Power meters and power analysers are not only becoming multi-functional, but are also being incorporated in other testing instruments
By Richa Chakravarty
Wednesday, April 16, 2014: In testing instruments, it is necessary to accurately measure and monitor power and voltage, which is done with the help of power analysers and power meters. Both can measure power and check energy consumption.
Today, power analysers perform multiple functions—they precisely measure direct current, alternating current, AC voltage, DC voltage, the intensity of DC or AC, phase rotation and idle, and apparent and effective power. They are also used for R&D work on inverters, motor drives, lighting systems and electronic ballasts, UPS systems, aircraft power systems, transformer testing and other power conversion devices.
On the other hand, power meters can accurately measure the power of RF and microwave signals, and their applications include testing the output power of communication base-station transmitters, cellular telephones, radar system equipment, and much more.
As technology and measuring techniques advance, a lot of changes are happening in the power analyser and power meter domains.
The latest in power meters
The power meters currently available in the market provide the best accuracy by determining sensitivity, maximum output power or the linearity of an RF component. Generally, high-end power meters require an external power sensor that can measure with an accuracy of 0.1 dB or better. Power meters can operate down to -70 dBm. They are also suitable for sensors that range from high power models and high frequency models to high bandwidth models for peak power measurement. Power meters are either single-channel or dual-channel instruments, with each channel requiring its own sensor.
Response to quick RF signals: Today, power meters can respond to the quick pulsed RF signals. To examine parameters like peak power, average power, rise time, fall time, overshoot and undershoot, power sensors must be fast, provide a wide bandwidth and offer a high dynamic range. But the sensors must be matched with an appropriate power meter to produce valuable data. Power meters not only process the continuous flow of measurement data, but they need to compile the data and display the signal waveform on their screens in a way that fully matches the actual RF signal.
Anritsu’s MA24105A inline peak power sensor is a compact and economical alternative to bench-top instruments. “With high accuracy, it eliminates errors otherwise introduced by attenuators. It has the widest dynamic range among inline power sensors, which enables high crest factor measurements and eliminates the need for lower power sensors. Also, its power graph feature facilitates and makes real time circuit tuning/monitoring on the bench much easier,” says Madhukar Tripathi, regional manager, Anritsu India Pvt Ltd.
Compact design: Yokogawa’s WT300 series of digital power meters is popular for its compact design. These are 5th generation power meters offering a wide current input range. It is a high performance low cost series of products that offers updated and innovative measurement functions, which benefit the engineers working with basic electrical power measurements. This series is an ideal measurement solution for doing stand-by power measurements.
Sampling performed at random intervals: Some power meters, like Boonton’s 4540 series RF peak power meters, not only utilise fast sampling on the measured signal, but offer an additional feature in which sampling is performed at random intervals. These meters have one channel that offers versatile power measuring systems with the capability of making over 20 different power related measurements on captured signals. Features like a high dynamic range, a rise time of less than 7ns and an effective time resolution of 200 ps provide the greatest detail in signal waveform analysis. These meters are the instruments of choice for capturing, displaying and analysing RF power in both the time and statistical domains.
The latest in power analysers
Today, power analysers have many features such as insulated current input, measurement of harmonics, etc.
Power analysers provide complete test solutions when being used for compliance testing or for overall power-conversion performance and efficiency. Tektronix’s PA1000 offers good overall performance in its class, with 0.05 per cent basic accuracy and a 1 MHz measurement bandwidth. “The PA1000 offers industry leading value with standard features including LAN, USB and GPIB interfaces, harmonic analysis, and PC software that cost extra on many analysers. This is the best choice for making precision power measurements on single-phase power supplies and all types of products connected to the AC line,” informs Sai Venkat, India marcomm, Tektronix India.
Incorporating power analysers with other instruments: Most players offer many products with multiple functions in one unit. Teledyne LeCroy has launched high definition oscilloscopes (HDO) with a power analysis package. This is a 12-bit HDO with a large memory and high sampling rate. Since the ADC is 12-bit, it provides a resolution that is 16 times better than the conventional 8-bit oscilloscopes. “The power analyser is based on our popular HD4096. Apart from power analysis, the HDO also provides several options on the same instrument like spectrum analysis, serial data trigger and decode, etc,” says Prabhanjana Rao, regional sales manager, India, SE Asia and ANZ, LeCroy India.
Agilent also offers a highly integrated instrument that combines four DC power supplies, a digital multimeter, oscilloscope, arbitary wave form generator and datalogger.
Making a purchase decision
Users should always evaluate their requirements before purchasing a power meter or an analyser, as the applications of both differ. Emphasis should be placed on the accuracy class of the device. The higher the accuracy class, the better the performance. The device should match the requirements—for example, whether the power analysis is for single-phase or three-phase. It should be able to measure the maximum values of voltage and current, and should also be able to analyse all kinds of harmonics.
Due to the large variance in product offerings and specifications, a detailed comparison is the best way to evaluate power sensors before making a purchase decision. Besides, basic factors like frequency range, dynamic range, accuracy, calibration, speed of measurements and triggering continue to be critical to the selection process. So these factors must be evaluated.
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Anritsu’s MA24105A power meter |
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• • Enables high crest factor measurements and eliminates the need for lower power sensors • True-RMS detection enables accurate CW and modulated power measurements • Forward and reverse measurements; measures both transmitted power and reflections from antenna using single in-line tool • High power handling capacity and low current consumption (100 mA) |
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Agilent’s N8262A P-series of power meters |
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• 30 MHz video bandwidth, with fast continuous sampling at 100 Msamples/s • Zero and calibrate while connected to the DUT • 50 MHz to 40 GHz frequency range; USB, LAN and GPIB connectivity • Flexible display formats, 15-point pulse parameter characterisation; limit and alert functions for remote monitoring |
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Yokogawa’s WT300 series of digital power meters |
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• DC measurement: 0.5 Hz to 100 kHz frequency range • Measures all AC and DC parameters • Compact design (half-rack size) • Standard USB, and GPIB or RS232 interfaces |
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Teledyne LeCroy’s HD4096 HDO power analyser |
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• Automatic detection and measurement of turn on and off conduction losses • Colour coded waveform overlay for easy identification of power loss and streamlined user interface • Automatically updated measurements and displays with proper power terminology • Dedicated interface for probe set up and configuration |
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Tektronix’ PA1000 power analyser |
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• • High measurement accuracy of 0.05 per cent, 1 MHz bandwidth /1 ms/s sample rate for demanding test requirements • Up to 600 VRMS voltage input • Up to 20 ARMS current input • Dual internal current shunts maximise accuracy for high and low current measurements • Easy data export to USB flash drive or remote PC software, for reporting and analysis |
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Agilent’s N6705B DC power analyser |
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• • Measure and display voltage, current versus time to visualise power into the DUT • Control DC bias supply ramp-up/down rates • Generate DC bias supply transients and disturbances • Log data for seconds, minutes, hours, or even days to see current consumption or capture anomalies |
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