(1) National Physical Laboratory (NPL), New Delhi
Functions and Responsibilities
The National Physical Laboratory (NPL) in New Delhi is India’s premier institution for metrology, functioning under the Council of Scientific and Industrial Research (CSIR). Its key roles include:
Maintaining National Measurement Standards: NPL establishes and maintains India’s primary standards of physical measurements, ensuring uniformity in measurements across the country.
Calibration Services: It provides high-accuracy calibration services for industries, research institutions, and government agencies.
Scientific Research and Development: Engages in R&D related to precision measurements, new materials, and advanced metrology techniques.
Quality Assurance and Standardization: Works with organizations like BIS (Bureau of Indian Standards) to set national standards for various measurements.
Support for Industry and Trade: Helps Indian industries achieve international measurement accuracy required for exports and global trade.
Environmental and Atmospheric Studies: Conducts research in areas like air pollution monitoring, material testing, and quantum metrology.
Relationship with International Standards
BIPM (International Bureau of Weights and Measures): NPL aligns India’s measurement standards with SI units maintained by the BIPM.
OIML (International Organization of Legal Metrology): Ensures that Indian legal metrology standards comply with global norms.
ISO/IEC 17025 Compliance: NPL operates its calibration laboratories in compliance with ISO/IEC 17025, which defines general requirements for testing and calibration.
Mutual Recognition Agreements (MRA): Participates in CIPM MRA, ensuring global acceptance of Indian calibration and measurement certificates.
(2) Regional Reference Standard Laboratories (RRSLs)
India has multiple Regional Reference Standard Laboratories (RRSLs) located in Ahmedabad, Bangalore, Bhubaneswar, Faridabad, and Guwahati. These labs function under the Legal Metrology Division of the Department of Consumer Affairs.
Definition and Purpose
Definition: RRSLs are specialized laboratories designated to maintain reference standards at the regional level. They act as an intermediary between NPL (national standards) and state or industrial standards.
Purpose:
Calibration and Verification: Provide calibration services to weights and measures used in industries, research, and commerce.
Traceability to National Standards: Ensure all regional and state-level measurements are traceable to NPL’s national standards.
Support for Legal Metrology: Assist in the enforcement of the Legal Metrology Act, 2009, ensuring fair trade practices.
Calibration Processes
The calibration process at RRSLs involves:
Receiving Instruments: Weighing machines, pressure gauges, flow meters, thermometers, and other measuring instruments from industries and government agencies.
Preliminary Inspection: Checking for visible damage or defects.
Comparison with Reference Standards: Instruments are tested against high-accuracy reference standards maintained at RRSL.
Measurement Correction & Adjustment: If deviations are found, adjustments are made to ensure accuracy.
Issuance of Calibration Certificates: Provides traceable calibration certificates recognized under ISO standards.
Calibration Periodicity – All measuring instruments must be recalibrated every five years to maintain accuracy and compliance with legal metrology regulations.
Relationship with National Standards
Traceability: RRSLs derive their standards from NPL, ensuring hierarchical calibration—from primary standards to working standards used in industries.
Bridging National and Industrial Calibration Needs: While NPL maintains the highest-level measurement standards, RRSLs provide practical calibration and verification services for local industries and state governments.
Legal Metrology Support: Assists in implementing national measurement regulations, ensuring compliance with BIS and international measurement norms.
(3) Secondary Standard Laboratory (Kakkanad, Ernakulam)
Definition and Purpose
A Secondary Standard Laboratory (SSL) is a facility responsible for maintaining, calibrating, and disseminating measurement standards that are traceable to primary or reference standards. These laboratories ensure the accuracy and reliability of measuring instruments used in industries, research institutions, and legal metrology.The Central Laboratory of Legal Metrology (CLLM) is located at Legal Metrology Bhavan, Kakkanad, Ernakulam and serves as the custodian of Secondary Standards in Kerala. It is India’s only NABL-accredited Secondary Standards Laboratory, ensuring internationally recognized measurement accuracy and reliability.
Functions of CLLM:
Custody of Secondary Standards – Safeguards and maintains the secondary standards of Kerala.
Maintain the Secondary Standards Laboratory – Houses and operates precision measurement equipment.
Verification & Certification –
Calibrates and certifies working standards used in Legal Metrology offices.
Verifies check measures used by Assistant Controllers.
Traceability to Reference Standards – Periodically verifies and certifies Secondary Standards with:
Regional Reference Standards Laboratory (RRSL)
National Physical Laboratory (NPL), India
Training & Capacity Building – Conducts training on maintenance and calibration of Working Standards.
Inspection of Working Standard Laboratories – Performs frequent audits to ensure compliance.
Specialized Facilities at CLLM:
Sphygmomanometer Verification Laboratory – Calibrates blood pressure measuring devices.
Water Meter Verification – Provides calibration for municipal and industrial water meters.
Thermometer Calibration – Ensures accuracy in temperature measurement.
Gold Assaying and Testing Laboratory (GATL) –Gold Assaying for bullion, alloys, and jewelry to determine putity and composition.
Relationship with Reference Standard
To maintain accuracy, Secondary Standard Weights at CLLM, Kakkanad are periodically calibrated against Regional Reference Standards Laboratories (RRSLs) and Fluid Control Research Institute (FCRI), which serve as an intermediary between NPL, India, and state-level metrology laboratories. For South India, the relevant RRSL is located in Bangalore, Karnataka. This laboratory ensures that secondary standard weights in Kerala remain traceable to the national reference maintained by NPL, India.
Traceability Of Standards
International Prototypes
↓
National Prototypes
(NPL, New Delhi)
↓
Reference Standards
(RRSL, Bangalore)
↓
Secondary Standards
(Secondary Standard Laboratories, In all States)
↓
Working Standards
(Legal Metrology Offices)
↓
Commercial Weights/Measures
(Shops & other trade premises)
Calibration Process
Calibration ensures that an instrument’s measurements are accurate and traceable to a known standard. The CLLM in Kakkanad follows a rigorous calibration process to maintain accuracy and compliance with legal metrology standards.
Steps in Calibration:
Selection of Equipment – Instruments (e.g., weighing balances, thermometers, sphygmomanometers) are selected for calibration.
Reference Standard Setup – Secondary standards (traceable to RRSL) are used for comparison.
Measurement & Error Identification – Instruments are tested against the standard under controlled conditions.
Adjustment & Correction – Any deviation from the standard is corrected.
Issuance of Calibration Certificate – A certificate is provided, detailing:
Measurement accuracy
Uncertainty values
Traceability to national standards
Rule 31(2) of the Legal Metrology (National Standards) Rules, 2011 clearly states that every Secondary Standard shall be verified against the appropriate Reference Standard by the Reference Standards Laboratory, at an interval not exceeding two years. The Secondary Standard balances shall be verified at least once, within a period of twelve months.
(4) Working Standard Laboratory (Every Inspector Office)
Definition and Purpose
A Working Standard Laboratory is a facility established at every Legal Metrology Inspector Office to ensure the accuracy and reliability of measuring instruments used in trade, commerce, and industry. These laboratories maintain working standards, which are periodically calibrated against secondary standards to ensure consistency in measurements across various sectors.
Purpose of a Working Standard Laboratory:
Verification of measuring instruments used in trade and industry.
Calibration of commercial weighing and measuring devices to ensure compliance with legal metrology regulations.
Prevention of fraudulent practices in measurement-based transactions.
Traceability to secondary standards, ensuring accuracy at the local level.
Calibration Process
The calibration of working standards is an essential process to ensure their accuracy before being used for verifying trade-related measuring instruments. The calibration process follows a systematic approach:
Steps in Calibration of Working Standards:
Selection of Working Standards – Weights, volumetric measures, length measures, and other instruments used for verification are identified.
Comparison with Secondary Standards – The working standards are calibrated against secondary standard weights and measures maintained at the Central Laboratory of Legal Metrology (CLLM), Kakkanad.
Error Measurement and Adjustment – Deviations are recorded, and necessary adjustments are made to bring the working standards within permissible tolerance limits.
Issuance of Calibration Certificates – Once calibrated, a certificate of accuracy is issued, ensuring traceability to secondary and regional reference standards.
Periodic Recalibration – The calibration of working standards is required to be carried out once every year to maintain their accuracy.
Relationship with Secondary Standard
The accuracy and reliability of working standards depend on their traceability to secondary standards, which are maintained at state-level metrology laboratories like CLLM, Kakkanad. Thus, working standards act as the practical tools used by inspectors to verify commercial measuring devices, ensuring that businesses and consumers receive accurate and fair measurements.
Function in Industry
Working Standard Laboratories play a crucial role in ensuring fairness and accuracy in industries that rely on precise measurements. Their primary functions in the industry include:
Verification of Weighing and Measuring Instruments – Ensuring accuracy in commercial weighing scales, petrol pumps, taximeters, and other metering devices.
Consumer Protection – Preventing measurement fraud in trade and ensuring fair transactions in retail, wholesale, and manufacturing sectors.
Enforcement of Legal Metrology Regulations – Ensuring compliance with standards set by the Legal Metrology Act, 2009 and other regulations.
Support for Industrial and Commercial Operations – Assisting industries that depend on precise measurement, such as food production, pharmaceuticals, and construction.
Periodic Inspections – Conducting on-site inspections in markets, fuel stations, and manufacturing units to ensure that measuring devices meet legal standards.
Example Applications
The impact of Working Standard Laboratories extends across various industries and commercial sectors:
Weighing scales in grocery stores and markets – Ensuring that customers receive the correct weight for goods purchased.
Weighbridges for bulk material trade – Verifying the accuracy of large-scale industrial weighing systems.
Petrol Pumps and Diesel Stations – Checking the accuracy of fuel dispensing meters to prevent fraud.
Gas Cylinder and CNG Dispensers – Ensuring proper volume measurements in LPG and CNG refilling stations.
Pharmaceutical Industry – Verifying precision balances for drug formulation.
Textile and Apparel Industry – Calibrating length measurement tools for fabric cutting and sizing.
Construction and Engineering – Ensuring accurate measurement of materials like cement, sand, and steel.
Taximeters in Public Transport – Ensuring that passengers are charged fairly for distances traveled.
Railway and Air Cargo Weighing Systems – Verifying weight accuracy for logistics and freight operations.
Hospital Weighing Machines – Ensuring accuracy in patient weight measurements.
Sphygmomanometers (BP Monitors) – Calibrating devices used in medical diagnostics
(5) Water Meter Testing Labs (Central Laboratory, Kakkanad, Ernakulam)
Functions in Industry
The Water Meter Testing Lab at the Central Laboratory of Legal Metrology (CLLM), Kakkanad, Ernakulam, plays a crucial role in ensuring the accuracy, reliability, and legal compliance of water meters used in domestic, commercial, and industrial applications. The main functions include:
Verification and Calibration of Water Meters
Testing and certifying water meters to ensure they meet accuracy standards.
Calibration to legal metrology requirements before deployment in utility services.
Legal Compliance and Consumer Protection
Ensuring that water meters conform to the Legal Metrology Act, 2009, and applicable Bureau of Indian Standards (BIS) specifications.
Preventing overcharging or undercharging of water usage for consumers and businesses.
Standardization of Measurement
Establishing a uniform standard for water flow measurement across different meter manufacturers.
Ensuring that meters comply with national and international metrological guidelines.
Periodic Reverification and Inspection
Testing and recalibrating meters in service to detect any measurement drifts.
Ensuring long-term reliability and durability of water meters in different environmental conditions.
Support for Water Utilities and Municipal Corporations
Assisting water supply authorities in adopting accurate and efficient billing systems.
Reducing revenue losses caused by faulty or tampered water meters.
Example Applications
Water meter testing has applications across various sectors, ensuring that water measurement is both accurate and legally compliant. Some of the key applications include:
Domestic Water Supply (Household Applications)
Verification of residential water meters used in apartment complexes, gated communities, and individual houses.
Preventing overbilling or underbilling by water supply boards.
Commercial and Industrial Use
Testing of large-scale water meters used in factories, hotels, hospitals, and office buildings.
Municipal and Government Water Distribution
Calibration of municipal water meters to track large-scale water distribution.
Helping local government authorities detect leaks, wastage, and unauthorized water usage.
Irrigation and Agriculture
Verification of flow meters used in irrigation systems to regulate and optimize water usage.
Preventing misallocation of water resources in agricultural projects.
Fire Protection and Emergency Services
Ensuring fire hydrant flow meters accurately measure water flow for firefighting and emergency responses.
Traceability
Traceability in water meter testing ensures that all measurements taken by the testing laboratory are linked to internationally recognized standards. This is crucial for legal metrology, trade, and scientific applications.Traceability in Water Meter Testing at CLLM, Kakkanad includes:
The Water Meter Testing Lab at CLLM maintains secondary flow standards, calibrated against standards at NABL Accredited Fluid Control Research Institute (FCRI), Palakkad.FCRI provides traceable calibration services to industries by linking its standards to national and international standards like those maintained by NPL (India) and BIPM (France). These secondary standards are used to verify the accuracy of working standard water meters.
(6) Sphygmomanometer Lab (Central Laboratory, Kakkanad, Ernakulam)
Functions in Industry
The Sphygmomanometer Lab at the Central Laboratory of Legal Metrology (CLLM), Kakkanad, Ernakulam, is responsible for calibrating, verifying, and certifying blood pressure measuring instruments (sphygmomanometers) used in medical and healthcare settings. Given that blood pressure measurement is crucial for diagnosing hypertension, heart disease, and other medical conditions, maintaining accuracy in sphygmomanometers is essential for patient safety and medical reliability. Key Functions of the Sphygmomanometer Lab are:
Calibration and Verification of Sphygmomanometers
Ensures that both digital and manual BP monitors provide accurate readings.
Conducts testing against high-precision reference pressure standards.
Regulatory Compliance and Standardization
Ensures that BP monitors comply with the Legal Metrology Act, 2009 and relevant healthcare guidelines.
Certifies sphygmomanometers based on Bureau of Indian Standards (BIS) IS 7654:1975 and ISO 81060-1/2.
Periodic Recalibration and Quality Control
Detects measurement drift or inaccuracies that could lead to incorrect diagnoses.
Ensures consistent accuracy in medical devices over time.
Support for Healthcare and Medical Device Industry
Assists hospitals, diagnostic centers, and medical practitioners in maintaining accurate BP measuring instruments.
Supports medical device manufacturers in verifying new sphygmomanometers before market distribution.
Consumer Protection and Legal Metrology Enforcement
Ensures that home-use BP monitors meet regulatory standards, protecting consumers from faulty or unreliable devices.
Conducts random inspections and audits to prevent the sale of substandard medical devices.
Example Applications
Sphygmomanometer calibration and verification are critical in various healthcare and industry applications to ensure accurate diagnosis and treatment.
Hospitals and Healthcare Facilities
Calibration of sphygmomanometers used in ICUs, emergency rooms, and outpatient clinics to ensure precise blood pressure readings.
Verification of BP monitors in cardiology and nephrology departments, where accurate blood pressure monitoring is critical.
Clinics and Diagnostic Centers
Ensuring that blood pressure devices used by general practitioners provide accurate readings for effective patient care.
Preventing incorrect hypertension diagnoses due to faulty BP monitors.
Home Healthcare and Personal Medical Devices
Certifying digital BP monitors used by individuals for self-monitoring.
Ensuring that portable BP measuring devices meet the required accuracy standards before being sold in pharmacies and online.
Medical Device Manufacturing and Quality Control
Assisting medical equipment manufacturers in testing new BP monitors before they are released to the market.
Ensuring compliance with international accuracy standards (ISO, BIS, WHO guidelines).
Government Health Programs and Research
Verifying BP monitoring devices used in public health screenings and rural health programs.
Assisting in research projects where blood pressure data is critical for epidemiological studies.
Traceability
Traceability in sphygmomanometer calibration ensures that all blood pressure measurements are linked to internationally recognized standards, ensuring accuracy in medical diagnostics.The Sphygmomanometer Lab at CLLM maintains secondary pressure standards, calibrated against standards at NABL Accredited Fluid Control Research Center (FCRI), Palakkad.These secondary standards are used to verify working standard sphygmomanometers.
Calibration Process for Sphygmomanometers:
Step 1: The sphygmomanometer is placed in a controlled pressure testing environment.
Step 2: The device is compared against a high-precision pressure reference under different simulated blood pressure conditions.
Step 3: Any deviation from the standard pressure reading is recorded.
Step 4: If necessary, the sphygmomanometer is adjusted to bring it within the acceptable error margin.
Step 5: A Calibration Certificate is issued, confirming that the device meets the legal and medical accuracy requirements.
Step 6: The device is either approved for medical use or rejected if it does not meet the accuracy criteria.
Recalibration Periodicity
Sphygmomanometers must be recalibrated at least once every year to ensure continued accuracy and regulatory compliance.
(7) Clinical Thermometer Lab (Central Laboratory, Kakkanad, Ernakulam)
Functions in Industry
The Clinical Thermometer Lab at the Central Laboratory of Legal Metrology (CLLM), Kakkanad, Ernakulam, is responsible for calibrating, verifying, and certifying clinical thermometers used in healthcare and medical applications. Accurate temperature measurement is critical for diagnosing fever, infections, and other medical conditions, making precise thermometer calibration essential for patient safety and public health.
The lab ensures that both digital and mercury-based clinical thermometers provide accurate readings by testing them against high-precision temperature reference standards. It ensures compliance with the Legal Metrology Act, 2009, and relevant healthcare guidelines. Certification of thermometers is done based on the Bureau of Indian Standards (BIS) IS 3055 and ISO 80601-2-56, ensuring standardization across all medical devices.
The lab conducts periodic recalibration to detect measurement drift and inaccuracies, ensuring that clinical thermometers maintain consistent accuracy over time. By supporting hospitals, diagnostic centers, and medical device manufacturers, the lab ensures that all clinical thermometers meet the required medical and legal standards before they are used in patient care.
Consumer protection is another key function of the lab, as it prevents the sale of faulty or substandard thermometers. The lab performs random inspections and audits to ensure that thermometers meet regulatory requirements before being distributed in the market.
Example Applications
The calibration and verification of clinical thermometers are crucial in various healthcare and industry applications to ensure accurate medical diagnoses and treatment.
In hospitals and healthcare facilities, clinical thermometers are used in ICUs, emergency rooms, and patient wards to monitor body temperature accurately. Pediatric and geriatric departments also rely on highly precise thermometers to detect fevers in vulnerable patients.
Clinics and diagnostic centers use oral, rectal, and infrared thermometers to diagnose infections and fevers. Ensuring the accuracy of these devices helps prevent misdiagnosis and incorrect treatments.
Home healthcare and self-monitoring devices, such as digital thermometers used by individuals, must be verified and certified before being sold in pharmacies or online stores. This ensures that consumers can trust the accuracy of their thermometers when monitoring health conditions at home.
Medical device manufacturers conduct quality control checks on new thermometer models before releasing them into the market. Compliance with ISO and BIS accuracy standards ensures that medical thermometers are safe, reliable, and effective for clinical use.
Government health programs and research initiatives rely on accurate temperature measurement for epidemiological studies, fever screening during disease outbreaks, and public health monitoring. Large-scale health screenings, such as those conducted during pandemics, require thermometers that meet strict accuracy standards.
Traceability
Traceability in clinical thermometer calibration ensures that all temperature measurements are linked to national and international standards, maintaining accuracy for medical diagnostics.
The Primary Temperature Standards are maintained at the National Physical Laboratory (NPL), India, ensuring traceability to SI units for temperature measurement (Kelvin, °Celsius, °Fahrenheit).
At CLLM, Kakkanad, secondary temperature standards are calibrated against standards at NABL Accredited Fluid Control Research Center (FCRI), Palakkad, maintaining a traceable chain of accuracy. These secondary standards are then used to verify working standard clinical thermometers, which are subsequently used by Legal Metrology Inspector Offices to ensure that thermometers in hospitals, clinics, and pharmacies meet required accuracy levels.
Calibration Process for Clinical Thermometers:
A clinical thermometer is tested in a temperature-controlled water bath. The thermometer’s reading is compared to a high-precision temperature reference under different controlled temperature conditions. Any deviation from the reference standard is recorded. If necessary, the thermometer is adjusted to bring it within the acceptable error margin. Once the device meets legal and medical accuracy requirements, a Calibration Certificate is issued. If the device fails to meet the required standards, it is rejected.
Thermometers must be recalibrated at least once every year to ensure ongoing accuracy and compliance with medical and metrology regulations.
(8) Gold Testing Lab (Central Laboratory, Kakkanad, Ernakulam)
Functions in Industry
The Gold Assaying and Testing Laboratory (GATL)at the Central Laboratory of Legal Metrology (CLLM), Kakkanad, Ernakulam, is a pioneering government-owned gold testing lab in India, established to ensure consumer protection, fair trade, and transparency in the gold and precious metals industry.
GATL ensures accurate testing of gold and precious metals, continuously adopting advanced assaying techniques to meet industry needs. It prioritizes precision, reliability, and compliance with BIS standards, safeguarding consumer interests.
Key Functions of GATL:
The laboratory was established in 2003 following a directive from the Hon. High Court of Kerala (O.P. No. 21051/1997) and was conceptualized by the Centre for Earth Science Studies (CESS), Trivandrum. It was set up to ensure both quality and quantity compliance in gold bullion transactions.
Currently, the Government of Kerala is upgrading GATL to function as an “appropriate laboratory” under the Consumer Protection Act, 1986, reinforcing its role as a regulatory authority for gold purity testing.
Example Applications
Gold testing is vital for authenticity, transparency, and legal compliance in financial and commercial transactions.
Jewelry & Bullion Trade: Certifies gold purity, preventing fraud and ensuring BIS hallmarking compliance.
Banks & Financial Institutions: Verifies pledged gold for loans, ensuring accurate valuation.
Refineries & Hallmarking Centers: Assesses raw gold purity before refining and hallmarking.
Export & Import Trade: Issues gold purity certificates for international compliance.
Government & Law Enforcement: Detects adulteration with toxic metals like cadmium and palladium, protecting consumers and ensuring fair trade.
GATL plays a critical role in preventing unfair practices by ensuring gold remains free from harmful adulteration and meets safety standards.
Traceability
Traceability in gold assaying ensures that gold purity measurements remain accurate, standardized, and legally valid, maintaining trust in gold transactions.
The Gold Assaying and Testing Laboratory (GATL) at CLLM, Kakkanad, follows strict metrological standards to ensure that its test results are traceable to national and international standards.
Gold Testing and Certification Process at GATL:
The Bureau of Indian Standards (BIS) has established guidelines for gold fineness and marking under IS 1417 and IS 1418. These standards ensure the accuracy and reliability of gold purity testing across India. The Gold Assaying and Testing Laboratory (GATL) in Kakkanad follows these BIS standards to assess gold purity using the cupellation (fire assay) method.
The assaying process applies to various types of gold alloys, including:
Yellow Gold (916 parts per thousand or 22K)
White Gold with Nickel or Palladium
Gold Alloys with over 40% Silver
High-Purity Gold (999% fineness)
Various steps followed by the GATL in the assaying of yellow gold are shown below:
1. Sampling Methods
To ensure reliable testing, samples are collected from gold bullion and jewelry using the following techniques:
(a) Cutting Method
Samples are cut from diagonally opposite corners of the bar using a sharp steel chisel.
Each sample weighs 1g to 1.5g and is flattened, rolled, and mixed before further testing.
(b) Drilling Method
Used for gold ingots, drilling is done at top and bottom corners using a 3 to 10 mm high-speed steel drill.
If the ingot is non-uniform or of low fineness, at least 4 drillings (2 from the top, 2 from the bottom) are taken.
Surface drillings from the first revolutions of the drill are discarded.
The minimum weight of drillings must be 5g for accurate results.
(c) Dip Sampling
When bullion or jewelry is melted, a preheated graphite stirrer is used to mix the molten metal.
A 5g dip sample is taken from the center of the molten metal just before casting.
The sample is either granulated, cast into a button, or solidified for further analysis.
Quartz tubes can also be used for dip sampling.
2. Preliminary Assay & Analysis
If the composition of the gold alloy is unknown, a Preliminary Assay using XRF
Spectrometry is conducted before proceeding with detailed analysis.
Analysis Sample Preparation
Two samples of the alloy (weighing 125mg to 250mg) are transferred into assay-grade lead foil.
The mass of foil (or foil + beads) must be at least 4g for samples up to 200mg and 6g for samples from 201mg to 300mg.
Pure silver (2.3 to 3 times the gold mass) is added for inquartation before further processing.
Proof Assay Samples
At least two proof assay samples are weighed with proof gold and pure silver.
The content of base metals is adjusted using copper for accuracy.
Both proof and assay samples are processed under identical conditions.
3. Cupellation and Precious Metal Button Treatment
Assay and proof assay samples are wrapped in lead foil and placed in magnesium oxide cupels.
The cupellation furnace is preheated to 1100°C, and samples are processed at 1050°C – 1100°C for about 25 minutes under oxidizing conditions.
The resulting gold-silver beads (buttons) are:
Cooled and cleaned with an assay brush.
Flattened with a polished hammer and rolled into thin strips (0.12 to 0.15mm).
Annealed and rolled into cornets for further testing.
4. Parting of Silver/Gold Samples
The cornets are immersed in parting acid (20ml nitric acid) and boiled for 15 minutes.
A second acid treatment (Parting Acid 2) is performed, followed by thorough washing.
The gold cornet is transferred to a porous parting cup, dried, and annealed at 700°C – 750°C.
The final gold sample is weighed to determine the purity.
Safety Note:
All parting operations with nitric acid must be performed under a fume hood, ensuring a safe working environment.
5. Proof Assays & Calculation of Results
Proof assay samples undergo identical testing conditions as assay samples.
At least two proof samples must be included per assay batch.
Calculation of Gold Content (W ‰ by Mass)
W=((m_2+Δm_1)/m_1 )×1000
Where:
m₁ = Mass of sample (mg)
m₂ = Mass of cornet (mg)
Δ = Average proof assay correction factor
6. Repeatability & Quality Standards
To ensure accuracy, duplicate determinations must not exceed the following deviations:
Yellow & Red Gold: ±0.5 parts per thousand (‰)
White Gold: ±1.0 parts per thousand (‰)
High-Purity Gold (990‰ or higher): ±0.2 parts per thousand (‰)
If results exceed these tolerances, the assay must be repeated.
For fine gold content (990‰ or more), proof sample values must not differ by more than 0.04mg. If the difference is greater, re-assaying is required.
Reagents and Equipment Used in Gold Assaying
Reagents:
Borax – Used as a flux to assist in melting.
Check Gold (999.9 ppt) – A reference gold sample free from lead and other impurities.
Copper, Lead, Nickel, Palladium, Silver – Used in the refining process.
Parting Acids: Dilute nitric acid solutions (1.2 g/ml & 1.3 g/ml) for silver removal.
Distilled Water – Ensures purity in chemical processes.
Essential Equipment:
High-Precision Assay Balance – Readability of 0.002 mg (for gold up to 990 fineness) and 0.001 mg (for 999 fineness).
Cupellation Furnace – Maintains a stable oxidizing atmosphere at 1150°C.
Cupels (Bone-Ash or Magnesia) – Absorb lead and other base metals.
Hammer & Anvil, Rolling Mills – Used for sample preparation.
Parting Flask, Platinum Basket & Parting Tray – Used for acid treatment.
Balling Pliers, Assay Cleaning Brush – For handling samples during testing.
Gold purity testing must be conducted periodically, especially before transactions, hallmarking, or export-import activities, to ensure compliance with legal metrology regulations.
(9) One Ton Lab for Testing High-Capacity Weights (Central Laboratory, Kakkanad, Ernakulam)
Functions in Industry
The One Ton Lab at CLLM, Kakkanad, specializes in testing, calibrating, and certifying high-capacity weights (up to one ton) used in industrial, commercial, and legal metrology applications. Accurate weight measurement is crucial for fair trade, regulatory compliance, and industrial precision, ensuring that large-scale weighing systems remain reliable and traceable.
Key Functions:
Calibration of high-capacity weights used in heavy industries, logistics, and manufacturing.
Verification of industrial weighing systems, ensuring compliance with legal metrology regulations.
Ensuring accuracy in bulk trade transactions, including agriculture, mining, and shipping.
Supporting quality control in industries that require precise weight measurements.
Example Applications
The One Ton Lab plays a critical role in various sectors where accurate large-scale weight measurement is essential.
Heavy Industries & Manufacturing: Ensures precision in raw material weighing for steel, cement, and automobile industries.
Agriculture & Bulk Trade: Verifies weighbridges used for grain, fertilizers, and bulk commodities.
Logistics & Warehousing: Certifies weight accuracy in cargo and freight handling.
Mining & Construction: Ensures correct weight measurements for minerals, sand, and building materials.
Government & Legal Metrology Enforcement: Prevents unfair trade practices by verifying industrial-scale weighing instruments.
Traceability
The One Ton Lab at CLLM, Kakkanad, maintains strict traceability to Fluid Control Research Institute, Palakkad, ensuring that high-capacity weights meet regulatory and industry-specific requirements.
Calibration Process:
Step 1: High-capacity weight samples are tested in a controlled environment at CLLM.
Step 2: The weights are compared against a certified reference weight for accuracy.
Step 3: Deviations are recorded, and necessary adjustments are made.
Step 4: A Calibration Certificate is issued, ensuring compliance with metrology standards.
Step 5: Recalibration is required annually to maintain accuracy and regulatory approval.
Global Impact
International Cooperation
Metrology plays a crucial role in harmonizing global trade, ensuring regulatory compliance, and fostering international cooperation. Countries collaborate through organizations such as the International Bureau of Weights and Measures (BIPM), International Organization for Standardization (ISO), and International Legal Metrology Organization (OIML) to establish uniform measurement standards.
Trade Facilitation: Standardized measurements reduce technical barriers in international trade, ensuring product compatibility across countries.
Mutual Recognition Agreements (MRAs): Countries accept each other’s calibration and testing standards, simplifying import/export procedures.
Global Health & Safety: Cooperation ensures uniform medical device calibration (e.g., sphygmomanometers, thermometers), contributing to global healthcare standardization.
Climate & Environmental Monitoring: International agreements rely on precise measurements for climate change research, pollution control, and resource management.
Role in Technological Advancement
Metrology drives technological innovation and industrial growth by ensuring precision, reliability, and interoperability in modern technologies.
Manufacturing & Automation: Precision metrology enables the production of high-tech devices, from semiconductors to aerospace components.
Artificial Intelligence & Robotics: Advanced sensors require calibrated measurements for autonomous systems, robotics, and AI applications.
Telecommunications & Data Networks: Accurate frequency measurements support 5G, satellite communication, and quantum computing.
Medical Advancements: Precise calibration of MRI scanners, radiation therapy equipment, and biomedical instruments enhances healthcare efficiency.
Impact on Science and Research
Metrology underpins scientific discovery and research breakthroughs by ensuring accurate, repeatable, and internationally accepted measurements.
Fundamental Physics & Space Exploration: High-precision measurements enable research in quantum mechanics, astrophysics, and cosmology (e.g., gravitational wave detection).
Pharmaceutical & Biotech Research: Metrology supports drug formulation, genetic sequencing, and vaccine development through precise chemical and biological measurements.
Energy & Sustainability Research: Standardized measurements improve renewable energy efficiency, nuclear safety, and carbon footprint assessments.
Material Science & Nanotechnology: Research in new materials, nano-scale engineering, and superconductors depends on high-precision measurement techniques.