Calibration, Calibration Logs, and the Check-Temp.

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Calibrating our bimetal thermometers and validating the accuracy of our electronic probe thermometers has always been a chore. Not that we are complaining, but this time-consuming task is an absolute necessity if we are to be accurate, fair, and impartial in enforcing the most important of the food regulations. With a lot of practice, it still takes us a minimum of one-half hour to set up a proper two-point calibration/validation with our temperature-standard thermometer--even though we have two of everything and can complete the tasks (both hot and cold) simultaneously. We are also convinced that temperature validation and recalibration is a "must do" each time that we go back into the field. Our thermometers are subjected to a battery of insults, including temperature extremes, both on the job and during transport--in the case of the bimetal thermometer, we constantly grab it by the bezel, its only moving part. It is, therefore, no small wonder that with use all bimetal thermometers get out of calibration. We often wonder how many sanitarians actually calibrate their thermometers. In some of the institutions we visit, perfectly good food is destroyed because of an inaccurate thermometer. In fact, in the course of our travels, we have found bimetal thermometers that deviate from the actual temperature by as much as [+ or -]8[Degrees]F.

The accuracy of our instruments and verification of calibration have been responsible for our clients winning a number of lawsuits. It started during the course of a discovery inspection, when we noted the discrepancy between the opposing expert's temperature readings and ours. Our "calibration log" and the description of our techniques won the day in court. As a result, we have since become rather dogmatic about maintaining a detailed "calibration log" on all our instruments. The log is kept in a hardbound notebook, with enough space at the bottom of each day's entry to include a notarized statement in the event that we have to present these data in court or at a deposition. The effort to ensure that our instruments are accurate is time well spent. Needless to say, though, anything that would make the job easier would be most welcome.

At NEHA's last Annual Educational Conference, the Tel-Tru Manufacturing Company [*] introduced the Check-Temp Calibrator. These units are designed to quickly and easily verify food service and laboratory thermometers with uncanny accuracy (within [+ or -]0.2[Degrees]F). Four models are available: three go by the name Check-Temp and have a single set-point (40[degrees], 140[degrees], or 160[degrees]F) with the model number corresponding to the temperature. The fourth model is the Check-Temp II, with two set-points (40[degrees] and 160[degrees]F). We were given the Check-Temp 160 and the Check-Temp II as loaners for evaluation.

Each of these units consists of a stainless steel box measuring about 3 by 7 by 11 inches and weighing approximately 9 pounds. The face of the unit has a port into which the thermometer probe is inserted, a green "ready" light, and an on/off rocker switch with a red power indicator. Operation is very simple. Plug the unit in, turn it on, wait approximately eight to 10 minutes for the green "ready" light (only three minutes with the 40[degrees]F model), insert the thermometer probe in the port, and that's it. With the Check-Temp II, we found that it takes approximately five minutes to go from high to low, or low to high temperature. All units have built-in circuitry to warn if the unit is more than 1[degrees]F out of calibration,

Our Check-Temps came with a high-density plastic friction wrench that fits nicely over the bezel of both 1-inch and 2-inch thermometers. The insertion port is configured to accept the adjustment nut located under the dial. So, when the handles of the wrench are squeezed, the bezel is easily turned and set to the temperature specified by the unit. Bingo! Your thermometer is calibrated. We found that we could calibrate all of our stem thermometers, as well as validate most of our electronic thermometers with K-type probe connections, in less than 15 minutes--this is truly a time-saving device.

Each unit comes with a signed Certificate of Calibration. The certificate attests that the unit has been calibrated to its specifications by means of calibration equipment that is current and traceable to the National Institute of Standards and Technology (NIST). An annual recertification and maintenance service contract is also available for just under $100.

The instructions that come with the units are printed in a high-contrast color, on a laminated card with a self-adhesive back that can be permanently affixed to the top of the Check-Temp Calibrator. The simple, clear, and concise instructions are in both English and Spanish.

We noted only three minor problems with the Check-Temp:

1. There is a downside (although not a significant one) to the calibration port. The port is designed to accept all 5- and 8-inch, standard configuration, 1/8-inch-diameter probes, which are found on almost all dial thermometers, as well as most of the K-type electronic probes on digital thermometers. It will not, however, work with some proprietary electronic-thermometer probes such as those that come with the Atkins models.

2. The 140 and 160 models run silently. Both the 40 model and the Check-Temp II, however, have a small muffin fan mounted at the rear of the unit. The fan makes white noise slightly greater than that of a computer.

3. Finally, we did not find a UL[R] mark on either of the units we put through the paces. Although we noted no problems keeping our Check-Temps on 24-7, we nonetheless caution that the units should be turned off when not in use. After all, they do contain heating elements.

The accuracy and time savings realized with the Check-Temp units make them an essential addition to the tool kit of every health department, institutional kitchen, and food processor. They are also quite handy for HVAC engineers, who also rely on dial thermometers. For that application, each unit comes with a brush for periodic cleaning of the calibration port.

Prices start at just under $400 for the 140 and 160 models; the 40 model costs an additional $100. The Check-Temp II is $645, but we have always been steadfast in our opinion that two-point calibration is the only way to ensure accuracy, and the instrument is therefore well worth the additional cost.

(*.) Tel-Tru Manufacturing Company, P.O. Box 30144, Rochester, NY 14603-3144. Telephone: [phone]. E-mail: [less than][e-mail][greater than]. Web site: [less than]www.teltru.com[greater than].