Web applications, or "Apps", are all the rage. Running on a smart phone, they represent an intersection of the internet and a handheld touch panel. They provide a combination of fun and functionality - many of most popular Apps are games. They are fast and easy to use, contain a lot of intelligence around a specific task, and deliver fast answers. For example, the Carbon Footprint Calculator asks you to enter miles driven, airline trips taken and electrical / natural gas consumption, then quickly shows how many trees are required to offset your presence on the planet.

It turns out that Fluke has been packaging Apps for years in the form of specialty Digital Multimeters. They are fast and easy to use, and contain a ton of intelligence around Ohm’s Law, E= I x R. The smarts reside in firmware rather than software, and the platform is a rugged handheld DMM versus a phone. However, the outcome is the same - fast answers.

Here are four applications matched with a task-specific DMM to deliver the power of a modern App:

1. For Predictive Maintenance, the 289 Industrial Logging Multimeter offers 0.025% basic DC accuracy, 100 kHz bandwidth and graphical display to support sophisticated logging and Trend Capture.
2. For HVAC repair, the 116 HVAC DMM measures temperature and micro amps, plus offers selectable low input impedance often required with HVAC system components.
3. For Process Calibration, the 789 ProcessMeter sources and measures 4 to 20 mA control signals, while simultaneously reading in mA and % of span. The meter provides Loop Power, manually or automatically steps in 25% of span, and includes a 250 ohm HART resistor.
4. For automotive troubleshooting, the 88 Series V Automotive Meter offers millisecond pulse width measurements for fuel injectors, inductive pickup for RPM readings and 20 A current measurement for modern automotive applications.

Audition one of these Fluke Apps today to see the power and speed they can bring to your daily workload.

Bio: Rick Pirret recently retired from Fluke following 30 years in product design and marketing. Previously, he was with Bell Labs for 10 years in product and facility design. Rick studied mechanical engineering at Cornell and Stanford, and completed an MBA at Seattle University. Over the years, hobbies have included scuba diving, white water canoeing, flying, motorcycling, and bicycling. More recently, Rick likes to be outdoors in the Cascades Mountains or on-track in a BMW.

The process: Weighing and dense phase conveying of batches of grain.
The scale: Mettler Toledo 8510
The meter: Fluke 199B/S ScopeMeter® test tool

A vessel on three load cells is filled from a hopper above with around 1500 pounds of grain, depending on the recipe. The slide gate metering the grain is controlled by a PLC-5 based on weight read from the scale terminal. The vessel pressurizes and the grain is forced out the bottom into a transport pipe, sending the grain across the building to processing. When empty, a blower purges the line.

We were getting irregular batch weights. The weight indicated on a Wonderware terminal would occasionally jump low. The weight shown on the scale display was stable. The 4-20mA signal from the scale to the PLC seemed stable with a Fluke 179 Digital Multimeter. Another signal connected to the same channel seemed stable, but that was done with the system idle. Another channel then another input module was tried. Any problem could not readily be seen looking at raw data in RS Logix.

I requested and got the CS20MA for my new toy, the Fluke 199B. I connected in series and recorded a batch. The first batch recorded showed no obvious signs of trouble. Filling and discharging weight seemed smooth although the empty current was a little low.

The next batch was a scope record:

That sure didn't look right. The noise at the end is the blower running but why was the signal 3-7mA thick?

Zooming in on the noise:

I consulted the scale manual. The interconnect diagrams on pages 58-59 showed me that the analog output module on the back of the scale got 120VAC in and the loop power originated on board. Page 55 shows the analog board. C8 and C10 are 470uF 35V. C9 between them is 47uF 25V. Radio Shack actually stocked these caps in 35 V. The 47uF C9 was the culprit. I replaced all three caps for four bucks.

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