How should an inaccurate commercial oven be calibrated?

Please verify the following points and require itemized written supplier responses:（commercial oven oven-calibration） Compare set and actual temperatures with a reliable thermometer, then inspect sensors, controllers and elements before professional calibration. Do not rely only on dial markings; verify temperature regularly for batch baking. Define capacity, accuracy, materials and operating environment before requesting quotes on a uniform basis. Request specification sheets, test reports, certificates, maintenance manuals and spare-part lists. During acceptance, verify appearance, dimensions, functions, safety protection and packaging, and keep test records. Do not compare unit price alone; include customization, freight, spare parts, after-sales support and downtime risk. Keep written records of inquiries, confirmations, FAT, acceptance and warranty commitments.