By Samonway Duttagupta
Multimeters are devices that measure multiple parameters including voltage, current and resistance. These functions make them a common tool in any company involved in electronics. Multimeters are also used for basic fault-finding in electrical circuits, in educational laboratories and by hobbyists.
With the rapid pace of development in electronics, multimeters also need to stay abreast with what is happening in this field as they are one of the most commonly used test and measurement instruments.
The market for multimeters is huge and there are plenty of options available, starting from low cost to high-cost variants. The low- cost options usually include the basic digital multimeters (DMMs) that are used by hobbyists with fewer requirements and those who do not want to invest too much in such equipment. They are used in areas like academics, basic electrical testing and for testing of office electronics, among other functions. The high-cost DMMs, which include both bench-top and handheld variants, are used for industrial purposes—in factories, electronics manufacturing, high-end laboratories and even engineering colleges.
The complexity in the current field of electronics has led to the phasing out of old multimeters. This is because modern electronics devices and systems draw non-linear current and thus have a non-sinusoidal or distorted waveform. In such cases, there are chances that the old multimeters show an average figure that is 35 to 40 per cent lower or 8 to 10 per cent higher than the actual reading. This is where the RMS and TRMS (true RMS) methods come into play. Here, the averaging method is not used to calculate AC current or voltage. Instead, the root means square or RMS formula is used to accurately calculate the distorted waveform readings. This formula is used in most of the modern electronic applications that include solid state electronics, variable frequency/speed drives, motor controls, high-efficiency HVAC systems, phase control dimmers, power supplies and others.
Other multimeters that are trending these days include auto range multimeters, manual range multimeters, and multimeters with the safety categories CAT I, CAT II, CAT III and CAT IV. And there are UL certified DMMs, which are used by industries that require high standards of safety for their equipment and employees.
Latest technological trends
Technologies usually develop in line with the changing needs of users. Multimeters, too, are going through rapid technological changes in tandem with the constantly evolving requirements of the industries using them. The technological trend these days is to provide multiple functions in one instrument. Original equipment manufacturers (OEMs) are currently integrating other instruments with multimeters. Common examples of this include multimeter-cum-insulation testers and multimeter-cum-infrared (IR) thermometers. Besides, there are multimeters with several specialty insulation modes including polarisation index, dielectric absorption and earth bond resistance other than insulation tests, all in the same unit.
As mentioned earlier, the trend is to use safer instruments. According to T.P. Singh, country manager, India –sales (instruments), FLIR Systems, CAT IV safety rated multimeters are the most common devices offered by reputed manufacturers these days. Also preferred are the DMMs that come with the internationally accepted IP 67 protection marking enclosures that are dustproof and waterproof.
All-in-one devices are the way forward
Today, companies look to get the maximum benefits from every little investment in production resources. Multi-function multimeters require buyers to invest less and get more out of the instrument while avoiding additional expenses on other instruments. An example of this would be the latest multimeter launched by Kusam-Meco (Kusam Electrical Industries Ltd), called KM 878, which is a true RMS or TRMS DMM with 24 functions and 79 ranges – all in one device. In fact, the company claims that the number of functions offered by this multimeter is its unique selling proposition (USP). The device’s protection level is at CAT IV 1000V AC and DC and CAT III 1000V AC and DC. Transient protection is 8KV. Some of the major functions include DCV, VFD, ACV, AC mV, DC mA, ACV, DC mV, AC mA, insulation resistance (50/100/250/500/1000V selectable), Hz line frequency temperature, audible continuity test, earth bond resistance and capacitance diode testing.
Another example of such versatile devices is the IM75 multimeter recently launched by FLIR Systems. Apart from being an advanced multifunction DMM, it is also a premier handheld insulation tester for installation, troubleshooting and maintenance professionals. Insulation tests can be performed instantly, continuously and over a timed duration for in-depth assessment. The product comes with a limited lifetime warranty. Its USP is its specialty insulation mode that includes polarisation index, dielectric absorption and earth bond resistance measurement along with other precision multimeter functions.
Better interfaces and greater accuracy
Tektronix India has recently launched Keithley Instruments’ latest DMM7510 7½-digit graphical sampling multimeter. The company claims that this digital multimeter is the first of its kind in its class. It integrates a highly accurate DMM, a digitiser for waveform capture and a capacitive touchscreen user interface. The model has been designed to give users confidence in the accuracy of the results that are produced and the ability to explore measurements further. It has an intuitive touchscreen operation.
This multimeter provides a new and intuitive experience in DC source measure testing, enabling users to do more in less time. It is also capable of providing source and measure voltage, current and resistance, thus ensuring a better user experience. Additionally, it provides I-V system, curve tracer and semiconductor analyser capabilities at a low cost.
For in-depth testing, engineers need to capture small signals at a higher accuracy and faster speeds than traditional DMMs can provide. DMM7510’s intuitive operation and high speed digitiser allow it to address a wide range of test applications, including device characterisation, debugging and analysis, and production tests. That is why it is used in research labs and universities.
Picking the best
Electronics Bazaar conducted a small survey across the industry, which included key test and measurement companies manufacturing multimeters and their users, on how to select a multimeter. Here are the findings of the survey:
1. Determine the specific tasks at hand for which you need a multimeter. This will keep you away from selecting a multimeter with wrong frequency features or improper frequency ranges.
2. Determine the kind of environment for which the multimeter is needed. If it is for industrial use where the devices will be used under rugged conditions like in a factory, a heavy duty, waterproof and dustproof multimeter will do the job for you. If delicate and precise measurements need to be done indoors, then a basic, feature-heavy yet typical DMM is good enough.
3. Determine the mobility required for the multimeter. If it needs to be carried around at all times, then a handheld multimeter is a good option; else, a bench-top one will do the job for you.
4. To make a worthwhile investment on a multimeter, you will need to gauge whether the device would still be useful three years from the time of purchase. Features like functions and ranges should be advanced enough to remain relevant over a long period.
5. Carefully check the terms for pre- and after-sales service.
6. Certifications and standards with regards to safety should be taken into consideration.
Latest In The Market
Keithley Instruments’ DMM7510 7½ from Tektronix India
- DC voltage: 1000V
- Resistance: 1Ω to 1GΩ
- Capacitance: 1nF to 1000μF
- Frequency: 60mV to 600mA
- Diode test: 10V
USP: First of its class to integrate a high accuracy digital multimeter, a digitiser for waveform capture and a capacitive touchscreen user interface
IM75 by FLIR Systems
- Insulation resistance: 4M to 20GΩ (±1.5%)
- Insulation test voltages: 50V, 100V, 250V, 500V and 1000V (±3.0%)
- DC voltage: 1000.0V (±0.1%)
- AC voltage: 1000.0V (±1.5%)
- VFD AC voltage: 1000.0V (±1.5%)
- Earth bond resistance: 40Ω to 40KΩ ±1.5%)
- Capacitance: 10mF (±1.2%)
- Frequency: (ACV) 40kHz +/- 5 digits
- Diode test: 2V (±1.5%)
- Continuity: 400.0Ω (±0.5%)
USP: Specialty insulation modes that include polarisation index, dielectric absorption and earth bond resistance measurement along with precision multimeter functions
KM 878 by Kusam-Meco (Kusam Electrical Industries Ltd)
- Insulation resistance: 3MW to 25GW
- Insulation test voltages: 50V, 100V, 250V, 500V and 1000V
- DC voltage: 1000V
- AC voltage: 1000V
- VFD AC voltage: 600V
- Resistance: 600W to 60MW
- Capacitance: 30mF
- Frequency: 60mV to 600mA
- Diode test: 2V
- Continuity: 2W to 20W
USP: The number of functions offered by this multimeter (24 functions and 79 ranges)
Advice from the industry
“Multimeters have been evolving as high-end electrical and electronic testing equipment to serve complex testing needs. Today, multimeters incorporate a higher level of integration, connectivity and advanced features.”
Naresh Narasimhan, country marketing manager, Tektronix India
“A multimeter is an indispensable instrument in the field of electronics — just as doctors cannot perform their duties without a stethoscope, electronics engineers cannot do their work without the aid of the multimeter. As most multimeters are imported, it is difficult to gauge the exact market size, but it is growing at 25 per cent in a year.”
Chandmal Goliya, director, Kusam-Meco (Kusam Electrical Industries Ltd
“New trends help users as they get a safe product. Also, these days, instead of carrying multiple instruments around, they can carry fewer instruments. With precision multimeters becoming more affordable, the results of the tests done using these devices have become more dependable.”
T.P. Singh, country manager, India – sales (instruments), FLIR Systems