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At last, an affordable thermocouple calibration unit. (Tools for Environmental Health).

Validation of thermocouple probes is vexatious at best, whereas calibration is just not done. Here is the problem: The thermocouple kit we use for hazard analysis critical control point (HACCP) audits has several different Type K probes that measure the temperatures of different environments; all the probes are connected to one instrument, as needed. For instance, the refrigerator and oven probes measure air temperature; the deep-fat-fryer and dishwasher probes measure temperatures of liquids; the griddle probe measures temperature on a relatively dry, solid surface; and the needle probe measures temperatures of both liquid and semisolid foods. Validation has always been associated with the probe's geometry. Can a single validation tool be applied to probes used in air, in liquids, and on solids? To do a credible job, we would feel more comfortable validating the probes according to their intended use, but this becomes a logistical nightmare. You see the problem?

We do the best we can with what we have. At the least, we can validate the needle and dishwasher probes with relative assurance using our temperature-standard thermometer in the same manner we calibrate our dial thermometers. For the air and solid probes, we have to rely on the instrument's factory calibration and try each probe at ambient conditions before we take the kit into the field. If all of the probes read the same ... we accept that the instrument and probe are synchronized and functioning as intended, This arrangement does not necessarily instill a feeling of confidence.

About four months ago, we received a flyer from Dwyer Instruments, Inc.,[sup.*] listing the most recent additions to its instrument catalog. One instrument in particular piqued our interest- the Model CAlO Digital Thermometer and Calibrator.

The Cal0 has a unique design, and without its ability to source output values and measure Type K thermocouples, it would still be worth consideration. The top of the unit has four standard Type K female mini-connectors: Two are marked output and are used to calibrate both thermocouples and Type K connectors; the other two are for input and are marked T1 and T2. These input connectors can accommodate two temperature-taking probes simultaneously. Although we have not had an occasion to use this latter feature, I am certain that it would come in handy during a HACCP audit. In addition, the unit features a data-hold and backlight button, a max-registering function, a high- and low-resolution button (0.1[degrees]C/F and 1.0[degrees]C/F, a large calibration-output knob, and two smaller knobs for course and fine adjustment. The display is large and easy to read. As a kit, the unit includes a 4-inch Type K bead wire temperature probe, a double male-connector calibration cable, and a standard 9-volt battery.

As good as this Dwyer instrument is, the instructional manual that comes with it is equally bad. The one-page manual provides the usual data, including safety warnings, specifications, environmental operating parameters, and a general description of the unit; however, operating instructions are woefully lacking. The calibration probe, which comes with the unit, is not listed, nor are the abbreviations referring to it defined in the instructions, Neither background-information data on the electronics or principles of operation nor descriptions of the applications and range of use appear in the manual. Warranty information is nonexistent, as are the manufacturer's name, address, and telephone number. I guess the nice folks at Dwyer assume one knows all about the instrument before buying, and woe to the individual who loses the purchase receipt.

We actually had to play with the CA10 and use a trial-and-error method to see how it worked as a calibration device by sequencing the K-type probes and the other instrument we wanted to validate. Needless to say, we did not initially use it on any unit we valued. Nonetheless, once we got the "hang of it," we found this instrument to be a rapid and handy tool for ensuring the accuracy and operation of our field thermocouple thermometers and Type K probes.

In processing the order for this instrument, we found that Dwyer does not exactly value its customers. The flyer featuring this instrument gave its price as $159; we made the purchase by telephone using a credit card. When the instrument arrived, we received with it an invoice for $180 that included $11 for shipping and handling. We contacted customer service about the discrepancy--another toll call--and were informed that prices were subject to change without notice, a fact that was conveniently omitted from the company's flyer, as was any mention of the excessive shipping-and-handling surcharge. In all fairness, we must add that Dwyer did refund the balance for the unit, but it would not capitulate on the shipping charge. This is not the first time this has happened to us with this company Since Dwyer makes so many practical and unique instruments for our profession, however, we do not want to write the company off our preferred-vendor list. Therefore, our advice in dealing with Dwyer is to confirm the tot al price by phone and send a check along with your mail order.

Postscript: We are still quite satisfied with the unit's capability and performance.

Inspection Tip of the Month

Need to confirm the pH of sushi rice? Try using a soil pH kit. These kits are generally available in lawn and garden shops and use a process that saturates the soil sample with an indicator solution. The color of the liquid that has passed through the soil is compared with colors on a color-comparator chart, thereby indicating the pH. Sushi rice makes an ideal medium for this simple field test.

(*.) Dwyer Instruments, Inc., 102 Highway 212, P.O. Box 373, Michigan City, IN. Telephone: (219) 879-8000. Web site: <>.
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Article Details
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Author:Balsamo, James J.
Publication:Journal of Environmental Health
Article Type:Brief Article
Geographic Code:1USA
Date:Mar 1, 2002
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