood that serious problems with hardware or software will arise after a product goes to market. Logic analyzers are used to provide feedback on a variety of computer parameters or systems, including memory testing, testing input and output bandwidth, processor and bus support, networking, serial data validation and compliance, and signal integrity.

A PC based logic analyzer is a device used in conjunction with a personal computer to troubleshoot and verify performance parameters of digital circuits. A PC logic analyzer is usually a small profile device that connects to the PC through a parallel port or a universal serial bus (USB) port. PC logic analyzers use special connectors or probes to test different circuits. These signals are then interpreted by the logic analyzer device attached to the PC. The PC interprets this data using a logic analyzer software package that creates a virtual analyzer or oscilloscope on the computer monitor.

Logic analyzers are used to test circuits in embedded systems and microcontrollers, robotics, and automotive computers. Logic analyzers may also work in mixed signal systems that use both analog and digital signals.

LCR meters and impedance meters measures inductance (L), capacitance (C), and resistance or impedance (R). Instruments used for LCR measurements are built as universal and multifunctional devices. They enable automatic (triggered or cyclic) measurements of L, C, and R as well as other parameters such as quality and dissipation factors.  Instrument type, measurement specifications, test signal or source characteristics, and other measurements are important parameters to consider when searching for LCR meters and impedance meters.  Additional specifications that are important to consider include user interface options, display options, additional output options, general features and functionality and environmental parameters.

Instrument types include hand held, portable, and fixtured or permanent.  General measurements that are important to consider when searching for LCR meters and impedance meters include resistance or impedance range and accuracy, capacitance measurement range and accuracy, and inductance measurement range and accuracy.  Resistance or impedance is the opposition that a device or material offers to the flow of current, equal to the voltage drop across the element divided by the current through the element. Also known as electrical resistance. Also called impedance, parameters are Z or Rac.  A capacitor is a system of two conducting electrodes, having equal and opposite charges separated by a dielectric. The capacitance, C, of this system is equal to the ratio of the absolute value of the charge, q, to the absolute value of the voltage between bodies as: C=q/v. The unit of capacitance, the farad, is a large unit; practical capacitors have capacitances in microfarads, nanofarads and picofarads.  Self-inductance is defined as the relation between current, i, flowing through the coil and voltage, v, measured at its terminals. Also the property of an electric circuit or of two neighboring circuits whereby an electromotive force is generated in one circuit by a change of current in itself or in the other. One Henry (1 H) is the inductance of a circuit in which as electromotive force of one volt (1 V) is induced, when the current in the circuit changes uniformly by one ampere (1 A) per second (1 s).

Test signal or source characteristics that are important to consider when specifying LCR meters and impedance meters include basic accuracy, number of digits displayed, number of steps, test signal or frequency range, and response time.  Basic accuracy is the typical value at 1 kHz.  The number of digits displayed refers to the number of digits on the readout.  Number of steps in the measurement is important to consider.  The test signal frequency range is the frequency range at which the instrument operates.  Response time is the amount of time it takes for the LCR meters and impedance meters to make and display measurements.

Laboratory thermometers are used to measure temperatures or temperature changes with a high degree of precision. They are made of metal or glass and strengthened through processes such as thermal tempering or annealing. Several types of laboratory thermometers are commonly available. Liquid-in-glass thermometers are made of sealed glass and contain a fluid, usually mercury or red alcohol, whose volume changes relative to its temperature. Bimetallic strip thermometers include two different metals that are bonded together and expand at different rates as they warm up. Often, long bimetallic strips are wound into a coil and used with a dial. Electronic devices such as thermistors measure changes in electrical resistance and convert them to changes in temperature. Infrared thermometers are non-contact devices that convert infrared (IR) energy to an electrical signal that can be displayed in units of temperature. Other specialized or proprietary products are also available.

Laboratory thermometers measure temperatures in degrees Fahrenheit (F) or degrees Celsius (C). Graduated scalar divisions or test points determine the accuracy with which users can read each type of device. Typically, display numbers are etched or printed on the thermometer’s housing. With some devices, permanent pigmentation of graduations is used to improve readability. Features such as clip-on magnifiers help users read numbers on more detailed scales. Some laboratory thermometers can be fully immersed in the media being measured. Others can withstand only partial immersion. Devices encapsulated with polytetrafluoroethylene (PTFE) are suitable for monitoring acids or other hazardous materials. Teflon®, a registered trademark of DuPont, is a common, proprietary form of PTFE. Laboratory thermometers with a protective metal sheath and no-roll cap are commonly available.

Organizations such as the National Institute of Standards and Technology (NIST) and the American Society of Testing and Materials (ASTM) calibrate laboratory thermometers and provide traceability. NIST provides calibration services for a variety of laboratory thermometers that cover a temperature range from -196° C to 550° C (-321° F to 1022° F). Submitted devices must pass a preliminary examination for fineness and uniformity of graduation as well as freedom from moisture, gas bubbles, and cracks. The thermometers to be calibrated are placed in a constant temperature bath along with an NIST-calibrated standard platinum resistance thermometer (SPRT) that is traceable to the International Temperature Scale of 1990 (ITS–90). Special tests may also be conducted on industrial-grade platinum resistance thermometers, digital thermometers, and thermistors. ASTM-certified laboratory thermometers must also pass rigorous testing requirements.

Hardness testers measure a materials’ resistance to indentation.  Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth or projected area of the indentation. More simply put, when using a fixed force (load) and a given indenter, the smaller the indentation, the harder the material. Indentation hardness value is obtained by measuring the depth or the area of the indentation using one of many different test methods.  Hardness testers use one of several types of scales for determining the hardness of a sample.  These include Brinell, dynamic rebound, coating or nanoindentation, Rockwell, Vickers and Knoop and ultrasonic.  Methods include macro, micro and superficial testing.

Brinell hardness testers are widely used on castings and forgings.  This method applies a predetermined test force to a carbide ball of fixed diameter that is held for a predetermined time and then removed. The diameter of the indentation width is measured twice - usually at right angles to each other and averaged. A formula or chart is then used to convert the averaged measurements to a Brinell hardness number. Test forces usually range from 500 to 3000 kilograms (occasionally down to 1kg in less frequently used tests).

In dynamic rebound or impact hardness testers, a hammer or diamond tipped probe is dropped onto a sample and the rebound height or velocity change is measured and converted into a hardness reading.  The rebound height increases with increasing hardness.  These tests are less destructive than conventional static indentation tests and applied where even a small indent on a surface cannot be tolerated; e.g., forged rolls for printing.

Coating hardness testers use indentation, scratching or rubbing tests to evaluate the hardness or wear resistance of thin films of paint, sealants, adhesives, vapor deposits, CVD/PVD deposits or plated layers.

The Rockwell test method is defined in ASTM E-18 and is the most commonly used hardness tester operation method since it is generally easier to perform and more accurate than other types of hardness testing. Rockwell testers can be used on all metals except in conditions where the test metal structure or surface conditions would introduce too much variation, where the indentations would be too large for the application or where the sample size or shape prohibits its use. The Rockwell tester method measures the permanent depth of indentation produced by a force on an indenter.

Vickers and Knoop hardness testers can be used for Micro and Macro hardness testing. Typically loads are very light, ranging from a few grams to one or several kilograms, although "Macro" Vickers loads can range up to 30 kg or more.  The Microhardness testing operation according to ASTM E-384 specifies a range of loads between 1 to 1000 g.  There are two types of indenters; a square base pyramid shaped diamond for testing in a Vickers tester and a narrow rhombus shaped indenter for a Knoop tester. The Micro-hardness methods are used to test on metals, ceramics, and composites - almost any type of material.

In ultrasonic hardness testers, a probe tipped with an indenter is piezoelectrically resonated at an ultrasonic frequency. The probe is held against the sample with a spring and a small indentation is made. The frequency of the probe changes in proportion to the contact area of the indentation. The tester measures the frequency change, then calculates and displays the equivalent hardness value.

Frequency meters are instruments that provide analog outputs as frequencies that vary as a function of the applied input. They display values on a dial, usually with a needle or moving pointer. Frequency meters measure repetitions per unit of time, usually per second, of a complete electromagnetic waveform. Most devices are deflection meters that balance two opposing forces and indicate changes in balance. There are two basic types of defection meters: moving-coil meters and ratio meters. Moving-coil meters are electrically resonant circuits that consist of two coils tuned to different frequencies and connected at right angles to one another. Frequencies in the middle of the range equalize the currents in the two coils and allow the needle or pointer to indicate the midpoint of the scale. Changes in frequency create an imbalance between these currents, causing both the coils and the needle or pointer to move. Ratio meters use two frequency inputs: a known standard and an unknown amount. Frequency ratios are often expressed as Lissajous figures, a common means of comparative frequency measurement in electronics.

Important specifications for frequency meters include units of measure, frequency accuracy, and estimated weight. Some devices provide fuse protection on functions. Others provide robust center-pole meter movements. Battery powered devices can be operated without plug-in power and are suitable for a variety of field applications. Temperature compensated devices include programming or electrical components designed to counteract known errors caused by temperature changes. Frequency meters with mirrored scales improve readability by enabling users to avoid parallax errors. Devices with a range switch allow users to select the range of units to measure. Frequency meters with overload protection and diode testing are also available. Some devices are handheld and portable. Others are designed for benchtop or shop floor use.

Frequency meters are used in a variety of applications and industries. For example, some devices are used to monitor vibration levels from heavy equipment. Others are used to verify the frequency of RF signals independently of electronic circuitry which may be susceptible to interference from parasitic harmonics or cross modulation. Often, frequency meters that are used with RF signals provide a high degree of measurement accuracy and include calibration data.