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How to Verify Lab Stirring Temperatures

Establishing optimum temperatures to first develop then commercialize new products in the research lab should not be left to chance.  Because stirring is often involved in developing new products researchers depend on an accurate means of determining the optimum processing temperature. This post describes how to accurately verify lab stirring temperatures.

A Common Example of Temperature Verification

An example of temperature verification on the domestic scale is found in recommended cooking temperatures in the kitchen.

Fish, meat and poultry products are often packaged with instructions to cook, broil or roast until the internal temperature reaches X⁰F.

Oven temperatures can be set at this temperature and oven thermostats help control the oven temperature, but what is the internal temperature of the food?    Widely available temperature probes can be inserted in the food either from the beginning or periodically during the cooking to give a close approximation of the internal temperature.

“Close” may be OK (or maybe not OK) when you are roasting the holiday turkey but “close” does not apply when it comes to developing laboratory processes to be scaled up to commercial production.

Interestingly enough, however, is the fact that laboratory-developed and refined processes emulate those found in the kitchen.  The difference is the degree of accuracy and precision required and achieved.

Temperature Control and Verification for Hotplate Magnetic Stirrers

Hotplate magnetic stirrers such as the M and KM series available from CAT Scientific for flat and round-bottom  flasks enable lab personnel to control the speed of stirring accomplished by a magnetic stir bar (also called a “flea”) in the flask as well as the temperature of the process.

CAT hotplate magnet stirrers are capable of heating samples to temperatures above 400⁰C in 1⁰C increments and holding set temperature to within ±1⁰C operating from the control panel.  Operators see both the set and actual temperature. Our post on how magnetic stirrers work provides more detail.

But to continue our turkey-roasting analogy, temperatures displayed on the hotplate magnetic stirrer are those of the hotplate, not the sample.  Here temperature probes again come into play but in this case the probes are far more sophisticated than models used on the home front.

The CAT Pt100 Temperature Probe for Temperature Verification

The Pt100 temperature probe is the answer to accurate hotplate magnetic stirrer temperature measurement, verification and control.  This is used somewhat like the meat thermometer but is suspended in the sample rather than inserted in the roast.

(By way of explanation  Pt stands for platinum, a precious metal the properties of which enable accurate determination of the temperature.   In fact, they are more accurate than widely used thermocouples, which is why we offer them at CAT Scientific.)

But unlike the meat thermometer the Pt100 probe is equipped to take control of the magnetic stirrer itself.

Among its tasks are

  • monitoring the temperature
  • recording temperatures for record keeping
  • initiating shut-down procedures in the event of a magnetic stirrer malfunction or sample loss due to leakage or evaporation.

Moreover, when equipped with a probe the hotplate magnetic stirrer can control temperatures to ±0.04⁰C — a far tighter specification than ±1⁰C and, more significantly, it records sample temperature rather than the temperature of the hotplate.

This probe is attached by a clamp and support rod.  The tip is suspended at least 2 cm in the sample but not far enough to interfere with the rotating magnet.  Its wire is plugged into the back of the magnetic mixer making the probe the controller.

For more on this topic see our article on using Pt100 temperature probes or ask us a question on temperature control or other information on our line of scientific equipment.

Bob Wilcox

Bob Wilcox has represented CAT Scientific’s family of homogenizers, magnetic stirrers, liquid handling and related laboratory equipment since 2002 when Staufen, Germany-based CAT Ingenieurbüro M. Zipperer GMbH established operations in North America. Bob oversees CAT Scientific laboratory apparatus sales and service organization from the company’s headquarters in Paso Robles, CA. He also is in charge of the parent company’s line of JetCat jet turbines, turboprop, and helicopter power plants for hobbyists’ radio controlled fixed wing and helicopter model aircraft. -- Earlier in Bob’s career he was involved in visual and special effects as well as camera and electronics supervisory responsibilities for the motion picture and television industry.

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