JJF 1224-2009 Calibration specification for steel bar cover and floor thickness measuring instrument JJF1224-2009 Standard compression package decompression password: www.bzxz.net
This specification is applicable to the calibration of steel bar cover thickness measuring instrument and floor thickness measuring instrument.

This specification refers to the following documents:
JJF1001—1998 General metrological terms and definitions
JJF1059—1999 Evaluation and expression of measurement uncertainty
JJF1094—2002 Evaluation of measuring instrument characteristics
GB50204—2002 Code for acceptance of construction quality of concrete structure engineering
When using this specification, attention should be paid to the use of the current valid versions of the above-mentioned referenced documents.
1 Scope (1)
2 References (1)
3 Terminology (1)
4 Overview (1)
5 Metrological characteristics (1)
5.1 Measurement repeatability (1)
5.2 Indication error (1)
6 Calibration conditions (3)
6.1 Environmental conditions (3)
6.2 Calibration standards (3)
7 Calibration items and calibration methods (3)
7.1 Measurement repeatability (3)
7.2 Indication error (4)
8 Expression of calibration results (4)
8.1 Calibration certificate (4)
8.2 Measurement uncertainty of calibration results (4)
9 Recalibration time interval (4)
Appendix A Evaluation of the uncertainty of the measurement results of the indication error of the steel bar cover thickness measuring instrument (5)
Appendix B Technical requirements for standard blocks (7)
Appendix C Contents of calibration certificate (8)

National Metrology Technical Specification of the People's Republic of China J.IF 1224—2009
Calibration Specification for Reinforced Concrete Covermeter andFlorslab Thickress Tester
2009-07—10 Issued
2009 — 10 — 10 Implementation
Issued by the General Administration of Quality Supervision, Inspection and Quarantine JJF 1224--2009
Calibration Specification for Reinforced ConcreteCovermeter and Floorslab Thickness TesterJJF12242009
This specification was approved by the General Administration of Quality Supervision, Inspection and Quarantine on July 10, 2009, and will be implemented from October 10, 2009.
Responsible unit: National Technical Committee on Geometry Engineering Parameters Main drafting unit: China Institute of Metrology Beijing Institute of Metrology and Testing Science
Guangdong Institute of Metrology
Shanghai Institute of Measurement and Testing Technology
Beijing Zhibolian Technology Co., Ltd.
Participating drafting unit: China Institute of Testing Technology Hilti (China) Co., Ltd.
This specification is interpreted by the National Technical Committee on Geometry Engineering Parameters Main drafter of this specification:
J.IF 1224—2009
Zhang Heng (China Institute of Metrology)
Wu Xun (Beijing Institute of Metrology and Testing Science) Zhang Yong (Beijing Institute of Metrology)
Liao Yin (Shanghai Institute of Metrology and Testing Technology) Guan (Beijing Zhibolian Technology Co., Ltd.) Participating drafters:
Ran Qing (China Institute of Testing Technology)
Wang Conghui (Hilti (China) Co., Ltd.) 1 Scope·
References
3 Terminology·
4 Overview·
5 Planning Quantitative characteristics
Measurement repeatability·
5.2 Indication error,
6 Calibration conditions,
6.1 Environmental conditions
6.2 Calibration standard blocks
7 Calibration items and calibration methods
Measurement repeatability·
7.2 Indication error
8 Expression of calibration results
8.1 Calibration certificate·
8.2 Measurement uncertainty of calibration results:
9 Recalibration time interval·
Appendix A
J.IF 1224—2009
Uncertainty evaluation of indication error of steel bar cover thickness measuring instrument Appendix B Technical requirements for standard blocks
Contents of calibration certificate
Appendix C
(3)
1 Scope
JJF1224--2009
Calibration specification for steel bar cover thickness measuring instrument and floor slab thickness measuring instrument This specification is applicable to the calibration of steel bar cover thickness measuring instrument and floor slab thickness measuring instrument. 2 References
This specification references the following documents:
JJF1001—1998 General metrological terms and definitions JIF1059-1999 Evaluation and expression of measurement uncertainty JF1094-2002 Evaluation of measuring instrument characteristics
GB502042002 Specification for acceptance of concrete structure construction quality When using this specification, attention should be paid to using the current valid versions of the above-mentioned references. 3Terms
Thickness of the concrete protective coating: refers to the distance from the outer edge of the steel bar to the surface of the H protective layer.
4Overview
The steel bar protective layer and floor thickness measuring instrument refer to the steel bar protective layer thickness measuring instrument and the floor thickness measuring instrument. They are instruments that use electromagnetic principles for non-destructive testing and are used for detecting the thickness of the concrete protective layer of building structures and measuring the thickness of floor slabs.
The probe (with transmitting and receiving functions) of the steel bar protective layer measuring instrument transmits electromagnetic signals, and the steel bars in the protective layer generate secondary induced magnetic fields, which are received by the probes. After being processed by the instrument, the thickness of the steel bar protective layer or the diameter of the steel bar is obtained. The instrument can also be used to measure the distribution of steel bars. The transmitting and receiving probes of the floor thickness measuring instrument are placed on the surface and bottom of the measured floor slab respectively. The transmitting probe transmits electromagnetic signals, and the receiving probe receives the magnetic field after being inducted: after being processed by the instrument, the thickness measurement value of the floor slab is obtained. The schematic diagrams of the instrument principles are shown in Figures 1 and 2 respectively. 5 Metrological characteristics
5. Measurement repeatability
The requirements for the repeatability of the steel bar cover thickness measuring instrument are shown in Table 1, and the requirements for the repeatability of the floor slab thickness measuring instrument are shown in Table 2.
5.2 Indication error
5.2.1 Steel bar cover thickness measuring instrument
The maximum allowable error of the indication of the steel bar cover thickness measuring instrument is divided according to the thickness of the steel bar cover being measured, and the requirements are shown in Table 1.
Rebar protective layer thickness measuring instrument
JJF 12242(H09
Moving position of probe
Figure 1 Schematic diagram of principle of rebar protective layer thickness measuring instrument Floor thickness measuring instrument
Receiving probe
Transmitting probe
Figure 2 Schematic diagram of principle of floor thickness measuring instrument
Table 1 Measuring characteristics of rebar protective layer thickness measuring instrument Requirements for calibration items
Measurement repeatability
Indication error
Note: H.
Forged bar diameter d
(destroyed birch)
Protective layer thickness H
Maximum allowable error
-instrument measurement lower limit, Hs--
5.2.2 Indication error of rebar diameter
Technical requirements
Imm (HeHs40mm)
(8~12)
(14-20) ml
Protective layer thickness
40mmH60mm
Instrument measurement upper limit, n1.
Maximum allowable error of steel bar diameter measurement: soil 1 steel bar diameter specification, 5.2.3 Floor thickness measuring instrument
± (1mm+3%I)
The maximum allowable error of the floor thickness measuring instrument is divided according to the floor thickness, and the requirements are shown in Table 2. 2
Calibration item date
Measurement repeatability
Indication error
Note: H-
JJF 12242009
Table 2 Requirements for metrological characteristics of floor thickness measuring instrument Technical requirements
1mm (floor thickness ≤200rm)
Floor thickness
Maximum allowable error
Floor thickness, mm.
Note: The above metrological characteristics are for reference only. Calibration conditions
6.1 Environmental conditions
.200rmrml
6.1.1 The requirements for laboratory temperature, humidity and equilibrium temperature time are shown in Table 3. Table 3 Calibration conditions
Calibration room overflow (℃)
Current overflow change (℃/h)
Relative condensation (%)
-200mm
±(1mm+1%H)
Time for the calibrated instrument to balance
temperature in the room (h)
The laboratory should avoid interference from strong alternating electromagnetic fields or close alternating magnetic fields (stroke machines, electric welders, etc.).
6.1.3 During measurement, the measuring point should be within 500m There should be no large metal structure. 6.2 Calibration standard block
For the technical requirements of calibration standard block, see Appendix B. 7 Calibration items and calibration methods
First check the appearance and make sure there are no factors that affect the calibration measurement characteristics before calibration. 7.1 Measurement repeatability
7.1.1 Steel bar cover thickness measuring instrument
Select threaded steel bars with a diameter of 12mm and standard blocks with a cover thickness greater than the instrument's measurement limit and not exceeding 40mm to calibrate the instrument's measurement repeatability. Set up and initialize the instrument according to the instrument manual. Continuously and repeatedly measure the standard block 9 times while measuring the cover thickness. Take one-tenth of the difference between the maximum and minimum values ​​of the 9 readings as the calibration result. 7.1.2 Floor Thickness Measurement
Select a steel bar standard block with a thickness of 1501μm to calibrate the measurement repeatability of the instrument. Set and initialize the instrument according to the instrument manual. When measuring, ensure that the center lines of the transmitting and receiving probes on both sides of the standard block coincide. Continuously and repeatedly measure the standard block 9 times, and take one-third of the difference between the maximum and minimum values ​​in the 9 readings as the calibration result.
7.2 Indication Error
7.2.1 Example of Steel Bar Sheath Thickness Measurement
7.2.1.1 Indication Error of Sheath Thickness
JJF 1224—2009
Select calibration points based on the steel bar diameter range and its corresponding protective layer thickness measurement range shown in Table 1. Select a steel bar of one specification within the steel bar diameter range, and select 3 calibration points within its corresponding protective layer thickness measurement range. Before measurement, set up and initialize the instrument according to the instrument manual. When measuring, take the average of 3 readings at each calibration point as the measured value of the point: the difference between the measured value and the actual value of the standard block is the indication error of the point, and take the indication error with the largest absolute value of the indication error of each point as the calibration result. 7.2.1.2 Indication error of steel bar diameter
According to the steel bar diameter range in Table 1, select 3 steel bars of different specifications, set up and initialize the instrument according to the instruction manual, measure the diameter of each steel bar 3 times during measurement, take the difference between the average value and the nominal value of the steel bar diameter as the indication error of the point, and take the smallest error with the largest absolute value of the indication error of each point as the calibration result. 7.2.2 Floor thickness measuring instrument
According to the floor thickness measurement range shown in Table 2, evenly select 3 calibration points within the measurement range. Before measuring, set up and initialize the instrument according to the instructions. When measuring, ensure that the center lines of the transmitting and receiving probes on both sides of the standard block coincide. Measure the thickness of the standard block. Take the average of 3 readings at each point as the measured value of the point. The difference between the measured value and the actual value of the standard block is the indication error of the point. Take the indication error with the largest absolute value among the indication errors of each point as the calibration result.
8 Expression of calibration results
8.1 Calibration certificate:
A calibration certificate shall be issued for the calibrated steel bar cover thickness measuring instrument and floor slab thickness measuring instrument. The calibration certificate shall contain the calibration results of measurement repeatability and indication error and their measurement uncertainty (see Appendix (). 8.2 Measurement uncertainty of calibration results
The uncertainty of the calibration results of the steel bar cover thickness measuring instrument and the floor slab thickness measuring instrument shall be evaluated in accordance with the requirements of JJF1059-1999. For examples of uncertainty evaluation, see Appendix A. 9 Recalibration time interval
The recalibration time interval of the steel bar cover thickness measuring instrument and the floor slab thickness measuring instrument shall be determined by the user according to the on-site usage conditions. It is recommended that it should not exceed 1 year.
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Appendix A
JIF 1224-2009
Uncertainty assessment of the indication error measurement results of the steel bar protective layer thickness measuring instrument First, set up and initialize the measuring instrument according to the instruction manual, and then calibrate the instrument with a single steel bar standard block. The difference between the average value of the instrument indication and the actual value of the standard block is the indication error A. This paper takes the calibration point with a protective layer thickness of 40mm and a steel bar diameter of 12mm as an example: the uncertainty assessment of the indication error measurement method of the steel bar protective layer thickness measuring instrument proposed in the text is carried out. A.1 Mathematical model
A—h—ha
武: A
Indication error of the steel bar protective layer thickness measuring instrument, mm:h一. The thickness value displayed by the calibrated instrument, inim;h. The serial value of the standard block, mm.
A.2 Variance and sensitivity coefficient
ux(y) = [af/ax,u(x,)
u --u\(A)=c\(h) + u(h)+e(h,) *(h)H: t(h)-aa/ah=1,c(hg)=aa/ang -—1. Substituting:
ue-u(h) u'(h,)
A.3 Standard uncertainty--table
Table A.1 Standard uncertainty table
Standard uncertainty
Component u(r)
Uncertainty source
Uncertainty component related to instrument end reading Quantization error of measurement basis
Measurement repeatability
Uncertainty component related to standard block
Standard block thickness value error
Uncertainty of parallelism
Uncertainty of steel bar diameter
Standard uncertainty value
w(a,(nm)
0. 5//3=0. 29
1/(2.97×/3)=0.19
0.3/,/3-0. 17
0. 1//3 -0. 06Www.bzxZ.net
0.15//3-0. 09
--0. 1241mm2 ; ±,=0. 35mm
A.4 Calculation of standard uncertainty
A.4.1 Uncertainty component related to instrument reading () product
(:(mm)
A.4.1.1 Uncertainty component u (h) introduced by the quantization error when calibrating the reading of the steel reinforcement thickness measuring instrument 5
JJF 1224—2009
The quantization error of the reading of the steel bar protective layer thickness measuring instrument with a resolution of 1mm appears with equal probability in the area with a half width of (1/2)nm: Release:
w(h,)=0.5mm//3=0.29nm
A4.1.2 The uncertainty component introduced by the measurement repeatability is calculated by the range method of 9 repeated measurements, -2.9? , take the average of 3 readings as the measurement result, then:
u(h2)=1mm/(2.97X/3)=--0.19mm The measurement repeatability is less than the quantization error (resolution) of the instrument, and the uncertainty component related to the instrument reading takes the quantization error (resolution), and we get:
w(h)-—0.29nr
A.4.2 Uncertainty component u(h.) related to the standard block A.4.2.1 Uncertainty component introduced by the standard block sequence value error (h,) The original value of the standard block used is 40nmim. According to the requirements of Appendix B (the small size tolerance of the standard block is ±0.3mm), the uncertainty of the thickness value estimate is Component: u(h.,)=0.3rmm//3-0.17mml
A.4.2.2 Uncertainty component (wz) caused by the parallelism between the surface of the standard block and the steel screen According to the requirements of Appendix B (parallelism is not greater than 0.2mm), the parallelism between the surface of the standard block and the steel bar should not exceed 0.2mm. According to the uniform distribution with a half-width of 0.1mm, the uncertainty component is estimated as: u(ha.,)-0.1mm//3-0.06mm
A.4.2.3 Uncertainty component (uha) caused by the dimensional deviation of the steel bar diameter The manufacturing deviation of the steel bar diameter does not exceed ±0.15rrtn. According to the uniform distribution, then: uth.,=0. 15mm//3=0.09mm
(h,) u(hg,)+u(ha)+u(ha)
Calculation: z(h,)/(0.17mm)2+(0.06mm)2-+(0.09mm)2=0.20mmA.5 Synthesized standard uncertainty
There is no correlation worth considering among the above uncertainty components. The above uncertainty components are synthesized according to the following formula:
u.-z(h)\-+u(ha)2=(0.29mm)2+(0.20mm)2-0.124lmm2u,-0. 35mml
A.6 Expanded uncertainty
Take the inclusion factor as 2, then:
[J --ku2X0. 35mm-0. 7mm
A.7 Measurement uncertainty report
Through the above measurement uncertainty assessment, it can be seen that the expanded uncertainty is obtained from the standard uncertainty, -2, standard uncertainty:
Expanded uncertainty:
u.=0.35mm
U--0.7mm (k=2)
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Appendix B
B.1 Standard block material
B.1.1 Coating material
Non-magnetic material is selected,
JJF1224—2009
Technical requirements for standard blocks
B1.2 Technical requirements for steel bar size, material composition, etc. for standard blocks are shown in Table B.1. Table B.1
Technical requirements
Rebar diameter range
Diameter tolerance
Appearance shape
Remarks: 1.The steel bar has not been subjected to mechanical tests such as drawing, and the surface has not been chemically corroded; 2. It complies with GB50010-2002 and GB1499,2-2007. B.2 Technical requirements of standard steel bars
8mm~-50mm
According to the relevant national standards
HR13335 threaded steel bars
B.2.1 The flatness of the working surface of the standard block is greater than 0.04mm, and the parallelism relative to the working surface is not greater than 0.1mm; B.2.2 The standard block is composed of a covering layer and a single steel bar. The standard block with a thickness greater than the floor slab thickness may not be reinforced: the parallelism between the working surface of the standard block and the axis of the steel bar is not greater than 0.2mm; B.2.3
The dimensional tolerance of the standard block is ±0.3mm.
The standard block can be made into a separate or integrated type, and the structural diagram is shown in Figures B1 and 2. H3
Non-magnetic materials
Non-magnetic materials
Content support blocks
Non-magnetic materials
Working tables
Standard test blocks for separable steel bar protection layer
Thickness of steel bar protection layer
Non-ethereal materials
Standard test blocks for integral steel bar protection layer
Figure 132
Appendix C
1. Title: Calibration Certificate;
2. Name and address of laboratory:
JJI 1224-2009
Contents of calibration certificate
3. Unique identification of the certificate or report (such as number), identification of each page and total number of pages4. Name and address of the unit submitting the calibration;
5. Description and clear identification of the object being calibrated;6. 8. Traceability and validity of the measurement standards used in this calibration; 9. Description of the calibration environment; 10. Calibration results of measurement repeatability and indication error and their measurement uncertainty; 11. Signature or equivalent identification of the issuer of the calibration certificate or calibration report, and the date of issue; 12. Statement that the calibration results are valid for the calibrated object; 13. Statement that the certificate may not be partially reproduced without the written approval of the calibration laboratory.
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