Safety Tip #2: Don’t risk CAT IV areas without the right leads

What’s the difference in test leads?

Not all test leads are created equal. It’s very common to accumulate test leads over the years and mix them up with the newer, more robust leads available today. Test leads, just like the testers themselves, have been upgraded to meet the new safety standards established for today’s electrical environments. These standards require that the insulation between the test lead conductor and your fingers have the minimum distance to stand off the hazards that exist in the environment in which you are working. There should also be a finger guard on the outside of the probe that establishes the proper distance between your fingers and the exposed metal parts of the probe. These distances and insulating ratings have been predetermined for each installation category and voltage rating.

What’s the difference in test leads?

Not all test leads are created equal. It’s very common to accumulate test leads over the years and mix them up with the newer, more robust leads available today. Test leads, just like the testers themselves, have been upgraded to meet the new safety standards established for today’s electrical environments. These standards require that the insulation between the test lead conductor and your fingers have the minimum distance to stand off the hazards that exist in the environment in which you are working. There should also be a finger guard on the outside of the probe that establishes the proper distance between your fingers and the exposed metal parts of the probe. These distances and insulating ratings have been predetermined for each installation category and voltage rating.

Another characteristic to watch for is the amount of current test leads can safely handle. In the previous example, the Fluke 170 and 180 Series products are fused to a maximum current of 10 A. When measuring current using test leads with a current rating less than 10 A could cause the test leads to become overheated. This in turn could cause the insulation to melt and compromise the safety rating of the leads. Again, discard all leads that have discoloration or appear to have melted insulation and replace them with new ones.

Category IV ratings

Recently the International Electrotechnical Commission (IEC), an organization that develops safety standards, defined the standards for Category IV environments. This environment includes overhead power lines, underground power lines, and service entrance power. These are environments where electricians make measurements every day. In order for you to make measurements in these environments safely, Fluke has upgraded most of its test lead products to meet the new CAT IV standards. If you find yourself making measurements in these areas and have an older set of leads, you might want to consider replacing them with leads that are clearly marked as rated for CAT IV.

Safety Tip #1: Choosing the correct fuse for your tester can avoid hidden dangers like serious burns & possibly even death

Why does a tester need fuses?

There are a variety of testers on the market, from simple voltage detectors to highly sophisticated digital multimeters (DMMs). Testers that make voltage measurements have a high input impedance that makes an overcurrent condition unlikely. As a result, voltage measuring inputs are generally not designed with fuse protection but with overvoltage protection. But if that same tester is designed to also measure current, fusing is required. Current measuring inputs usually employ a simple shunt through which the measured current flows. This shunt’s resistance is on the order of 0.01 ohms. Add to that the resistance of the test leads (approx. 0.04 ohms), and you have a short of less than 0.1 ohms. This resistance is adequate when you place this short in series with another load to measure the circuit’s current. But it’s an altogether different story when you place this circuit across a voltage source, say the plug outlet in your living room.

This is an all too common mistake made by people measuring both voltage and current. After making a current measurement with the test leads in the current input jacks, the user tries to make a voltage measurement forgetting the leads are in the amps jacks. This effectively places a short across the voltage source. Years ago, when analog meters were the only instrument for making these measurements, this mistake pretty well destroyed the meter movement (the needle wrapped around the top peg), not to mention the internal circuitry. To protect against this common occurrence, meter manufacturers started putting a fuse in series with the meter’s test lead jacks, for an inexpensive and effective solution for a very simple mistake.

Today, most manufacturers still design their testers with fuse protection in the current measuring circuits. As technology has moved forward, the science of fuse design has progressed as well. Although understood by people who build testers, the full impact of fusing is little understood by most tester users. When you make that simple mistake of putting voltage across the current jacks and blow the fuse, you’re at first thankful you didn’t wipe out the meter. But you may then become annoyed with the fact that you have to hunt up a new fuse and replace it before making your next current measurement. Even more frustrating is when you share meters with other people in your shop and someone else blows a fuse and puts the meter away to have the problem discovered by an unsuspecting user.

Using the proper fuse

Specially designed “high-energy” fuses are designed to keep the energy generated by such an electrical short within the fuse enclosure, thus protecting the user from electric shock and burns. These high-energy fuses are designed to limit the length of time the energy is applied and the amount of oxygen available for combustion. Fuses can not only be designed to open at a specified constant current, but at an instantaneous high current as well. This high current is specified as “minimum interrupt current.” Fluke uses fuses with a minimum interrupt rating of 10,000 and 17,000 amps in their testers.

If you take a CAT III 1000 V meter with the test leads in the amps jacks, you will have a series resistance of approximately 0.1 ohms (0.01 for the shunt, 0.04 for the test leads and 0.05 for the fuse and circuit board conductors) between the leads. Now when you accidentally place the leads across a 1,000 volt source, by Ohms Law you will generate a current of 10,000 amps (E/R=I, 1,000/0.1 = 10,000). You want a fuse that will break that current and do it quickly.

In addition to the specially designed fuse element, the high energy fuse is filled with sand. The sand will not only help absorb the shock energy created by the exploding element, but the high temperatures (up to 10,000 °F) generated by the energy will melt the sand and turn it to glass. The glass coats the element and smoothers the fireball by cutting off the available oxygen, keeping you and the tester safe from harm. As you can see, not all fuses of the same amperage and voltage rating are the same. For your own safety you need to be sure the fuses you use are the ones the engineer designed into the tester.

Always refer to the tester’s manual, or check with the tester manufacturer to ensure you have the correct fuse. You can always get replacement fuses for Fluke testers by ordering the part number listed in the tester’s manual. Your safety is worth much more than the money it takes to purchase the proper fuse for which the tester was designed.

ADMET 2011

Fluke introduces ScopeMeter® 190 Series II Portable Oscilloscopes engineered for harsh industrial environments

Four-channel scopes go anywhere there is trouble

Fluke Corporation, the global leader in portable electronic test and measurement technology, has introduced the Fluke ScopeMeter® 190 Series II handheld portable oscilloscopes, the first four-channel scopes designed for harsh industrial environments.

These new portable scopes are the first safety rated for CAT III 1000 V / CAT IV 600 V environments. The four input channels are fully isolated from each other to perform differential floating measurements, a critical consideration for troubleshooting fixed-installation three-phase power electronic devices like variable speed motor drives.

The Fluke ScopeMeter chassis is sealed from the environment with no cooling slots or fans to expose the instrument. It carries the International Protection (IP) -51 dust and drip proof rating so it’s tough enough to use safely on the factory floor and in the field. While most high-performance oscilloscopes are not designed to withstand dirty and harsh environments, the Fluke ScopeMeter is built tough to deliver accurate results where ordinary portable oscilloscopes dare not go.

The Fluke 190 Series II oscilloscope meets the growing need for four-channel portable oscilloscopes in industrial environments. Power electronics are used increasingly in solar and wind energy generation and to maximize efficiency or reduce power consumption especially in heavy-duty electro-mechanical applications. With the new Fluke 190 Series II ScopeMeter, users can see more and fix more using all four channels.

Their fast sampling rate, up to 2.5 GS/sec and 400 pico second resolution, helps users capture electrical noise and other disturbances to diagnose exactly what is going on. With100 MHz and 200 MHz models, they deliver the bandwidth needed to cover both today’s needs, and tomorrow’s. With four channels, users can inspect input signals, output signals, feedback loops, or safety interlocks simultaneously to solve problems like:

• Signal amplitude or shape variations, induced noise or disturbances across critical

circuit nodes.

• Signal timing measurements and synchronization issues.

• Attenuation, fluctuation, drift as a result of impedance issues or environmental impacts.

Four channels are indispensable in testing variable speed motor drives and inverter power electronic technology used in green energy generation and transportation applications. Users can:

• View and measure harmonics, transients, and loads in three-phase power systems.

• Troubleshoot dc to ac converters for faulty insulated-gate bipolar transistors (IGBTs)

and control circuits.

• View and measure pulse width modulated waveforms (PWM) for reflections and

transients.

These new test tools are convenient and user-friendly. New, high-performance Li-ion battery technology keeps the Series II ScopeMeter on the job for up to seven hours. An external charger and easy-access battery door makes it simple to swap batteries and extend usage. Two USB ports, electrically isolated from measurement input circuits, make it easy to capture and share waveforms. Users can conveniently store data to a USB memory device or easily connect to a PC via the USB port and transfer waveforms or screen images for data analysis or archive.

Basic Power Quality Measurements On The Go With The Fluke 345

Fluke Corporation, an industry innovator in compact, professional electronic test tools has announced the re-launch of Fluke 345 Power Quality Clamp Meter, designed as a tool for servicing and commissioning electronic switching loads including variable frequency drives, electronic lighting and uninterruptible power supply (UPS) systems. Combining the functionality of a power quality meter, oscilloscope and data logger, the Fluke 345 features a convenient clamp-on design for measuring the most common power quality parameters. It features a colour display for viewing measurements in real time, and can log data to memory for analysis with the included Power Log software.

The Hall effect measuring clamp of the Fluke 345 enables users to take ac current measurements up to 1400 A rms and dc current up to 2000A – without disconnecting the load. It features a switchable low-pass filter, enabling users to make effective measurements on variable frequency drives and other electrically noisy equipment.

The recording function of the Fluke 345 captures minimum, maximum, and average values for a quick view of events as they occur. For intermittent problems or performance testing, the logging mode can be used to capture measured values of voltage, current, and power with average periods from one second to 15 minutes. Logged data can be reviewed on the instrument, or downloaded for further analysis and report generation, using the supplied Power Log software.

The Fluke 345 complies with the stringent 600 V CAT IV / 1000 V CAT III safety standards. It measures V, A, Hz, CF, THD, DF, W, VA, VAR, kW and Power Factor even on distorted waveforms. Other useful features include a three-phase power mode for making a quick check on a balanced three phase circuits, an inrush mode for troubleshooting tripped circuit breakers, and dc ripple measurement capability to assess load effect.

Fluke introduces testing up to 10 kV with the new 1555 and redesigned 1550C insulation testers

Ideal for testing high voltage equipment

Fluke Corporation, the global leader in portable electronic test and measurement technology, has introduced the new Fluke 1555 and redesigned Fluke 1550C insulation resistance testers designed for a wide range of diagnostic and predictive maintenance programs.

These testers offer digital insulation testing up to 10 kV (Fluke 1555), making them ideal for testing a wide range of high voltage equipment including switchgear, motors, generators and cables.

Fluke insulation testers can now conduct the entire range of test voltages specified in IEEE 43-2000 with a best in class, three year warranty and CAT III, 1000 V, CAT IV 600 V safety rating. With measurement storage and PC interface, the Fluke 1555 and 1550C are perfect tools for long term equipment monitoring.

Features of the Fluke 1555 and 1550C include:

· Test voltages up to 10 kV provides solutions for all applications.

· CAT III 1000 V, CAT IV 600 V safety rating.

· Warning function alerts the user that line voltage is present and gives the voltage reading up to 600 V ac or dc for increased user safety.

· Selectable test voltages in 50 V steps from 250 V to 1000 V, and 100 V steps above 1000 V.

· Measurements can be stored in up to 99 memory locations, with each location assigned a unique, user-defined label for easy recall.

· Long battery life performs more than 750 tests between charges.

· Automatic calculation of Dielectric Absorption (DAR) and Polarization Index (PI) with no additional setup.

· Guard system eliminates the effect of surface leakage current on high-resistance measurements.

· Large digital/analog LCD for easy viewing.

· Capacitance and leakage current measurement.

· Ramp function for breakdown testing.

· Resistance measurements up to 2 TΩ.

· Timer settings up to 99 minutes for timed tests.

· Best-in-class three year warranty.

FREE 500GB External Hard Drive on purchase of Fluke 43B Power Quality Analyzer

Click Here to know more