JJG 1012-2006 Calibration Procedure for Online Automatic Monitoring Instruments for Chemical Oxygen Demand (COD) JJG1012-2006 Standard download decompression password: www.bzxz.net
This procedure is applicable to the initial calibration, subsequent calibration and in-use inspection of online automatic monitoring instruments for chemical oxygen demand (COD) with a measurement range of (30~1000) mg/L.

National Metrology Verification Regulation of the People's Republic of China JJG1012-2006
On-line Automatic Determinator of ChemicalOxygenDemand (COD)
2006-05-23 Issued
2006-08-23. Implementation
Issued by the General Administration of Quality Supervision, Inspection and Quarantine JJG1012—2006
Verification Regulation of On-lineAutomatic Determinator of ChemicalOxygenDemand (COD) (COD)
JJG1012—2006
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine on May 23, 2006 and came into effect on August 23, 2006. www.bzxz.net
Responsible unit: National Technical Committee for Environmental Chemical Metrology Drafting unit: Shandong Provincial Environmental Monitoring Center China National Environmental Monitoring Center
This regulation entrusts the National Technical Committee for Environmental Chemical Metrology to be responsible for the interpretation of this regulation Main drafters:
Jin Lisha
Sun Hailin
Participating drafters:
JIG1012—2006
(Shandong Provincial Environmental Monitoring Center)
(China National Environmental Monitoring Center)
(Shandong Provincial Environmental Monitoring Center)
(Shandong Provincial Environmental Monitoring Center)
1 Scope
2 Overview
3 Metrological performance requirements
3.1 Zero drift
3.2 Indication stability
3.3 Indication error
4 General technical requirements
4.1 Appearance| |tt||4.2 Insulation resistance
5 Control of measuring instruments
5.1 Verification conditions
5.2 Verification items
5.3 Verification methods
5.4 Processing of verification results.
5.5 Verification cycle
JJG1012—2006
Appendix Preparation method of ACOD standard solution and traceability to certified reference materials Appendix B Verification record Recording format
Appendix C Verification certificate and verification result notification inner page format ()
1 Scope
JJG1012—2006
Verification procedure for online automatic monitoring instrument for chemical oxygen demand (COD) This procedure is applicable to the initial verification, subsequent verification and in-use inspection of online automatic monitoring instrument for chemical oxygen demand (COD) with a measurement range of (30~1000) mg/L (hereinafter referred to as instrument). 2 Overview
Chemical oxygen demand (COD) refers to the mass concentration of oxygen consumed by the oxidant when the organic matter and inorganic reducing substances in the water sample are oxidized by a strong oxidant under certain conditions. COD reflects the degree of pollution of the water body by organic matter and inorganic reducing substances.
The instrument uses a computer to automatically control water sample collection, digestion and oxidation, reaction measurement, data processing and data transmission, and quickly and continuously completes the whole process of COD analysis in wastewater. The instrument has been widely used in enterprise sewage outlets and urban sewage treatment plants.
The instrument can be divided into two types according to the different redox modes. The first type is designed according to the oxidation principle of GB11914-1989 (Determination of Chemical Oxygen Demand of Water Quality - Potassium Dichromate Method). That is, a known amount of potassium dichromate solution is added to the water sample, and the organic matter and reducing substances in the water sample are oxidized under strong acid heating. The detection unit can use photoelectric colorimetry, coulometric titration, and redox titration to complete the determination and data processing. The instrument directly displays the COD concentration in the water sample. The second type is designed according to the principle of electrochemistry. That is, the measuring electrode can be used to electrolyze and produce hydroxyl radicals and ozone under constant voltage conditions. Hydroxyl free radicals and ozone can directly oxidize organic matter and reducing substances in the water sample in the reaction tank, and the electrolysis current value of the generated hydroxyl free radicals and ozone is proportional to the concentration of reducing substances in the water sample. Using the measuring electrode in the water This special change in the sample is detected by the detection unit through the change of current on the measuring electrode to complete the measurement and data processing. After calibration, the instrument directly displays the concentration of COD in the water sample. Both types of instruments are composed of automatic sampling unit, reaction unit, detection unit, data processing unit, display and recording unit, data transmission, etc.
The structure of the instrument is shown in Figure 1.
Electrolytic cell
Group product meter version
Oxidation reaction
Test measurement
Detector
Liquid extraction
Figure 1 Schematic diagram of instrument filing
Display record
Data transmission
3 Measurement performance requirements
3.1 Zero drift
Do not exceed ±5mg within 4h /L.
3.2 Indication stability
Not more than ±10% within 24h
3.3 Indication error
The indication error shall not exceed 10%.
4 General technical requirements
4.1 Appearance
JJG1012—2006
The instrument shall have the following markings: instrument name, model, factory number, manufacturing date, manufacturer name, working voltage and frequency, manufacturing license mark (domestic instruments) and number, etc. An instruction manual shall be attached. The instrument shall not have mechanical damage that may hinder normal operation: each regulator shall rotate flexibly and be accurately positioned: each fixing shall not be loose: after power-on, the digital display shall be complete and clear. 4.2 Insulation resistance
The insulation resistance of the instrument shall not be less than Hand 20MO.
5 Measuring instrument control
Measuring instrument control includes: initial calibration, subsequent calibration and in-use inspection. 5.1 Calibration conditions
5.1.1 Calibration equipment
5.1.1.1 Zero calibration solution: Add a small amount of potassium permanganate to the distilled filling water (the purple-red color of potassium permanganate in the water should always be kept unchanged during the distillation process, otherwise potassium permanganate should be added in time). 5.1.1. The uncertainty of 250, 150, 500 mg/L COD standard solution should not be greater than 3% (starting at = 2). 5.1.1.3 Insulation resistance meter: 500V, 10 levels. 5.1.2 Environmental conditions
5.1.2.1 Environmental temperature: (5-40) C.
5.1.2.2 Environmental humidity: ≤90% RH.
5.1.2.3 Power supply: AC (220 ± 22) V: (50 ± 1) Hz. 5.1.2.4 Electromagnetic field interference and vibration that do not affect the normal operation of the instrument should be avoided from corrosive gases. 5.2 Verification items
Verification items are shown in Table 1.
Verification items
Zero drift
Indication stability
Indication error
Insulation resistance
JJG1012—2006
Table 1 List of verification items
First verification
Note: 1. "+" is a potential inspection item, and "-" is an item that can be ignored. Subsequent verification
In-use inspection
2. If the installation and maintenance have a significant impact on the metering performance of the instrument, the subsequent verification must be carried out in conjunction with the initial verification items. 5.3 Verification method
5.3.1 Preparation before verification
5.3.1.1 Preheat the instrument and run it stably according to the requirements of the instrument manual. 5.3.1.2 Calibrate the instrument according to the requirements of the instrument manual. 5.3.2 Appearance
Inspect by visual inspection and touch.
5.3.3 Insulation resistance
Do not connect to the power supply, the instrument power switch is in the on position, and the terminals of each circuit are short-circuited. Connect the terminals of the insulation resistance meter to the AC input terminal and the charger of the instrument respectively, apply 500V DC voltage, and read the insulation resistance value after stabilization for 10s.
5.3.4 Zero drift
According to the requirements of the instrument manual, after the instrument runs stably, introduce the zero calibration liquid, record the initial zero value Z (mg/L) of the measurement, and record the zero indication Z. (mg/L) every 30min within 4h. Take the zero point indication Z with the largest deviation from Z. Calculate the zero point drift 4Z of the instrument according to formula (1). AZ= Zmx-Zo
5.3.5 Indication stability
According to the requirements of the instrument manual, after the instrument is running stably, introduce 500mgL standard solution, record the initial measurement value Sm (mg/L), and run it continuously for 24h. Record the measurement value S (mg/L) every 1h within 24h. Take the measurement value S with the largest deviation from S.Calculate the indication stability AS according to formula (2). Smr-Se×100%
Wherein: S—initial measurement value of 500mg/L standard solution, mg/L; S—the maximum measurement value that deviates from S within 24h, mg/L(2)
5.3.6 Indication error
JJG 1012—20H06
According to the requirements of the instrument manual, after the instrument is running stably, introduce COD standard solutions with mass concentrations of 50, 150, and 500mg/L in turn for measurement. Each solution is measured continuously for 3 times. Calculate the indication error AC according to formula (3).
Where: AC indication error:
CC.×100%
C3 times measurement average value, mg/L:
CCOD standard solution mass concentration value, mg/L The maximum calculated value in the indication error AC is the indication error calibration result of the instrument. 5.4 Processing of calibration results
Instruments that pass the calibration according to the requirements of this regulation shall be issued with a calibration certificate: instruments that fail the calibration shall be issued with a calibration result notice and the unqualified items shall be noted.
5.5 Calibration cycle
The calibration cycle shall generally not exceed 1 year.
Appendix A
JJG1012-2006
Preparation method of COD standard solution and its comparison with certified reference material A.1 Preparation method of COD standard solution
A.1.1 Weigh 0.4251 g of potassium hydrogen phthalate (reference reagent) which has been dried at 120°C for 2 hours and cooled, and dissolve it in a small amount of re-distilled water. Transfer the whole amount into a 1000 mL volumetric flask and dilute it to the mark with re-distilled water to make it a 500 mg/L OOD standard liquid. Prepare it fresh when using. A.1.250, 150 mg/L COD standard solutions are obtained by diluting this solution step by step. A.2 The prepared COD standard solution value should be traced back to the certified standard substance A.2.1 Absorb 100mL of COD standard solution with a mass concentration of 500mg/L and place it in a 500mL volumetric flask, add heavy distilled water to dilute to the mark, mix and prepare a COD standard solution with a mass concentration of 100mg/L. A.2.2 According to the requirements of the instrument manual, after the instrument is running stably, introduce the above-mentioned COD standard solution with a mass concentration of 100mg/L and the purchased COD certified standard substance solution with a mass concentration of 100mg/L (such as standard substance number: GBW (E) 080273) in turn for measurement. Each solution is measured 6 times in a row, and the measured values ​​are recorded respectively. A.2.3 Compare the two groups of measured values. If the difference meets the following formula, it proves that the prepared COD standard solution value can be traced back to the certified standard substance.
IY-Y≤VU+U.
Wherein: Y is the arithmetic mean of the six measurements of the prepared standard solution; Y is the arithmetic mean of the six measurements of the certified standard substance: U.——the expanded uncertainty of the prepared standard solution (&=2); U. —the expanded uncertainty of the certified standard substance (=2). 5
Appendix B
Instrument name and model only:
Testing unit:
Testing environment: temperature and humidity
JJG 1012—2006
Testing record format
Manufacturer name:
Factory (or instrument) number:
Testing record number:
Insulation resistance:
Initial zero value Z. (mg/L):
Stability
Indication error
Inspector
Time/min
Zero point indication 2./(mg/L）
Zero point source shift A2/(mg/L）
Initial measurement value S.(mg/L):
Time/h
Secondary value S./(mg/L)）
Time/h
Fewer value S./(mg/L）
Indication stability 4S/%
COD standard solution/(mg/L)
Indication error 4C/%
Inspection conclusion
Inspector
Inspection date
Average Value/(mg/L)
Appendix C
JJG1012—2006
Inner page format of verification certificate and verification result noticeInner page format of verification certificate
Verification results
Verification items
Zero point drift
Indication stability
Indication error
Insulation resistance
C.2 Inner page format of verification result notice
Unqualified items:
Verification items
Zero point source drift
Indication stability
Insulation resistance
Technical requirements
Technical requirements
Verification results
Verification results/(mg/L）
Indication stability 4S/%
COD standard solution/（mg/L）
Indication error 4C/%
Verification conclusion
Verifier
Verification date
Average value/（mg/L）
Appendix C
JJG1012—2006
Format of the inner page of the verification certificate and the notification of verification resultsFormat of the inner page of the verification certificate
Verification results||t t||Verification items
Zero point drift
Indication stability
Indication error
Insulation resistance
C.2 Format of the inner page of the verification result notice
Unqualified items:
Verification items
Zero point source drift
Indication stability
Indication error
Insulation resistance
Technical requirements
Technical requirements
Verification results
Verification results/(mg/L）
Indication stability 4S/%
COD standard solution/（mg/L）
Indication error 4C/%
Verification conclusion
Verifier
Verification date
Average value/（mg/L）
Appendix C
JJG1012—2006
Format of the inner page of the verification certificate and the notification of verification resultsFormat of the inner page of the verification certificate
Verification results||t t||Verification items
Zero point drift
Indication stability
Indication error
Insulation resistance
C.2 Format of the inner page of the verification result notice
Unqualified items:
Verification items
Zero point source drift
Indication stability
Indication error
Insulation resistance
Technical requirements
Technical requirements
Verification results
Verification results
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