February 3, 2014: Fast paced advances in technology pose a challenge to testing devices and equipment, hence manufacturers are now developing instruments that can meet the new requirements
By Richa Chakravarty
A clamp meter is a device used to measure the current in a wire. It helps in pinpointing issues in the system thus avoiding huge breakdown costs. Clamp meters can generally be categorised based on their measurement technology—typical sensing clamp meters and true RMS (TRMS) clamp meters. Both have their respective advantages and applications. The TRMS clamp meters, with their advanced circuitry and ability to accurately measure both sinusoidal as well as non-sinusoidal signals, are costlier than the average sensing clamp meters. Advances in technology are posing a challenge to testing devices and equipment, hence manufacturers of instruments are now developing models that can meet newer requirements. Users in India are now embracing power quality maintenance in a big way. Power maintenance is no longer restricted to energy auditors and has become an important aspect of daily maintenance. Taking a cue from this trend, companies in India have come out with new products such as power loggers, clamp meters with power capabilities and other application specific clamp meters for the domestic market.
The latest in the market
Today, major T&M players are focusing on some of the critical market requirements. These include harmonic distortion, inrush current, as well as power and energy measurements. Today’s clamp meters have built-in low pass filters, which help in keeping interference from other electronic components away and hence give users an accurate reading. Not only do these clamp meters offer overload protection that prevents damage to both meter and circuit, while protecting the user, they also offer the auto ranging feature that automatically selects the proper measurement range rather than the user having to perform manual ranging. A backlit display, easy to read characters, and a wide viewing angle make it easier for users to view the readings in all sorts of conditions. Apart from these, there are several other innovative features that T&M players are offering today.
Detachable displays: While wireless clamp meters have provided users the much-needed flexibility, Being able to remove the display adds further to the device’s versatility. Wireless technology allows the display to be carried up to 9.14m away from the point of measurement, without affecting measurement accuracy. Fluke’s 381 Series remote display TRMS AC/DC clamp meter offers a detachable, remote display for easier, faster and safer measurements. It offers up to 1000A AC and DC measurements, 1000V AC and DC voltage measurements and includes the iFlex flexible current probe that expands the measurement range to 2500A AC while providing increased display flexibility, the ability to measure awkward sized conductors and improved wire access. The 381 Series also has CAT IV 600V, CAT III 1000 V safety ratings, an integrated low pass filter and state of the art signal processing for noisy electrical environments.
Informs Manish Kwatra, managing director, Metro Electronic Products, “Clamps with multiple parameters like kWH, kVA, etc, with data logging facilities and a USB interface are the most preferred.”
A single instrument with multiple features: The Rish Clamp Power AC/DC clamp meter comes with a host of power and current measurement capabilities all packed into a single instrument. It comes in two variants—1000A AC/DC and 300A AC/DC current ratings both complying with CAT IV standards. The Rish Clamp Power combines the functions of a clamp meter, power quality meter and multimeter, which makes it an ideal tool in high current and power quality maintenance applications. It can measure power in 3-phase-3-wire or 3-phase-4-wire (symmetric as well as asymmetric) networks without the requirement for any manual calculations. Besides this, it comes with rotating clamp jaws which enables easy measurements in difficult positions – a patented feature. “Harmonic distortion is the normal consequence of a power system supplying electronic loads such as computers, variable frequency drives, electronic lighting ballasts and control systems. Measuring in-rush current (the amount of current drawn by a motor during start-up) is another feature incorporated in some clamp meters. We did exhaustive market research, customer interviews and surveys to design an innovative product. Rish Clamp Power, which was launched in December, is a state of the art single instrument with multiple features, giving users value for money,” shares Loveesh Jaiswal, product manager, test and measuring instruments, Rishabh Instruments.
Transmitting readings to mobile devices: Integration of Bluetooth in clamp meters is another important feature introduced by some players. Extech’s EX850 TRMS 1000A AC/DC clamp meter with Bluetooth works with a free Android app to display large, easy to read values for AC/DC voltage, AC/DC current, capacitance, resistance, frequency, diode tests and temperature (type-K and infrared), and can display the readings up to a distance of 10 m. It’s TRMS sensing, low pass filters, capacitance, fast response processors and its unique Amp-Tip function make these Extech clamp-on amp meters the best choice for quick, error free measurements in 600V and 1000V (AMP-330 only) environments.
Wide range of measurement functions: Today, the clamp meter offers state of the art functions. The APPA series of clamp meters offered by Avante Global is capable of measuring 1000V AC/DC voltage which is very useful for UPS and solar power plant applications. The selection of various sub parameters and functions can be done with just the click of a mouse. So, it is possible to offer a wide range of functions on a compact instrument. According to Praveen Kumar Gupta, proprietor, Avante Global Services Pvt Ltd, “Earlier, features like inrush current, THD, harmonics, AC+DC measurements, etc, were available only on bulky and expensive power meters. These features have been added at almost no cost to normal clamp meters. Clamp-on meters have additional functions like measuring power factor, power, THD, temperature, capacitance, phase rotation and diode checks, besides normal features like measuring volts, amps, resistance and frequency, which are available on all clamp meters. These features make clamp meters very useful in almost all electrical maintenance applications.”
Digital Clamp meters: Meco Instruments has introduced new digital clamp meters Model 2502T-auto and 2520THz-auto. With 2000 and 4000 counts respectively, having current range upto 1000A AC and voltage range 750V AC and 1000V DC with the jaw opening size of 52mm. In addition it has features like NCV, temperature, capacitance, frequency, resistance, audible continuity, duty cycle, diode test function etc.
Making a buying decision
The various brands and functions available in the market today may confuse buyers while trying to make the right choice. Customers should first check their application’s requirements and assess the electrical load in their system. A rule of thumb is that if you have variable frequency drives installed on motors, power electronics or semiconductors, you should go in for a TRMS clamp meter, which will give accurate readings on all kinds of loads. For residential applications, an average sensing clamp is an acceptable choice and works satisfactorily. Today’s clamp meters offer additional functions like voltage, resistance and capacitance measurement as well as other user friendly features like inrush current measurement, backlit LCD displays, min-max, and data hold, which can be valuable to customers.
Safety: Clamp meters should conform to safety standards like IEC 61010 and should be tested at independent test labs like UL and TUV. Safety is the one parameter which should not be compromised. Users should remember that buying cheaper low quality products in the market may prove to be so much more expensive in the long run. Safety starts with choosing the right meter that adheres to accepted safety standards for the environment in which the instrument will be used.
Ease of use: A user should select a clamp meter with easy to replace batteries so that the testing is not hampered. An auto-ranging display, which automatically sets the correct measurement range, will eliminate the problem of having to adjust or switch positions while trying to get a measurement when in a tight spot and, hence, save time. Also, one should choose a clamp meter with a large, easy to read backlit display that will perform well in real world conditions.
The specifications trap: Loveesh Jaiswal suggests, “Users should not fall into the typical specifications trap which manufacturers lay before them. They should look beyond features and functions and assess the overall value represented by a meter’s design and application.”
Test probes: Test leads are a means to connect your clamp meter to the unit under test. They are an integral part of the complete measurement system. Poorly made, worn, or underrated test leads can cause inaccurate readings and may pose a serious shock or electrocution hazard if you touch live wires that the meter has read as being de-energised. The quality of test probes is as important as the quality of the meter the buyer selects.
BOXES
Extech’s EX850 TRMS clamp meter
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Non contact IR thermometer design with laser pointer
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TRMS current and voltage
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measurements
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Peak hold captures in-rush currents and transients
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43mm jaw opening for conductors up to 750MCM or two 500MCM
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4000 count backlit LCD display
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Auto ranging with manual range button, data hold, min/max and auto power off
Meco’s 2502T-auto and 2520THz-auto models
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Handy and user friendly
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Auto/manual range selection
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Non contact voltage testing function
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Temperature measurement, frequency measurement (2520THz-Auto)
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Data hold, max (2502T-auto)
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Capacitance (2520THz-auto)
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Auto power off
Metro Q offers Mastech’s MS2208 power meter
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Large dual 6000 count LCD display
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Measures AC voltage, AC current, single phase active power, power factor, passive power, frequency and harmonics
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Data hold, backlit display and auto power off
Rish Clamp Power
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In-rush/peak value measurement
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LPF mode-VFD measurement
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Inbuilt three phase power measurement (balanced/unbalanced)
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Energy measurement
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Measures active, reactive and apparent power, and up to 49th harmonics
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Phase angle, THD, power factor, crest factor
Avante Global offers APPA 136
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Measures up to 1000V AC/DC
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Measures power, power factor, THD, harmonics up to 25th harmonics, phase rotation
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Diode check (shows open, short and good), capacitance measurement
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In-rush current measurement, AC+DC measurement
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Inbuilt torch for working in dark areas (automatic operation with opening of jaw)
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Non-contact voltage detector, best resolution of 0.01V and 0.01A
Fluke’s 381 series remote display
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Wireless technology allows the display to be carried up to 9.04m away from the point of measurement without interference with measurement accuracy
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The removable magnetic display can be conveniently mounted where it is easily seen
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iFlex flexible current probe expands the measurement range to 2500A AC
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CAT IV 600 V, CAT III 1000 V
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Ergonomic design, radio transmitter automatically sets the correct measurement range so the user does not need to change the switch positions while taking a measurement
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Three year warranty, soft carrying case
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Integrated low pass filter and state of the art signal processing
