Instrument companies have found that HVACR technicians are demanding instruments that offer a more compact design that require less space, offer greater safety, and are easy-to-use when measuring the large number of parameters required by their jobs. The response by some manufacturers has been modular design.

Modular design enables field service technicians to carry less equipment, test a wider variety of parameters, and, because all the test modules work the same way, perform most tests more easily.

Modular instruments, introduced in the late 1980s, offer the HVACR technician a convenient and cost-effective way to measure a wide variety of parameters. The modular system gives a technician the ability to make most measurements necessary for his job by providing a series of dedicated test heads that fit onto a digital multimeter.


Fieldpiece Instruments (Brea, Calif.) developed a line of modular instruments designed specifically with HVACR technicians in mind. According to company President Rey Harju, "One of the constant complaints we heard from the field was how much gear technicians had to lug around. Some would shortcut their diagnostic testing if the proper instrument wasn't at hand, and that's never a good idea. Modular design solved the problem."

The company's products feature special-purpose heads that slide onto a specially built, general-purpose digital multimeter (DMM). The heads are dedicated measuring units, smaller and less expensive than their predecessors. They also developed a data logger handle to record test results, and an electronic handle that converts any of the heads into stand-alone instruments.

Once the company had developed the test heads, it started looking for ways to offer them to the field service technicians. There are now five Fieldpack kits in the line, four of them packaged in a soft-sided bag the size of a briefcase and the other in a smaller version. A tech could start with a smaller kit and gradually upgrade, the company said.

Versatility is key for technicians, who understandably want to carry as little as possible while still having the right instruments to make a correct diagnosis. One current instrument, for example, uses three instruments as the foundation for the kit (Fieldpiece Model HS35K31G): the HS36 auto-ranging DMM stick meter, a data logger, and an electronic handle. Each of them accepts every one of the snap-on accessory heads that measure air velocity, air temperature, relative humidity, wetbulb temperature, dew point, infrared temperature, carbon monoxide, voltage, ac current, gas pressure, static pressure, vacuum (for evacuating a system), superheat/subcooling, and microamps for flame rectifier diode circuits. Additional thermocouples include a pipe clamp thermocouple for taking suction line temperatures, a wetbulb thermocouple with a "sock" and alligator clip, and a beaded thermocouple with an alligator clip.

The stick meter's auto-ranging feature automatically changes range for the best resolution, the company said. For hard-to-reach measurements, the technician can remotely connect an accessory head by removing the probe tips from the leads and connecting to the head.

"This feature eliminates a host of problems for field technicians," said Harju. "There are so many situations where it is difficult, if not impossible, to insert an instrument, make the appropriate contact, and read the result. By remoting the instrument body from the modular head, the technician only needs to insert the head into the area to be tested and keep the instrument body separate for easy reading and recording.

"This feature is particularly useful when measuring current in tight spots where there are a lot of active wires present," he continued. "By remoting the clamp head and placing the meter nearby, it reduces the bulk."


"We were looking for something to take superheat and carbon monoxide measurements," said Tim Bridge, service manager for Butler Mechanical Services, Cincinnati. "We went into Lute Supply in the city and they had this Fieldpack on display, the big one. I asked what it was and the guy showed me."

The company bought it. "We've used it on every job since we got it and we've used every feature at one time or another," said Bridge.

"It's great to have virtually every instrument you need in a small bag," said Scott Owen, HVAC instructor at Northeast Community College in Norfolk, Neb. "I tell my students they would need a large dolly to carry the equivalent."

"We've taken into consideration that a technician may be happy with his current meter," said Harju. "So we designed the heads so they could be used with any meter using industry standard jacks." The company's Phoenix Series is a line of three clamp meters. It was introduced in the fall of 2005 by UEI (Beaverton, Ore.).

"We decided to make a clamp-on multimeter specifically for HVAC field service people so we asked them what they wanted," said Bruce Baker, national sales manager for UEI. "They told us they wanted a clamp meter that could measure more than just basic volts and current parameters, so we built it for them. Actually we built three, the Phoenix I, II, and III."

Phoenix I, designed for general use, measures ac, motor, and line current; supply, control, or system board voltage; motor run or start faults; circuit continuity or specified resistance; motor in-rush; and frequency of variable-speed drives and supply power. Phoenix II, designed for HVAC use, also measures temperature, checks for live wires, and can display two readings simultaneously. Phoenix III includes all of those measurement capabilities and adds true RMS. All three feature a built-in flashlight for working in dark areas.

The clamp head of the meter can be removed and replaced with the modular hook. Once added, the hook increases the technician's reach and enables him to work in confined spaces with ease, singling out the correct wire and hooking it with the tip, the company said. Once hooked and isolated, the wire's current can be easily measured.

"It not only makes the task safer for the technician," said Baker, "it also makes the job easier and faster."

As more manufacturers turn to field service technicians for input in developing new equipment, safety, convenience, and efficiency are bound to improve.

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Publication date: 09/11/2006