The portable, battery-powered unit provides a minimum of eight hours of use on one charge.
did, however, develop concerns about reliability, stemming not from the
transducers themselves, but from the device employed in testing the
“We were using a little static
pressure source, basically a hand-driven pump with fine adjustment, and
a micromanometer,” says Hampton, who maintains the company’s
calibration records as well as writing and updating standard operating
procedures for testing. “But that system had definite shortcomings. The
most glaring is that if the system had a microleak—which it frequently
did—you could not be assured that you were getting a truly accurate
reading.” He explains that there are a number of brazed and soldered
joints on the copper lines from the unit under test to the calibrator.
“This allows for the possibility of microleaks that will not be
detected during testing because the source of the measured pressure is
a constant source, such as a blower moving air. However, these leaks
would affect calibration with the static pressure source being used;
this effect would be significant because the measurements are 5 in. of
water or lower. What’s more, it meant that we could not maintain the
calibration point, so recalibration was often necessary.”
the old device was also time-consuming and labor-intensive. “Most
times, it ended up being a two-man job, one controlling the pump and
the other reading the instrumentation,” Hampton adds. “Plus, it would
take 30–35 minutes to run through three test points.”
saw a compelling need to rectify the issue. At the time, the company
was in the process of replacing its existing low-pressure transducers
with transducers from Setra Systems (www.setra.com), a designer and
manufacturer of pressure measurement devices located in Boxborough, MA,
“We were updating our transducers from
Setra a few at a time,” recalls Hampton. “The process had actually
started about a year or two before we pinpointed our calibration
problem. We were very satisfied with the new transducers, so we decided
to see what other products the company offered. They were a known
quantity to us.”
spotted a Web banner for Setra’s line of calibrators and felt it was
well worth checking out. In fact, NORDYNE performed a thorough review
of the product line and its capabilities, and ended up choosing Setra’s
Micro-Cal Model 869 ultralow-pressure documenting calibrator. The
device is used exclusively to regularly calibrate the 30+ low-pressure
transducers (half of them are now from Setra, with plans in process to
replace them all).
The calibrator is
specifically designed for air-handling processes needing portability,
high accuracy, and low-pressure documenting calibration to certify
pressure needs. It does so by performing calibration checks on sensors
with accuracies as high as 0.00025 in.W.C. It is a battery-powered unit
providing a minimum of eight hours of operation, while giving a
pressure reading accuracy close to 0.0001 in. W.C., with fast, stable,
and repeatable pressure generation better than 0.0003 in. W.C. With
recorded calibration times as fast as 5 minutes per unit, users see
time-saving benefits, as well as substantial cost savings for service
and installation time.
The calibrator supplier
says its accuracy is far higher than the results achievable in
traditional laboratory benchtop calibration units that are accurate
only to 0.0004 in. W.C. and require at least one full hour to run
calibration checks on one unit.
Nordyne did look at calibrators from other suppliers and was intrigued by one unit in particular.
other calibrator caught our attention because it was about half the
price of the one offered from Setra,” says Hampton. “It had a nice
low-pressure source, and we actually got a model to experiment with.
But it turned out to be a source only; it provided no onboard control
or data log capability. Despite the lower cost, it was not going to be
sufficient for our operation.”
The ease of
control and simplicity have been real benefits, according to Hampton.
“I conduct virtually all of the calibrations in addition to my other
duties,” he says. “So I needed something that was quick and easy, and
would not cut into the time I’ve allotted for my other
responsibilities. Typically, the Setra 869 allows me to do a
calibration in about five minutes, versus the 30 or so minutes with the
He says that 25-minute saving per
procedure may not sound like much by itself, but after several
procedures it adds up to real time saving. Another important resource
saving comes from the ability to perform calibration unassisted.
Hampton no longer needs to involve a second employee in a calibration
he is performing.
He did train another staffer on the system, however. “After just five minutes of training,
he was already proficient in how to register calibration points,”
The company is also currently supporting a test station in a gas furnace lab that makes use of 11 low-pressure transducers.
of these readings can be as low as 0.25 in. of water, such as the heat
exchanger intake pressure,” says Hampton. “This makes the calibration
method even more critical than that of the psychrometric rooms.”
of the transducers is calibrated yearly to ensure optimal performance.
By doing so, NORDYNE can be confident that the transducers used to
ensure equipment performance are providing the most accurate readings