It is better to judge whether calibration is required from the calibration requirements:
1. For safety and health, the manufacturer will clearly explain or inform, otherwise, it generally doesn't belong to this category.

2. Verification of products, including direct judgment, such as: calipers, multimeters. Product testing support, such as: DC power supply, constant temperature bath, because some products need to be tested in certain specific environments, this must be calibrated.

3. Test type, this kind also needs to be calibrated.

4. Those that affect product processing are generally the instruments on the production equipment. Many people can’t tell them apart. Simply put, those that directly affect the product processing results need to be calibrated. It can be distinguished in this way. The work instruction clearly specifies that the parameter adjustment needs to be calibrated. Temperature, rotational speed, air pressure. If it isn't listed in the work instruction, it only appears in the equipment inspection, such as: oil pressure, water pressure, air pressure, etc. This is only for monitoring the operating environment of the equipment, and generally doesn't need to be calibrated. 

The oil pressure gauge should be an instrument that monitors the operating environment of the equipment, and it doesn't need to be calibrated. The main functions of this gauge are:

1. During normal inspection, the oil pressure of the equipment is normal and quick inspection.

2. The equipment quickly eliminate oil pressure problems in case of failure. The purpose of calibration is mainly to confirm the accuracy and precision of the instrument. Even if this kind of meter is unqualified, as long as the equipment can still operate well, it will not affect the product quality, this kind of meter, during the annual maintenance, it is enough for the equipment engineer to check. Of course, if abnormalities are found during regular spot checks, it is necessary to immediately report back and replace them.