CN101696948B - Capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field - Google Patents
Capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field Download PDFInfo
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- CN101696948B CN101696948B CN2009102104574A CN200910210457A CN101696948B CN 101696948 B CN101696948 B CN 101696948B CN 2009102104574 A CN2009102104574 A CN 2009102104574A CN 200910210457 A CN200910210457 A CN 200910210457A CN 101696948 B CN101696948 B CN 101696948B
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Abstract
The invention relates to a capillary melting point apparatus with heat-free hysteresis effect of a uniform temperature field, adopting a liquid heating medium for electric heating and comprising a heating system and a temperature measuring system. The heating system takes a quartz vacuum heat-insulated cup as a vessel, is provided with an upper electric heating wire and a lower electric heating wire and is heated by an intermediate medium of silicone oil; a detachable temperature-sensing element of the temperature measuring system is fixed between the upper electric heating wire and the lower electric heating wire, the tail end of the temperature-sensing element and a connecting lead are encapsulated in a stainless steel sleeve tube, and the main part of a Pt100 industrial platinum resistance thermometer of the temperature-sensing element is exposed out of the sleeve tube to directly contact with the medium; a platinum resistor is connected to a digital voltmeter through a lead at a four-wire system; and during measurement, the resistance of completely melt samples is recorded and a temperature value is obtained by the corresponding relationship of the resistance and the temperature. The temperature-sensing element can directly correct the temperature, is free from using melting point reference materials for correction and has convenient correction. The thermal hysteresis effect is corrected through theoretical calculation, thus the thermal hysteresis system error is eliminated in the full melting point measurement.
Description
Technical field
The present invention relates to a kind of fusing point instrument, relate in particular to a kind of uniform temperature field that has, the capillary melting point apparatus of no thermometer thermo-lag effect.
Background technology
The fusing point of material is meant the temperature when material is liquid state by solid state transformation.The fine melt point of material is meant material under certain heating rate, by solid-state temperature when changing liquid state into fully.The effect of fusing point is: one, qualitative identification organic compound.Because different organic compound fusing point differences, so fusing point can be used as the short-cut method of differentiating organic compound.Its two, measure organism purity.The organic fusing point that contains certain impurity is lower than pure organism, and the difference of its fusing point is directly proportional with the content of impurity, and therefore, fusing point can be used as the short-cut method of measuring organic compound.So fusing point is one of basic test content of industries such as medicine, chemical industry and food.
Fusing point can be measured by capillary melting point apparatus and hot desk-top fusing point instrument, also can measure by differential scanning calorimeter or differential thermal analyzer.Wherein, most widely used is capillary melting point apparatus.
Capillary melting point apparatus generally adopts industrial platinum resistance thermometer measure fine melt point at present.Because thermometer is fixedly mounted on the instrument, can not directly carry out temperature correction, must adopt the melting point of organic matter standard substance to carry out temperature correction, make calibration process loaded down with trivial details, accuracy of instrument be limited by standard substance (the standard substance uncertainty: 0.20 ℃, 1 ℃/min).Another problem of industrial platinum resistance thermometer is the thermo-lag effect, the systematic error certain to the measurement generation of fine melt point (about 0.07 ℃, 1 ℃/min).The only a few capillary melting point apparatus adopts the standard platinum resistance thermometer thermometric, and its thermometer thermo-lag effect is more remarkable, and systematic error reaches 0.50 ℃.In addition, capillary melting point apparatus is measured is the temperature of the temperature of certain limit around the temperature-sensitive platinum resistance, and the fine melt point that is encapsulated in the sample in the glass capillary is the temperature of a point, and therefore the homogeneity of temperature is measured influential to fusing point.For the fusing point instrument that adopts liquid heating medium, heating element is usually at container bottom, and the inhomogeneous temperature (about 0.40 ℃/centimetre) of the vertical direction that causes in the process of heat temperature raising causes 0.20 ℃ of fusing point test systematic error.
Therefore, demand developing a kind of uniform temperature field that has urgently, the capillary melting point apparatus of no thermometer thermo-lag effect is to solve the big problem of fusing point test systematic error that exists at present.
Summary of the invention
The objective of the invention is to: a kind of capillary melting point apparatus with no thermo-lag of uniform temperature field is provided, and making the fusing point instrument satisfy uncertainty of measurement is 0.2 ℃ requirement.
To achieve the above object of the invention, the technical solution used in the present invention is:
The present invention has the capillary melting point apparatus of the heat-free hysteresis effect of uniform temperature field, a kind of employing liquid heating medium, and Electric heating has uniform temperature field, and the capillary melting point apparatus of heat-free hysteresis effect comprises heating system and temp measuring system two parts.One, heating system: with quartzy vacuum insulation cup is container, has two parts electrical heating wire up and down, and heating voltage is provided by D.C. regulated power supply, and heating medium is a silicone oil.Its two, temp measuring system: with Pt100 industrial platinum resistance thermometer thermometric, temperature-sensing element is terminal and connect lead and be packaged in the stainless steel sleeve pipe, and the temperature-sensing element main part is exposed outer about 2.6 centimetres of sleeve pipe, directly contacts with silicone oil.Platinum resistance is connected to (precision: eight and half) on the high accuracy number voltage table by lead with four-wire system.The resistance of the platinum-resistance thermometer of record sample when all melting during measurement, the corresponding relation by resistance and temperature obtains temperature value.The thermo-lag effect is by the Theoretical Calculation correction.
The present invention compared with prior art has following remarkable advantages and beneficial effect:
The present invention has the capillary melting point apparatus of the heat-free hysteresis effect of uniform temperature field, owing to adopt the two sections heater strip to heat, vertical direction temperature field is 0.05 ℃/cm, vertical direction temperature field when being better than the heating of single hop heater strip (0.40 ℃/cm), the uncertainty of being introduced by warm field uniformity is 0.06 ℃, is better than 0.55 ℃ of the uncertainty of single hop heater strip heating.Because adopt dismountable industrial platinum resistance thermometer thermometric, temperature-sensing element can directly carry out temperature correction, avoid using the calibration of fusing point standard substance, calibration is convenient.Since by the Theoretical Calculation correction thermo-lag effect, make the fine melt point measurement eliminated the thermo-lag systematic error (0.07 ℃, heating rate: 1 ℃/min).More than comprehensive, the present invention measures organism fine melt point measurement uncertainty and reaches 0.2 ℃ of (heating rate: 1 ℃/min).
Description of drawings
Fig. 1 is an apparatus structure synoptic diagram of the present invention;
Fig. 2 is the present invention's temperature field uniformity synoptic diagram.
Embodiment
Below in conjunction with accompanying drawing specific embodiments of the invention are illustrated:
A kind of capillary melting point apparatus with uniform temperature field, heat-free hysteresis effect as shown in Figure 1, it comprises heating systems and two parts of thermometric system.
Heating systems comprises top heater strip 1 and the lower heating silk 2 that is used to heat, and the D.C. regulated power supply 7 that electric current is provided to heater strip; Be used for vacuum insulation cup 4, be used for methyl-silicone oil 9, and be used for stirring and make the uniform stirrer 6 of system temperature as heating medium as the quartz system of heating systems container.
The thermometric system comprises the Pt100 industrial platinum resistance thermometer 3 that is used for thermometric, and the high accuracy number voltage table 8 that is used to measure the resistance of platinum-resistance thermometer.The glass capillary 5 that is used for packaged sample closes on thermometer and places, and is in the temperature-sensing element medium position on the vertical direction.
See also shown in Figure 2ly, be the inner warm field uniformity synoptic diagram of fusing point instrument heating systems in the measuring process.Comprise vacuum insulation cup 4, top heater strip 1 and lower heating silk 2, and Pt100 platinum-resistance thermometer 3.A, what B, C represented is 3 location points adjacent with the position, upper, middle and lower of Pt100 platinum-resistance thermometer temperature-sensing element.
The fusing point instrument must be delivered to metrological service and be carried out temperature correction with Pt100 industrial platinum resistance thermometer together with the high accuracy number voltage table before use.The mode of multiple spot calibration is adopted in calibration, and promptly at 30 ℃, 60 ℃, 90 ℃, 100 ℃, 120 ℃, 150 ℃, 180 ℃, 9 temperature spots such as 210 ℃ and 240 ℃ are calibrated, and provide the resistance value under each temperature spot; Temperature is read by standard thermometer, and resistance value is read by digital voltmeter.The corresponding relation of temperature and resistance value through over-fitting, obtains a quadratic equation with one unknown; During actual thermometric,, obtain temperature value according to this Equation for Calculating by the resistance value that records.Thermometer thermometric standard uncertainty is 0.03 ℃.
When measuring melting point of organic matter, sample is packaged in the kapillary (capillary diameter 1.00mm ± 0.02mm, height of specimen 3.0mm ± 0.3mm).Pt100 industrial platinum resistance thermometer is fixed on up and down in the middle of two heater strips.Thermometer is connected on the high accuracy number voltage table by four-wire system; Digital voltmeter is adjusted to four-wire system resistance measurement pattern.Two parts heater strip adopts the heating voltage of identical size up and down, the regulation voltage level size, and the system heating rate of making reaches the appointment requirement, as 1 ℃/min.As shown in Figure 2, under two parts heater strip heating condition, when system temperature was about 120 ℃, the temperature that A point, B point and C are ordered in the synchronization was respectively 119.90 ℃, 120.00 ℃ and 119.89 ℃ up and down, and vertical direction temperature field is less than 0.05 ℃/cm; And only adopt under the heating condition of lower heating silk, during the same terms, the temperature that A point, B point and C are ordered is respectively 119.67 ℃, 120.00 ℃ and 120.70 ℃, and vertical direction temperature field is about 0.40 ℃/cm.Promptly adopt the method for two parts heating up and down, obviously improved warm field uniformity, the temperature standard uncertainty that warm field uniformity is introduced is 0.06 ℃, much smaller than 0.55 ℃ of single hop heater strip.
Under constant heating rate, heat, the sample in the kapillary is melted fully; Reach when melting fully, promptly during fine melt point, the resistance value that the record digital voltmeter is measured.By above-mentioned fit equation, obtain the fusing point measured value.Consider the thermo-lag effect of platinum-resistance thermometer, need to adopt following formula that temperature value is revised.
In the following formula, T measures temperature, and T ' is an actual temperature, τ
0Be the time constant of platinum-resistance thermometer, dT/dt is a heating rate.Timeconstant
0Can obtain representative value about 4 seconds by actual measurement.Through the temperature value of thermo-lag correction, be the capillary melting point value of sample.
With the melting point of organic matter that above-mentioned fusing point instrument is measured, its combined standard uncertainty is 0.10 ℃, and expanded uncertainty is 0.20 ℃.
It should be noted that at last: above embodiment only in order to the explanation the present invention and and unrestricted technical scheme described in the invention; Therefore, although this instructions has been described in detail the present invention with reference to each above-mentioned embodiment,, those of ordinary skill in the art should be appreciated that still and can make amendment or be equal to replacement the present invention; And all do not break away from the technical scheme and the improvement thereof of the spirit and scope of invention, and it all should be encompassed in the middle of the claim scope of the present invention.
Claims (5)
1. the capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field adopts liquid heating medium, and electrical heating comprises heating system and temp measuring system two parts; It is characterized in that: described heating system is a container with quartzy vacuum insulation cup, has two parts electrical heating wire up and down, heats by liquid heating medium;
Described temp measuring system, dismountable platinum-resistance thermometer temperature-sensing element are fixed on up and down in the middle of two heater strips, and it is terminal and connect lead and be packaged in the stainless steel sleeve pipe, and the temperature-sensing element main part is exposed outside the sleeve pipe, directly contacts with medium; Platinum-resistance thermometer is connected to measuring apparatus by lead with four-wire system; The resistance of the platinum-resistance thermometer of record sample when all melting during measurement, the corresponding relation by resistance and temperature obtains temperature value.
2. the capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field according to claim 1 is characterized in that: described temperature-sensing element is a Pt100 industrial platinum resistance thermometer.
3. the capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field according to claim 1 is characterized in that: the heating voltage of described electrical heating wire is a D.C. regulated power supply.
4. the capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field according to claim 1 is characterized in that: described measuring apparatus is a digital voltmeter.
5. the capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field according to claim 1 is characterized in that: described heating medium is a silicone oil.
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| CN2009102104574A CN101696948B (en) | 2009-11-03 | 2009-11-03 | Capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field |
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| CN2009102104574A CN101696948B (en) | 2009-11-03 | 2009-11-03 | Capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field |
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| CN108387600A (en) * | 2018-01-23 | 2018-08-10 | 上海佳航仪器仪表有限公司 | A kind of full-automatic grease fusing point test device |
| CN111122642B (en) * | 2019-12-12 | 2024-02-13 | 王巍群 | Digital automatic melting point instrument based on ultrasonic imaging principle |
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