The Instrument Testing and Calibration Center provides on-site inspection and measurement services

The Instrument Testing and Calibration Center provides on-site inspection and measurement services

Calibration Procedure for Network Testers

1、 Purpose

Ensure the accuracy and reliability of the measurement results of the network tester to meet relevant standards and practical usage requirements.

2、 Scope of application

Applicable for calibration work of network testers within the specific model range.

3、 Reference standards

[List referenced calibration specifications, industry standards, etc., such as JJF 1534-2015 "Calibration Specification for Data Network Performance Testers", IEEE related standards, etc.]

4、 Calibration environmental conditions

1. Temperature: (20 ± 5) ℃, with a temperature change rate not exceeding 1 ℃ per hour. To avoid measurement errors caused by significant temperature fluctuations during the calibration process that may affect the performance of the internal electronic components of the tester.

2. Relative humidity: 35% -75%. Prevent excessive humidity from causing condensation inside the instrument and corroding the circuit; Low humidity may cause static interference to the test results.

3. Power supply conditions: voltage (220 ± 10) V, frequency (50 ± 1) Hz. A stable power supply is the basis for ensuring the stable operation of the tester, and voltage fluctuations and frequency deviations can affect the measurement accuracy of the tester.

4. Electromagnetic environment: Keep away from strong electromagnetic interference sources such as large motors and transformers, and the surrounding magnetic field strength should not exceed [specific magnetic field strength value]. Strong electromagnetic interference may penetrate the test signal, causing measurement results to deviate.

The Instrument Testing and Calibration Center provides on-site inspection and measurement services

5、 Calibration equipment

1. Standard delay generator: The accuracy should be better than one-third of the delay measurement accuracy of the network tester being calibrated, used to calibrate the delay parameters of the network tester. Provide accurate delay reference for the testing instrument when measuring network transmission delay.

2. Frequency counter: The frequency measurement error should not exceed one-third of the measurement error of the data packet transmission rate of the calibrated network tester, used to calibrate the data packet transmission rate of the tester. Used as a precise measurement tool when measuring the frequency of data transmission from ports.

3. Calibration Ethernet Cable: Compliant with relevant standards, with a characteristic impedance of (50 ± 2) Ω, ensuring stable signal transmission, used to connect testing instruments and calibration equipment.

4. Standard signal source: The accuracy of parameters such as frequency and amplitude of the output signal meets the calibration requirements, providing standard test signals for the tester.

6、 Preparation before calibration

1. Appearance inspection: Check whether the shell of the network tester is damaged or deformed, whether the display screen is damaged or abnormal, whether the buttons and knobs can operate normally, and whether the interfaces are loose, oxidized, etc. If the above problems exist, repair or replace the relevant components before calibration.

2. Preliminary functional inspection: Connect the power supply, turn on the network tester, check if it can start normally, whether each menu and function option can be called up normally, perform a simple self-test function, and preliminarily determine whether the instrument function is normal.

3. Preheating: Connect the network tester to the power supply and preheat for 30 minutes to reach a stable working state, reducing measurement errors caused by unstable instruments.

7、 Calibration items and methods

（1） Throughput calibration

1. Connection method: Use a calibration Ethernet cable to self loop connect the two ports of the network tester.

2. Parameter setting: Set different frame lengths on the network tester, such as 64 bytes, 128 bytes, 256 bytes, 512 bytes, 1024 bytes, 1280 bytes, 1518 bytes; Set the testing time to [X] seconds.

3. Measurement steps: Activate the throughput test function and record the throughput value displayed by the tester. Repeat the test 3 times for each frame length and take the average.

4. Result judgment: Compare the measured average throughput with the theoretical value, and the error should be within ± [X]%. The theoretical value is calculated based on the testing instrument port line rate and frame length using relevant formulas.

（2） Packet loss rate calibration

1. Connection and settings: connection method calibrated with the same throughput; Set the network tester to send a certain number of data packets at a fixed rate, with the number of packets set to [X] and the rate set to [X]% of the port line rate.

2. Test operation: Start the packet loss rate test, count the number of packets sent and received, and calculate the packet loss rate. Repeat the test three times.

3. Qualification judgment: The error between the measured packet loss rate and the theoretical packet loss rate (which should be 0) should be within ± [X]%.

（3） Delay calibration

1. Build a calibration link: Connect the standard delay generator and the network tester through a calibration Ethernet cable to form a loopback link.

2. Parameter setting: Set different fixed delay values on the standard delay generator, such as 10 μ s, 50 μ s, 100 μ s, and 500 μ s; Set up the network tester to send messages of a specific byte length, such as 1000 bytes.

3. Measurement process: The network tester sends a message, and the receiving end calculates the average delay of the message passing through the standard delay generator, records the delay value measured each time, and repeats the measurement 5 times for each delay setting.

4. Result evaluation: Compare the measured delay value with the delay value set by the standard delay generator, calculate the error, and the error should be within ± [X] μ s.

（4） Data packet sending rate calibration

1. Connect the instrument: Connect the Ethernet port of the network tester to the frame head trigger, and then connect the frame head trigger to the frequency counter.

2. Parameter setting: Set the port speed to 1Gbps on the network tester, send a 64 byte message, and set the sending time to [X] seconds.

3. Conduct testing: Activate the packet sending function, the frame header trigger detects the frame header in the Ethernet signal and generates a counting pulse. The frequency counter measures the sending frequency and records the value displayed by the frequency counter. Repeat the test 3 times.

4. Judgment criteria: Compare the measured packet transmission rate with the theoretical rate, and the error should be within ± [X] fps.

8、 Calibration result processing

1. Data recording: Carefully record the measurement data, testing conditions, and other information of each calibration item during the calibration process. The records should be clear, complete, and accurate, and should not be altered arbitrarily.

2. Certificate issuance: Based on the calibration data, if the measurement results of all calibration items meet the requirements, a calibration certificate should be issued. The calibration certificate should include information about the testing instrument, calibration items, calibration results, calibration date, calibration personnel, etc; If there are some items that do not meet the requirements, a calibration report shall be issued, clearly indicating the unqualified items and measurement results in the report.

3. Non conformance handling: For network testers that fail calibration, a stop use label should be posted to prevent misuse; Analyze the reasons for the nonconformity, and if it is an instrument malfunction, repair it and recalibrate it after repair; If it is caused by improper operation or other reasons, perform calibration again.

9、 Return time interval

The recommended interval for recalibration of network testers is 1 year. If abnormal measurement results are found during the use of the tester, or if higher precision requirements are required for the measurement results after maintenance, calibration should be carried out in a timely manner.