JJG 701-2008 Melting Point Tester Verification Procedure JJG701-2008 Standard Download Decompression Password: www.bzxz.net
This procedure applies to the initial verification, subsequent verification and in-use inspection of melting point testers. Melting point testers include capillary melting point testers and hot stage melting point testers.


1 Scope (1)
2 Terminology (1)
3 Overview (1)
4 Metrological performance requirements (1)
4.1 Indication error (1)
4.2 Indication repeatability (1)
4.3 Linear heating rate error (2)
5 General technical requirements (2)
5.1 Appearance (2)
5.2 Insulation resistance (2)
6 Measuring instrument control (2)
6.1 Verification conditions (2)
6.2 Verification items (3) 6.3
Verification method (3)
6.4 Processing of verification results (5)
6.5 Calibration cycle (6)
Appendix A Melting point standard substances and instructions for use (7)
Appendix B Calibration certificate (inner page) format (9)
Appendix C Calibration result notice (inner page) format (10)
Appendix D Indication correction of glass liquid thermometer (11)
Appendix E Melting point tester calibration record format (12)

National Metrology Verification Regulations of the People's Republic of China JJG701—2008
Melting-point Measurement Instruments2008 - 12 22 Issued
Implementation on 200906—22 Issued by the General Administration of Quality Supervision, Inspection and Quarantine JJG701—208
Verification Rcgulation of
Melting-point Measurement InstruncntsJJG 701
Daige JJG7011990
JJG463
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine on December 22, 2008, and came into effect on June 221, 2009.
Responsible unit: National Technical Committee for Physical and Chemical Metrology, main drafting unit: Dajin Metrology Supervision and Inspection Science Research Institute Participating drafting unit: Haijing Precision Scientific Instrument Co., Ltd. Tianjin Renda Renfa Technology Co., Ltd.
This regulation entrusts the National Technical Committee for Physical and Chemical Metrology to be responsible for the interpretation of this regulation. The main drafter of this regulation:
JJG 701-2108
Zhang Dajian (Tianjin Metrology Supervision and Inspection Science Research Institute) Wei Shulong (Tianjin Metrology Supervision and Inspection Science Research Institute) Participating drafters:
Zhu Jizhong (Shihai Precision Scientific Instrument Co., Ltd.) Li Ciyang (Tianjin Tianren Tianfa Technology Co., Ltd.) Song Wei (Tianjin University)
Scope·
Terms·
Overview·bzxz.net
1 Metrology performance requirements
4. Indication error
4.2 Indication repeatability
Linear heating rate error-
5 Technical requirements
5.． ． Appearance…．
5. 2 Insulation resistance
Control of measuring instruments
Verification conditions
Verification items
Verification methods
Processing of verification results
Verification period:
Melting point standard substances and instructions for use
Gradually addendum A
Appendix B
Appendix C
Appendix D
Appendix E
Verification certificate (inside page) format
JJG 701—2008
Verification Result Notice (Inner Page) Format
Correction of Indication of Glass Liquid Thermometer
Verification Record Format of Melting Point Tester
(2)
(3)
(3)
(5)
1 Scope
JJG701—2008
Verification Procedure for Melting Point Tester
This procedure applies to the initial verification, subsequent verification and in-use inspection of melting point testers (hereinafter referred to as instruments). Melting point testers include capillary melting point testers and hot stage melting point testers. 2 Terminology
2. Capillary Melting Point
The melting point measured by the capillary method is called the capillary melting point. Its measurement belongs to indirect measurement. The temperature it measures is the ambient temperature of the capillary sample: not the temperature of the sample. 2.2 Thermodynamic Melting Point
When a crystalline substance is heated in dry air at a certain pressure, the temperature at which a small amount of solid and liquid phases are in thermodynamic equilibrium is called the thermodynamic melting point. 3 Overview
The capillary melting point tester is used to measure the capillary melting point or thermodynamic melting point of crystalline chemicals and medicines. The measuring principle of the instrument is to heat the sample in the capillary in a temperature transfer medium, observe its phase change process or the change in transmittance during the phase change to determine the melting point. It mainly consists of heating, temperature control, temperature measurement and other parts. The temperature transfer medium can be liquid or solid.
Thermodynamic melting point is the theoretical melting point of a crystalline substance under ideal conditions. It is generally obtained by mathematically calculating the freezing point and melting point after measuring them. Some capillary melting point instruments also have the function of measuring thermodynamic melting point. They are obtained by measuring the capillary melting point of the sample and calculating it after calibrating the thermodynamic melting point determination function of the instrument with melting point standard materials. The hot stage melting point tester is used to measure the melting point of crystalline chemicals, medicines and some polymers. The measuring principle of the instrument is to heat the sample between the slide and the cover glass on the hot stage, observe its phase change process through a microscope with a polarizing device or automatically measure the change in light transmission performance during the phase change to determine the melting point. It mainly consists of a hot stage, temperature measurement, temperature control and a microscope with a polarizing device or photoelectric detection. 4 Metrological performance requirements
The capillary melting point tester is divided into four levels of accuracy according to the maximum allowable error within the measurement range of less than or equal to 200℃, which are 0.2, 0.5, 1.0, and 1.5; the hot stage melting point tester can have different accuracy levels in different measurement ranges, which are 0.5, 1.0, and 1.5. 4.1 Indication error
The instrument indication error verification result should not exceed the provisions of the metrological performance requirements (Table 1). 4.2 Repeatability of indication
The verification result of the repeatability of the indication of the instrument shall not exceed the requirements of the metrological performance requirements (Table 1). 1.3 Error of linear heating rate
I.IG701—200X
The verification result of the error of linear heating rate of the instrument shall not exceed the requirements of the metrological performance requirements (Table 1). Table 1 Metering performance requirements
Accuracy grade and measurement range
Test items
Error of indication/
Repeatability of indication/C:
False shutdown of linear heating rate
5 General technical requirements
5.1. Appearance
Oil-to-water melting point tester
2002092010
200200
2002 200
- 0. 1+ 0. 5
Hot-stage melting point tester
5.1.1 The instrument shall have the following labels: instrument name, model, manufacturer name, factory time and instrument number, 0.5
5.1.2 The function keys on the instrument panel shall operate normally, and the labels shall be clear and complete. The display of the digital display instrument shall be clear and complete. For instruments using glass liquid thermometers, the thermometers shall be intact and attached with valid verification and calibration certificates. 5.1.3 The heating element of the heating part of the instrument shall be intact. For instruments using liquid as the temperature transfer medium, the temperature transfer medium shall be clear and uniform, without thin condensation, sedimentation or filaments. 5.2 Insulation resistance
When the instrument is not in operation, the insulation resistance between the phase line of the power plug and the exposed metal part of the instrument casing should be no less than 20M when the test voltage is 500V. 2.6 Measuring instrument control
Measuring instrument control includes: initial calibration, continuous calibration and in-use inspection. 6. Calibration conditions
6.1.1 Environmental conditions
6.1.1.1 Ambient temperature 20 (5) °C, and the temperature fluctuation during calibration is no more than +2 °C: 6.1.1.2 Humidity is no more than 85% RH: 6.1.1.3 Power supply voltage (220=22) V, frequency (50+1) Hz; 6.1.1.4 The laboratory should be free of electromagnetic interference. 6. .2 Calibration equipment
Stopwatch or other timer: resolution 0.01s;6.1.2.1
6.1.2.2 Standard platinum resistance thermometer: Standard resistance thermometer, digital temperature measuring instrument: resolution 0.01℃, this instrument is used in conjunction with the second-class standard platinum resistance thermometer6. 1. 2. 3
IG 701—2008
6.1.2. AC voltmeter: 150/500V, accuracy 1.0 grade;6.1.2.5 Megaohmmeter: test voltage 500V
The above equipment should be used with a valid calibration certificate. 6.1.3 Standard substances
6.1.3.1 The melting point standard substances used for instrument calibration must be certified melting point standard substances approved and issued by the national metrology administration. For instruments of level 0.2 and 0.5, first-class melting point standard materials shall be used. For instruments of other levels, first-class melting point standard materials can be used: 6.1.3.2 When the temperature transfer medium of the capillary melting point tester is liquid, use the capillary melting point standard materials with type A correction tube package. When the temperature transfer medium is solid, see Appendix A for specifications. 6.2 Verification Items Verification Items See Table 6 Verification Item H Appearance Inspection Value Error Minimum Value Relative Strength Linear Heating Rate Error Insulation Resistance Note: “+” indicates the first inspection item, “-” indicates the inspection item. 6.3 Inspection Appearance inspection Carry out according to the requirements of 5.1 6.3.2 Indication error After the instrument is stable, do not check and continue to check. Take appropriate melting point standard mass points and measure each melting point three times: the difference between the average value and the standard value is the indication. 6.3.2.1 Capillary melting point determination instrument Preparation of capillary sample: grind the melting point standard substance in a vacuum sieve and dry it. Take a dry and clean glass tube about 800mm long and place it on a vacuum sieve. Place the capillary tube containing the melting point standard substance from the top and let it fall from the middle: repeat the step to make the powder of the standard substance gather tightly at the bottom of the tube, and its height should be 3mm; b) Set the initial temperature of the instrument at 3℃ (humidification rate is 0.2℃/min) or 15℃ (heating rate is 1.0C/min) lower than the melting point value. When the temperature transfer medium reaches the stable set temperature, place the capillary tube at a suitable position in the temperature transfer medium and perform temperature calibration at the set temperature rate; c) For the instrument using platinum resistance thermometer to measure temperature, three melting point standard substances are used for verification, and one is selected from each of the thirteen temperature ranges of (50~100)℃, (100200)℃, 200℃ and so on: For the instrument using glass liquid thermometer to measure temperature, according to the different temperature measurement ranges of the thermometer, each thermometer generally needs to be verified with two melting point standard substances: 701—2008
d) Criteria for visual judgment of capillary melting point (full melting point): The temperature at which the sample in the capillary is completely liquefied (clarified) is called the full melting point or full melting point. The instrument for measuring melting point is tested according to the full melting (final melting) temperature indication of the instrument;
c) The instrument is heated at a heating rate of 0.2℃/min or 1.5℃/min. According to the requirements of c), a melting point standard substance is selected and its capillary melting point (full melting point) is measured: the measurement is repeated once, and the difference between the average value of the measurement and the standard value of the capillary melting point (full melting point) of the standard substance with the same rate is the indication error of the instrument. The indication error of the instrument is calculated according to formula (1):
AT T: -T
Where: [- indication error;
The average value of the melting point measurement values;
TThe standard value of the melting point standard substance.
) For instruments that use glass liquid thermometers to measure temperature, the indication should be corrected according to the different immersion methods of the thermometer. The correction method is shown in Appendix D:
g) For instruments with thermodynamic melting point measurement function, increase the temperature at a heating rate of 0.2℃/min: measure the thermodynamic melting points of 3 to 8 melting point standard substances. Repeat the measurement three times: the difference between the average value of the two measurements and the thermodynamic melting point standard of the corresponding standard substance is the thermodynamic melting point measurement indication error of the instrument. Calculate using formula (1). 6.3.2.2 Hot-stage melting point determination instrument
a) Sample preparation: Take a dry, clean slide and cover glass, and place an appropriate amount of melting point standard material on the slide: Grind the grains with the cover glass to form a uniform layer of single grains and fill the field of view; b) The initial temperature of the instrument is set at 15°C of the melting point of the low-temperature standard material. When the set temperature is reached, control the heating stage to rise at a rate of 1°C/min;
c) Visually judge the melting point (full melting point) d) Criteria: When observing the phase change process under a microscope, the temperature when the light effect caused by the particles disappears completely is called the full melting point or full melting temperature: For instruments that automatically judge the melting point based on the change in transmittance caused by the phase change, the criteria for judging the melting point (full melting point) are: On the transmittance time change curve, the temperature corresponding to the intersection of the solid-liquid coexistence measurement curve segment and the extension of the entire liquid phase measurement curve segment is taken as the full melting point or full melting temperature; Instruments that automatically measure the melting point are calibrated according to the instrument's indication measurement function; d) For instruments that use an electric positive thermometer to measure the temperature, three melting point standard substances can be used for calibration within the entire measurement range, one of each of the three temperature ranges of (40-100)°C, (100-200)°C, and (200-300)°C; For instruments that use a glass liquid thermometer to measure the temperature, according to the different temperature measurement ranges of each thermometer, it is generally necessary to use two melting point standard substances for calibration in each temperature measurement range; e) Instrument selection l. 0/min heating rate for indication error verification: each melting point standard substance is measured repeatedly, and the difference between the average value of the subsequent measurements and the standard value of the capillary melting point (total melting point) of the standard substance at the corresponding rate is the indication error of the instrument.
6.3.3 Electrical properties of indication
6.3.3.1 Preparation of samples
a) Preparation of samples for capillary melting point determination instrument: same as specified in 6.3.2.1): 4
J.IG 701--2008
b) Preparation of samples for hot stage melting point determination instrument: same as specified in 6.3.2.2a) 1. 6.3.3.2 Verification method for repeatability of indication
a) Set the temperature of the instrument to be 15℃ lower than the melting point of the standard substance. When the set temperature is reached, control the heating stage to heat up at a rate of 1℃/min;
b) Within the measurement range of the instrument, select a standard substance with a melting point. Repeat the measurement for 6 times under the same measurement conditions. The standard deviation is the repeatability of the indication of the instrument: (a, -x)
Where: s
Standard deviation;
Number of measurements:;
First measurement value;
The arithmetic mean of the first and second measurement values.
6.3.4 Linear heating rate error
6.3.4.1 For instruments with solid heating medium and digital temperature display (resolution better than 0.1℃), use the digital thermometer of the instrument to measure the temperature and use a stopwatch to calibrate the linear heating rate: For instruments with liquid heating medium, use a standard platinum resistance thermometer and a digital temperature measuring instrument to calibrate the linear heating rate. Within the range of the instrument, select two points close to the highest and lowest limits for the calibration of linear heating error. 6.3.4.2 The instrument heats up at a heating rate of 1℃/min, and starts timing after (3~-5)min. Record the temperature measurement value once a minute and measure 10 values ​​continuously. 6.3.4.3 Process the two groups of 10 time and temperature measurement values ​​respectively, and calculate the linear heating rate error according to formula (3):
武中,8
Linear heating rate error from the ith minute to the ith minute;T: temperature value measured at the ith minute;
t:—ith minute;
Set linear heating rate 1℃/min;
11, 2,., 10.
After calculating the linear heating rate error point by point, take the largest error as the linear heating rate error. 6.3.5 Insulation resistance
The power plug of the instrument is not connected to the power supply, and the power switch of the instrument is turned on. Use a 500V megohmmeter to apply a 500V DC test voltage between the phase line of the power plug of the instrument and the exposed metal part of the instrument chassis. Measure the insulation resistance after stabilizing for 5s.
6.41 Handling of verification results
6.4.1 All the above verification data shall be recorded in the verification record1, and the relevant items shall be written in full or noted on the verification certificate or verification result notice:
JJG 701—2008
6.4.2 For instruments that meet the technical indicators specified in this regulation after verification, a verification certificate shall be issued (the format of the verification certificate is shown in Appendix B); for instruments that do not meet the technical indicators specified in this regulation, a verification result notice shall be issued (the format of the verification result notice is shown in Appendix C), and the unqualified items shall be pointed out. 6.5 Verification cycle
The verification cycle of the instrument is generally 1 year. During this period, when the conditions change or there is doubt about the measurement results, verification should be carried out.
NHrind
ADOTON
WETROL
Appendix A
A.1 Melting point standard substances
JG 701—2068
Melting point standard substances and instructions for use
Grade A.1 Melting point standard substances and instructions for use. Grade A melting point standard substances are listed in Table A.2. The melting point standard values ​​and uncertainties are based on the standard substance certificates.
A.2 Instructions for use
The melting point standard substances should be dried before use.
A.2.1 Bottled melting point standard substances
A.2.2 Melting point standard substances packaged in capillaries, both ends of the capillaries have been sealed, and the marked end should be broken off before use.
Should be used according to 6.1.
A.2.4 Capillary rubbing
2 Regulations for selecting ball type
Electrode capillary melting point standard quality,
Type a: inner diameter 09~~1.1)mm;
(0.10~0.1m;
Type b: inner sleeve 1.6±0.07)mn;
Thermodynamic melting
Name
p-nitro
benzoic acid
1,f-baric acid
p-methoxybenzoic acid
p-nitrobenzene acid
Length 10f
Length 80°m
Grade melting point standard material standard value
Capillary melting point (full ignition point)
.0.20℃/min
1: ot:&min
p-Nitrotoluene
Benzoic acid
1.6·Adipic acid
p-Toluene-2-cyanobenzoic acid
p-Nitrophenyl acid
Vanillin
Acetanilide
Phesidine
Butyric acid
Sulfadimethoxine
Dicyandiamide
Caffeine
JWG781-2908
Table A. 2 Dipolar melting point standard material standard value Thermodynamic melting point
F=1,A7-0
Note: F-solid amount ± liquid amount,
Liquid amount
AT=sample ambient temperature minus sample temperature,
U-uncertainty (-2).
0.20C/min
Capillary point (full melting point》
1.0℃/min
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