Inspection standards and methods for inspector scales, factory inspections, and certification services

1. Overview and Importance of Scale Inspection

As precision measuring instruments, the accuracy of scales is directly linked to fair trade practices and consumer rights. From electronic kitchen scales and electronic body scales to mechanical body scales, different types of scales require specific inspection standards and testing methods during the inspection process. This article systematically explains the inspection process, testing methods, and quality requirements for scales from a professional inspection perspective, providing practical reference for QC personnel.

2. Preparation before inspection and factory audit

1. Supplier qualification review

• Check the measuring instrument production license of the manufacturer

• Review of quality system certification (ISO9001, ISO13485, etc.)

• Verify product certification information (CE, RoHS, FCC, etc.)

2. Production environment assessment

• Check the cleanliness and temperature and humidity control of the production workshop

• Evaluate anti-static measures and calibration equipment management

• Review of raw material inspection and traceability system

3. Preparation of inspection equipment

• Calibration and certification verification of standard weights

• Confirm the status of measuring equipment such as multimeters and calipers

• Integrity check of test tools and fixtures

3. Working principle and classification of scales

1. Overview of Working Principle

When an object is placed on the scale pan, pressure is applied to the sensor, causing deformation and impedance changes, which in turn output a changing analog signal. This signal is processed by the amplification circuit, converted to a digital signal by an analog-to-digital converter, and then processed by the CPU for display.

2. Product Categories

• Electronic kitchen scale: high precision and diverse functions

• Electronic body scale: Frequent use, high durability requirements

• Mechanical body scale: simple structure, easy maintenance

3. Main components

1. Weight sensor 2) Amplifier circuit 3) Filter circuit 4) Analog-to-digital converter

2. CPU 6) Power supply circuit 7) Buttons 8) Housing

3. Mechanism 10) Weighing pan

IV. Packaging inspection standards and inspection requirements

1. Outer box inspection

• Check the outer box material, strength and printing quality

• Verify the integrity of shipping labels and warning signs

• Confirm the effectiveness of packaging protection measures

2. Color box/blister packaging inspection

• Check packaging material quality and structural design

• Verify product information and barcode accuracy

• Confirm the correctness of packaging assembly

3. Accessories and Documents Inspection

• Check the accuracy of the instructions and warranty card

• Verify that the types and quantities of accessories meet the requirements

• Confirm multi-language version consistency

5. Safety performance inspection

1. Machinery safety inspection

• Check edges and sharp points to avoid injuries

• Verify battery compartment safety and leak-proof design

• Test structural stability and anti-slip performance

2. Electrical safety inspection

• Check the battery installation polarity

• Verify insulation performance and protection level

• Testing the effectiveness of circuit protection devices

6. Appearance quality inspection

1. Product conformity confirmation

• Verify product consistency against samples and specifications

• Check the correctness and completeness of identification and labels

• Verify color, material and consistency with confirmation samples

2. Appearance defect inspection

• Check for surface defects such as scratches, dents, stains, etc.

• Verify assembly clearance and fit accuracy

• Test button feel and responsiveness

7. Mechanical structure inspection

1. Structural integrity check

• Use the manual tap test to check for internal foreign matter

• Verify the firmness of assembly of each component

• Check the screw tightening and anti-loosening measures

2. Horizontal stability test

• Use a feeler gauge to measure the flatness of the floor mats

• Testing stability on a glass platform

• Record the maximum shaking value and adjustment status

3. Battery compartment safety inspection

• Test the battery door opening and closing smoothly

• Check the effectiveness of the electrical insulation protective film

• Verify battery contact reliability

8. Functional performance testing and inspection standards

1. Basic functional testing

Power on/off test :

• Continuously switch on and off 3 times to verify functional stability

• Check the power-on self-test and reset functions

• Test the reliability of the automatic shutdown function

Accuracy test :

• Select three test points: 10%, 50%, and 90% of the maximum weight

• Kitchen scale accuracy requirement: ±0.5%

• Body scale accuracy requirement: ±1%

• Record test data and deviation values

2. Display function test

LCD display inspection :

• Test all stroke display integrity

• Check contrast and viewing angles

• Verify backlight uniformity (if applicable)

Unit conversion test :

• Test the accuracy of unit conversions such as Kg, Oz, and Lb

• Verify unit display correctness

• Check conversion response speed

3. Special function test

Tare function test (kitchen scale):

• Place a 1kg weight and press the reset button

• Verification shows zeroing accuracy

• Testing the additional weight shows correctness

Overweight indication test :

• Place overweight verification alarm function

• Check the correctness of the displayed prompts

• Test the alarm deactivation function

Mechanical zero test (mechanical scale):

• Test the smooth operation of the zero adjustment knob

• Verify the accuracy of pointer zeroing

• Check the automatic zero return function

IX. Performance Testing and Inspection Verification

1. Electrical performance test

Battery voltage test :

• Use a multimeter to measure the operating voltage

• Verify voltage indication accuracy

• Record test conditions and results

Standby current test :

• Connect a multimeter in series to measure the standby current

• Record power consumption data

• Verify low power design compliance

2. Metrology performance test

Low voltage alarm test :

• Verify the accuracy of the low voltage warning function

• Testing Alarm Threshold Compliance

• Check display consistency

Maximum weighing test :

• Verify that the maximum range meets specification requirements

• Test the over-range protection function

• Recording test results

Resolution Verification :

• Test the accuracy of the minimum display unit

• Verify that resolution meets specifications

• Check display stability

3. Repeatability test

Repeatable weighing error test :

• Test 3 times with 50% of your maximum weight

• Calculated repeatability error (≤ 1 resolution unit)

• Record test data and deviations

Single and double foot test (body scale):

• Test the consistency of single-foot and double-foot weighing

• Verify that the eccentric load error meets the requirements

• Record the maximum deviation value

10. Special test items

1. Environmental adaptability test

Temperature impact test :

• Test accuracy at different ambient temperatures

• Verify temperature compensation function

• Recording temperature drift data

Humidity impact test :

• Testing performance stability in a high humidity environment

• Check the effectiveness of moisture-proof measures

• Record humidity impact data

2. Durability test

Key life test :

• Press the button a specified number of times

• Check button function and feel changes

• Recording test results

Impact durability test :

• Simulate shock during transportation and use

• Test structural strength and precision stability

• Record performance change data

11. Inspection Records and Report Requirements

1. Inspection data records

• Record all test data in detail

• Attached test conditions, equipment and environment information

• Save test photo and video evidence

2. Preparation of inspection report

• Contains product information and inspection batch

• Record inspection standards and sampling plans

• Detailed description of non-conformities and suggestions for improvement

3. Quality traceability system

• Establish product quality traceability records

• Save inspection data and test reports

• Provide quality improvement suggestions

12. Classification and treatment of common defects

1. Packaging defects

• The outer box is poorly printed, damaged or deformed

• Color box wrinkles and debonding defects

• Accessories are missing or incorrectly installed

2. Appearance defects

• Surface scratches, dents, stains

• Dirty mirror surface, bubble defects

• Uneven assembly gap

3. Functional defects

• Accuracy is too poor, display is missing

• Key failure, unit conversion error

• Poor battery contact

4. Structural defects

• Screws not tightened, parts loose

• Uneven foot pads and poor stability

• The battery door does not open and close smoothly

13. Inspection precautions

1. Standard weight management

• Use certified standard weights

• Regular inspection and calibration

• Record weight usage history

2. Test environment control

• Controlling the temperature and humidity of the test site

• Avoid vibration and airflow

• Ensure the test platform is horizontal and stable

3. Sampling plan development

• Determine the sampling quantity according to the AQL standard

• Consider product risk and materiality

• Record sampling process and results

14. Summary

Scale inspection is a systematic quality assurance process that requires inspectors to possess professional knowledge and a rigorous approach. Through rigorous inspection procedures and scientific testing methods, we can ensure the accuracy and safety of scale products. We recommend that inspectors continuously learn new knowledge and promptly update inspection standards to improve the professionalism and effectiveness of their inspection work and provide consumers with accurate and reliable measurement products. At China Huibang Focus, we specialize in product inspection and quarantine, testing and certification, supplier background checks, audits, and factory inspections.