SI21628A - Bath for simultaneous calibration of medical contactless and contact thermometers - Google Patents

Abstract

The highly stable and homogeneous bath for simultaneous calibration of medical contactless and contact thermometers for the application in metrology, medicine, veterinary science and other medical purposes provides a special application of throughput or circulation of liquid from the auxiliary tube (1), which features heaters (3), a cooling spiral (4) and a mixer (5), into two main tubes (2), by which it returns back to the auxiliary tube (1). In the main tube (2) there are a black body (6) and one or more stabilising cylinders (7), which are located together or individually, where the central axes of the main tubes regarding the central axis of the auxiliary tube form an angle between 180 and 60 degrees. A thermometer holder (9) can be used instead of the stabilising cylinder (7), when the bath error during calibration is satisfactory. The black body (6) serves for the calibration of contact thermometers and is coloured with a colour, which features a highly emissive property and is located in the main tube (2) either horizontally or vertically. The shapes of the black bodies are recommended by standards. The stabilising cylinder (7) serves for the calibration of contactless thermometers and considerably improves the temperature stability and homogeneousness of the bath. The true temperature is determined by the integrated or external reference thermometer (8), which can be traced back to the national etalon. The black body (6) and stabilising cylinder (7) are made from metal with a good thermal conductivity. The dimensions of individual elements as well as the bath itself can be adapted to current requirements or needs.

Description

University of Ljubljana

Faculty of Electrical Engineering

Metrology and Quality Laboratory

Igor Pušnik, Jovan Bojkovski and Janko Drnovšek

Tržaška 25

1000 Ljubljana

BATH for simultaneous calibration of medical non-contact and contact thermometers

The subject of the invention is a highly stable and homogeneous bath for simultaneous calibration of contactless and contact thermometers for medical use and protection of health in a broad sense. The field of technology covered by the bath is metrology, since it is basically intended for the calibration or calibration of contactless (radiation, infrared, pyrometers) thermometers and the calibration of contact thermometers (liquid thermometers, thermometers with digital temperature displays, thermistors, resistive thermometers, thermocouples) comparison with a reference thermometer traceable to a national or international standard.

According to available data, no bath has been developed so far to allow simultaneous calibration of contactless and contact thermometers. The most similar solution to the present invention is the patent of Isothermal Technology Ltd. from the United Kingdom under GB2361536. The solution in this patent does not allow for the simultaneous calibration of contactless and contact thermometers.

Many contactless and contact thermometers are used in medicine, which need to be calibrated or their accuracy checked. The calibration ensures metrological traceability to the basic units of the international SI unit system. The request follows directly from the European directive concerning medical devices (Council Directive 93/42 / EEC of 14 June 1993 conceming medical devices, Medical Device Directive) and requires the conformity of the actual characteristics of medical devices with the specifications given by manufacturers. The developed bath thus follows the European technical regulations and enables the conformity of the medical contactless and contact thermometers with the manufacturers specifications to be checked. Contactless and contact thermometers are also useful for veterinary and other medical purposes. An appropriate system is required to calibrate or control both types of thermometers. The disadvantage of the baths developed so far was the ability to calibrate only contact or non-contact thermometers, and impaired temperature stability and homogeneity. We do not know that a black body bath would be developed for calibrating medical radiation thermometers. The closest patented solution is a calibrator for the calibration of a Shenvood medical ear thermometer (patent number US6179785), which does not meet the requirements of the standards below (EN 12470-5: 2003, ASTM Designation E 1965-98, JIS). The problem with this calibrator is the lower emissivity and poorer temperature stability and homogeneity.

The developed bath has a special design of flowing liquid from overflow, from the auxiliary tube 1, which houses the heaters 3, the cooling coil 4 and the mixer 5, into one or two main pipes 2. The black body 6 and the stabilization cylinder 7, which are if necessary, and depending on the space available, more may be provided together in the main tube 2 (sketch 1, sketch 2), or in one main tube 2 a black body 6 may be installed and in the other main tube 2 a stabilization cylinder 7 (sketch) 3, sketch 4). The stabilizer cylinder 7 can also be replaced by a contact thermometer holder 9 (Figure 9). The center axes of the main pipes 2 may have an angle of 180 ° (Figure 3) to 60 ° (Figure 4) with respect to the center axis of the auxiliary pipes 1. Calibration traceability is ensured by one or more built-in reference thermometers 8 or external reference thermometers traceable to a national or international standard.

The black body 6 is used for calibration of contactless thermometers. Black body shapes are recommended in the standards:

- European standard EN 12470-5: 2003 Clinical thermometers - Part 5: Performance of infrared ear thermometers (with maximum device), CEN, Brussels (sketch 5) American standard ASTM, Designation E 1965 - 98: Standard Specification for Infrared Thermometers for Intermittent Patient Temperature Determination, ASTM Standards Annual Book 1998, West Conshohocken, PA 19428, USA (sketch 6)

- Japanese Industrial Standard JIS (Infrared ear thermometers - draft standard, Japan, 2002). sketch 7)

The black body 6 is made of metal with good thermal conductivity, usually copper. The interior of the black body is painted with a special color that is temperature resistant and has high emissivity (typically around 0.9). Prior to painting, the surface inside the black body must be greasy and sandblasted to increase the light scattering at reflection and consequently to increase the emissivity. The application of the paint is approximately 0.1 mm in three layers, with at least the last drying being carried out at elevated temperature (e.g. 100 ° C) for at least 24 hours. The black body is mounted in a side tube either horizontally (sketch 7) or vertically sketch 2j with respect to the body axis.

Stabilization cylinder 7 (Figure 8) serves to calibrate contact thermometers and significantly improve the temperature stability and homogeneity of the bath. It is made of metal with good thermal conductivity (copper, aluminum) and galvanized to prevent oxidation.

Instead of stabilizing cylinder 7, a thermometer holder 9 {9j can be used to allow a plurality of thermometers to be mounted in the bath. It is made of stainless steel.

The description of the invention is given in the form of three basic variants (variant 1 - sketch 1, variant 2 - sketch 3, variant 3 - sketch 4), with each of the variants having the possibility of vertical or horizontal positioning of the black body. An example is shown in Figure 1 and Figure 2 for variant 1. The variants of black bodies for bathing in variants 1, 2, or 3 are shown in Figures 5, 6 and 7.

Bath variants

Figure 1: Bath variant IA

In variant IA, we have an auxiliary tube 1, which houses heaters 3, a cooling coil 4, and a mixer 5, and one main tube 2, which houses a black body 6 and a stabilizer cylinder 7. The true temperature value is determined by the reference thermometer 8. The layout of the black body 6 is horizontal with respect to the body axis.

Figure 2: Bath variant IB

The difference with the IA variant is only the layout of the black body 6, which is vertical with respect to the body axis.

Figure 3: Variant 2 bath

In variant 2 we have an auxiliary tube 1 with heaters 3, a cooling coil 4 and a mixer 5, and two main pipes 2. In one main pipe there is a black body 6 and in the other main pipe 2 there is a stabilizing cylinder 7. The true temperature value is determined by the reference thermometer 8. The center axes of the main tubes with respect to the median axis of the auxiliary tubes range as 180 °.

Figure 4: Variant 3 bath

In variant 3 we have an auxiliary tube 1 with heaters 3, a cooling coil 4 and a mixer 5, and two main pipes 2. In one main pipe 2 there is a black body 6 and in the other main pipe there is a stabilization cylinder 7. The true value of the temperature is determined by the reference thermometer 8. The center axes of the main tubes with respect to the median axis of the auxiliary tubes range as 60 °.

Black body variants for installation in baths in variants 1,2, and 3.

According to the three basic international standards for medical radiation thermometers, the following versions of three black bodies are described below. Each of the three black bodies can be installed in one of the baths in variants 1, 2 or 3.

Figure 5: Black body according to EN 12470-5: 2003

The black body 6 according to the European standard EN 12470-5: 2003 is a 30 ° cut-off cylinder. The walls of the cylinder should be as thin as possible to allow heat to be transferred from the liquid to the surface inside the black body faster. The black body flange is well insulated from its metal part and is made of a material with a low coefficient of thermal conductivity.

Figure 6: ASTM black body, Designation E 1965 - 98

The black body 6 according to the American ASTM standard, Designation E 1965 - 98, is a cone at an angle of approximately 36 °. The walls of the cylinder should be as thin as possible to allow heat to be transferred from the liquid to the surface inside the black body faster. The black body flange is well insulated from its metal part and is made of a material with a low coefficient of thermal conductivity.

Figure 7: Black body according to Japanese Industrial Standard JIS proposal Black body 6 according to Japanese JIS proposal is a narrowing cylinder at the opening. At the entrance, the angle between the axis of the cylinder and the wall extends about 50 °, and at the bottom, about 120 °. The walls of the cylinder should be as thin as possible to allow the heat to be transferred from the liquid to the surface inside the black body faster. The black body flange is well insulated from its metal part and is made of a material with a low coefficient of thermal conductivity.

Additional elements for calibration of contact thermometers

Figure 8: Stabilizer cylinder

The stabilizer cylinder 7 has different number of holes of different diameters. The number depends on the diameter of the stabilizer cylinder and the desired bore diameters for the contact thermometers. These must match the diameters of the thermometers that are inserted into the bores during calibration. It is used to improve the temperature stability and homogeneity of the bath and thereby reduce the calibration uncertainty.

Figure 9: Thermometer holder

The thermometer holder 9 has a large number of holes of different diameters and serves to place a large number of contact thermometers 8 in the bath. The number of holes depends on the desired bore diameters for the contact thermometers. It is used instead of stabilizer roller 7 when the bath uncertainty in calibration is satisfactory.

Method of Use of the Invention

The bath will be used to ensure the traceability of medical contactless and contact thermometers in the range of 20 ° C to 90 ° C. Traceability will be ensured by calibration using a built-in or external reference thermometer 8 that is traceable to a national or international standard. The reference thermometer 8 determines the true value of the bath temperature, which determines the accuracy of the calibrated thermometers. When determining the uncertainty of calibrated thermometers, it is also necessary to take into account the metrological parameters of the bath, which are determined by regular periodic calibration of the bath. It is intended for use in hospitals, major health centers and other health care institutions, as well as calibration laboratories. In addition to medical thermometers, the bath can be used to calibrate all contactless and contact thermometers in the specified temperature range. The dimensions of the individual elements of the invention can be adapted to the current requirements or needs.

Claims (4)

PATENT APPLICATIONS 1. A highly stable and homogeneous bath for simultaneous calibration of contactless and contact thermometers for use in metrology, medicine, veterinary medicine and other medical purposes, characterized in that the auxiliary tube (1) in which the heaters (3) are located, a cooling coil (4) and a mixer (5) and one main pipe (2) in which the black body (6) or the black body (6) or the horizontal body is positioned simultaneously, either horizontally or vertically. black body variants prescribed by international standards and depending on the diameter one or more stabilization cylinders (7) or. instead, a thermometer holder (9), the true temperature value being determined by a built-in or external reference thermometer (8). 2. Highly stable and homogeneous bath for simultaneous calibration of contactless and contact thermometers for use in metrology, medicine, veterinary medicine and other medical purposes, characterized in that the auxiliary tube (1) with heaters (3), a cooling coil (3) are located in the bath housing. 4) and a mixer and two main tubes (2), the center axes of which are relative to the center axis of the auxiliary tubes by an angle of 180 ° and in which a black body is placed horizontally or vertically with respect to the body axis of the auxiliary tube ( 6) or. black body variants prescribed by international standards, and in the second main pipe a stabilizer cylinder (7) or. a thermometer holder (9), while the true temperature value is determined by a built-in or external reference thermometer (8). 3. Highly stable and homogeneous bath for simultaneous calibration of contactless and contact thermometers for use in metrology, medicine, veterinary medicine and other medical purposes, characterized in that the auxiliary tube (1) with heaters (3), a cooling coil (3) are located in the bath housing. 4) and the mixer (5) and the two main pipes (2), the center axes of which are relative to the center axis of the auxiliary tubes, with an angle of 60 ° and in which, independently of one main pipe (2), they are placed either horizontally or vertically with respect to body axis mounted black body (6) or. black body variants prescribed by international standards, and in the second main pipe (2) a stabilizer cylinder (7) or. a thermometer holder (9), while the true temperature value is determined by a built-in or external reference thermometer (8). 4. The process of simultaneous calibration of contactless or contact thermometers in a highly stable and homogeneous bath for use in metrology, medicine, veterinary medicine and for other medical purposes, characterized in that it is characterized by flow or flow. of circulating fluid from the auxiliary tube (1) in which the heaters (3), the cooling coil (4) and the mixer (5) are placed, into one or two main pipes (2), in which they are combined (one main pipe) or in individually (several main tubes) there are arbitrarily horizontal or vertically positioned black bodies (6) or. versions of black bodies according to international standards and one or more stabilization cylinders (7) or. a thermometer holder (9), where fluid from the main tubes is poured back into the auxiliary tube, while the true temperature is determined by a built-in or external reference thermometer (8), thereby achieving high stability that can be increased by using one or more stabilization cylinders and homogeneity of bath temperature, thereby simultaneously calibrating contactless and contact thermometers.