To determine if a hot runner insulation testing tool needs calibration, five clear signals should be considered: calibration period expired, functional verification failed, instrument physical damage, abnormal fluctuations in measurement data, and imminent use in a critical mission. Among these, functional verification is the core method for rapid on-site screening, while periodic calibration is the minimum requirement for compliance.
I. Five Calibration Trigger Signals (Authoritative Basis)
Signal Judgment Method | Authoritative Basis
1. Calibration Cycle Overdue: More than 12 months past the last calibration date. JJF 2225-2025 explicitly recommends a "recalibration cycle of generally one year"; IEC 61557-8:2015 recommends annual calibration to ensure measurement traceability.
2. Functional Verification Failure: Using a standard resistor (e.g., 10 MΩ), the reading deviation is > ±5% or "OL" or "Err" is displayed. Fluke, Keysight, and other manufacturers' manuals mandate that "open circuit ∞, short circuit 0" verification must be completed before each use; any abnormality requires immediate discontinuation.
3. Instrument Suffers Physical Damage: Drop, water ingress, broken casing, damaged test lead insulation, oxidation of connectors. GB/T 25296-2022 requires testing equipment to be "kept in good condition"; Rotronic... Precision instrument manufacturers have clarified that recalibration is mandatory after physical impact.
4. Abnormal fluctuations in measurement data: If three consecutive measurements of the same hot runner system show fluctuations exceeding 30% (e.g., 45MΩ → 12MΩ → 58MΩ), excluding changes in the measured object, DL/T 976-2017 states that abnormal drift in insulation resistance values should be considered an "equipment failure warning," requiring immediate verification of instrument accuracy.
5. Before critical tasks: Used for scenarios such as new mold acceptance, customer review, safety certification, and export testing. CNAS requires that all equipment used to issue legally valid data must be within its valid calibration period, without exception.
Core conclusion: Functional verification failure = must be immediately stopped; Expired cycle = must be sent for calibration; Both combined = strictly prohibited from use.
II. On-site rapid judgment process (functional verification method)
Prepare standard resistors: Select 1 MΩ, 10 MΩ, and 100 MΩ standard resistors with an accuracy of ±1% and stable resistance values, and store them in a dry, insulated box.
Perform Open Circuit and Short Circuit Tests
Open Circuit Test: With L and E terminals floating, apply 500 V DC. The reading should be "∞" (or the instrument's maximum range).
Short Circuit Test: Directly short-circuit L and E terminals. The reading should be "0" or close to 0 Ω.
Both pass → Basic instrument functions normally.
Failure of either test → Immediately stop use and send for calibration.
Perform Standard Resistance Verification
Connect a 10 MΩ standard resistor to L and E terminals.
Apply 500 V DC. After stabilization, the reading should be within the range of 9.5 MΩ ~ 10.5 MΩ.
Within the range → Can continue to be used (but does not replace formal calibration).
Outside the range → Must be sent for calibration.
III. Recommendations for Dynamic Adjustment of Calibration Cycle (Based on Usage Intensity)
|
Usage Scenarios |
Recommended Calibration Cycle |
Description |
|
Regular Use (1-2 times per week, clean environment) |
12 months |
Complies with national standards, balances cost and safety. |
|
High-Frequency Use (Daily use, workshop environment) |
6 months |
Continuous vibration, oil contamination, and temperature differences accelerate component aging. |
|
Harsh environments (high temperature >40℃, high humidity >80%, high dust levels) |
3-6 months |
Refer to Rotronic sensor calibration recommendations; environmental stress significantly shortens lifespan. |
|
Before critical tasks (e.g., customer factory audits, export inspections) |
Send for calibration 30 days in advance |
Ensure calibration certificates are valid to avoid audit failures. |
IV. Management Recommendations: Establish a "Calibration Trigger Response Mechanism."
Affix Calibration Labels: Affix "Calibration Date" and "Expiration Date" labels (waterproof stickers are recommended) to a prominent location on the instrument.
Digital Reminders: Set up "Calibration Reminders" using WeChat/DingTalk calendars for automatic push notifications 30 days in advance.
Record Anomalies: Record all functional verification results, abnormal readings, and damage in the "Insulation Testing Tool Usage Log."
Designate a Responsible Person: The equipment administrator should centrally manage calibration, verification, and archiving to avoid a vacuum of responsibility.
