laboratory thermometer limitations

0000004523 00000 n Hysteresis (where the measured value depends on the direction from which it was approached) can be seen in simple bimetallic (dial) thermometers. Disadvantages and Advantages of a Digital Thermometer, BBC News Health: Ear Thermometers 'Unreliable'. Certifying organizations such as JCAHO (Joint Commission) require laboratory instrumentation to be NIST certified. The stability of reagents kept at “room temperature” decreases if the temperature exceeds about 35^0C. measure temperature variations over a distance of less than 1 cm, material 0000008155 00000 n Etekcity Infrared Thermometer 774 (Not for Human) Temperature Gun Non-Contact Digital Laser Thermometer-58℉ to 716℉ (-50 to 380℃), Standard Size, Black by Etekcity $27.99 $ 27 . Krista Raye is a Steel Magnolia who began writing professionally in 2009 with eHow, Answerbag and Trails. Thermco B200CWSSC General Laboratory Blue Spirit Filled Thermometer, Coated, -10 to 200°C Range, 1°C Division, Total Immersion, 406mm Length 3.8 out of 5 stars 19 $26.38 $ 26 . of emitting surface needs to be known, affected The time for a sensor to reach 99% of measured value is referred to as the “t99” time. The disadvantages are that they break easily and there is risk of mercury poisoning if the glass tube breaks. Another advantage is the easy-to-read digital display. Thermocouples are an accepted lower-cost solution to temperature measurement in industry and can be found in many laboratory instruments. All this depends on the design and performance of the HVAC system servicing the clinical laboratory. At first glance, a digital thermometer seems to be the best choice for measuring temperatures. This all highlights the need for measurements being taken at a constant temperature and why many clinical laboratories operate at room temperature. Some sensors respond in less than a second, some take minutes. Even calibrated thermometers will eventually have errors due to offset, scale and linearity errors. being heated. Laser thermometers advantages. These may include the following: Temperature measurement accuracy is established through calibration. It is sometimes challenging. frequent calibration to maintain accuracy, can All rights reserved. However, before you can develop confidence in their ability to give fast temperatures, you must understand their limitations. Ensure that your NIST calibration of the device includes calibration of the total sensor-read-out system, as temperature effects on the readout device can be a subtle source of error as well. Glass thermometers are an accurate way to ensure environmental temperature is as it should be, which may be essential when handling temperature sensitive materials. the tape prevents the stretching of that side of the foil, so the 'bimaterial' Various types of temperature sensors less hazardous. computer network. Since water is commonly used as a reference, it also has a different viscosity at different temperatures. 0000001593 00000 n You can see this on the calibration certificate in the “as found” (incoming) and “as left” (outgoing) documentation of performance. This column addresses compliance, regulatory, legal, certification, and additional concerns in the lab. xڬSohg~޻�rI�k���ؔ�,j6Ƹ6�E�tQ����V�X)c��}���E�H�jZ;�eC��Z� ������3�HK��싛��:�M��D�w �~ߏ{߇�y���}���� �&���/�&�%�!������f��������;�O|#��D�����V&�x*_�v�w6��ǽ�M�k�r�ް��4�o�N��� o��d//{�G�ܜ�O��s-gL��.-��юt�")�_�Z��iH~y�{a��|��������L��3�Zz���ޱ�&��X�nZ��CIO�p��%^S���. You need to know precisely what the temperature is, even when the lab is unoccupied. Some of the measurement difficulties have to do with thermal gradients in the material being measured, especially with materials that have poor thermal conductivity, such as plastics. Copyright 2020 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. This includes instruments, incubators, refrigerators-freezers, and specimen holding rooms. It’s the basic building block of most analytical measurements. Alcohol thermometer (compared to a mercury thermometer) lower freezing point (-114 ºC) less durable (alcohol evaporates) larger coefficient of expansion. Note: With accuracy limitations typically >1C, most healthcare (regulated, audited and accredited) The “dependable” feature in automated temperature monitoring systems comes from their alarming and documentation capabilities. Let’s not forget that it’s people who both record laboratory temperature data and are responsible for that data. 99 Another advantage is the easy-to-read digital display. The table below compares the various Here, a different approach for temperature mapping, sensor selection and placement needs to be taken as compared to the macro environment. Wide range of –58 to 302°F/–50 to 150°C covers 90 percent of lab temperature measurements. NIST traceability does not necessarily mean “accurate,” so make sure there is proof in any claims of “NIST-certified” equipment. This article gives a quick overview of both the importance of accurate temperature measurement in the clinical laboratory and some common misconceptions about the instrumentation that is used and what can be done to help maintain temperature control. Approved Standard 1990, CLSI Document 12-A2. To achieve this temperature range with equivalent precision … if you point an IR gun at a window, you'll be measuring the temperature of the window pane, not the outside temp). All rights reserved. However, in general, NIST does not require or recommend any set recalibration interval for measuring standards or instrumentation. are listed in Section 3.1. But what is “room temperature”? In general, the “macro” environment deals with the laboratory work area itself. Infrared thermometers: Only measure surface temperatures and NOT the internal temperature of food or other materials; Require adjustments depending on the surface being measured (See Adjust for Emissivity) So the laboratory environment, analytical reactions, instrumentation and materials must be monitored and controlled to required temperatures. It does not actually mean the laboratory instrument was “adjusted” to meet design specifications. Glass thermometers are considered to be a quick and effective way of measuring temperature changes, which may vital to an experimental process. However, like all thermometers, liquid-in-glass thermometers are subject to drift as a function of time and maximum temperature of use. The challenge is not to just do it, but to do it right: choosing the right components, knowing their advantages and limitations, ensuring their accuracy to meet regulatory requirements, and maintaining required records. It is not always difficult. For example, at cryogenic temperatures (-200^0 C), accuracies of +/-5^0 C can be done with care, but +/-0.1^0 C can be difficult. The foil expands when it is heated, but What you are actually measuring is the temperature of the sensor. situations. 0000003245 00000 n For instance, mercury thermometers are the standard equipment at Clinical and Laboratory Standards Institute. Automated vs. manual temperature monitoring. Because of this they are often called negative temperature coefficient (NTC) sensors. * In some cases, Infrared Thermometers can be MORE accurate than a surface probe because surface probes have their own temperature and can affect the surface being measured by coming into contact with it. A typical accuracy for a platinum resistance thermometer is +/-0.5^0C, with some designs exceeding +/-0.07^0C. The entire measuring “system” (sensor and read-out device) should be traceable back to a known standard. When I measure, I’m measuring the temperature of the sample. Also, any of these temperature sensors can drift over time and due to temperature cycling. Compared with resistance-type thermometers, thermocouples offer the advantage of a higher upper temperature limit, up to several thousand degrees Celsius.