How to decide calibration frequency of laboratory instruments?

校准实验室仪器是一项基本活动，可以对您的结果的可靠性充满信心。确定和不确定的错误都会导致您的结果变化。通过良好的实验室实践和培训，可以在某种程度上控制不确定的错误。另一方面，可以通过定期校准用于分析的仪器来克服确定错误。

需要多久进行一次校准？

Any accredited laboratory needs to maintain a calibration schedule of equipment used by it.National Accreditation Boards for Calibration and Testing laboratories recommend calibration frequencies based on regulatory bodies guidelines. In India NABL has issued such guidelines in the new draft document 103http://www.nabl-india.org/index.php?option=com_content&view = article＆id = 148＆itemid = 71which arepresented here for reference purpose.

Type of Equipment/Instrument/ Calibration Item	Recommended Frequency of Calibration	中间检查	Remarks
平衡	Every years or on repair ;	（a）每个称重零检查 （b）一个月 - 一点点检查使用接近工作能力的校准重量 (c) 6个月——重复性检查上and lower ends of the scale using a calibrated weight	Reference weights to be used should be standard class F2 or better with established permissible errors.
权重	重量必须由认可的实验室进行外部校准，至少两年。	Six monthly temperature check around working range	Maintain parameters to an accuracy of within a range as stipulated in methods.
Temperature Controlled Enclosures/恒温控制设备作为烤箱，孵化器，老化，真空；;环境条件室；	Preferably from an accredited calibration laboratory.
温度控制的外壳高压釜，温度控制的水浴，家具	To be carried out based on usage
温度计（玻璃中的液体）	经认可的实验室校准。	Once a year Check at ice point or at points of use.	冰点。如果校准的不确定性五倍，则需要完全重新校准。
RRTD，PRT，带指示器的热电偶	每年，跨工作范围或经认可的校准实验室的使用点。
TIMING DEVICES 停止手表，时钟，	Every Year
Hygrometer	通过认可的校准实验室进行校准
Pressure Gauge	通过认可的校准实验室进行校准
体积实验室（瓶装，移液器和体积瓶）*	Internal calibration on receipt.		应该验证的是，公差是可接受的限制（A类和B类玻璃磨砂）
流动 Rota仪表	Initial and recalibration after two years from an accredited calibration laboratory	每年一次对抗标准的肥皂泡沫计
Dry Gas Meter	经认可的校准实验室三年后的初始和重新校准
Pitot tube	经认可的校准实验室三年后的初始和重新校准
Orifice Plate	Initial calibration from an accredited calibration laboratory
气体传感器	两年后的初始重新校准		Using standard gases.
UV-Visible / IR / FT-IR Spectrophotometer / Colorimeter	季度光度法 Absorbance and wavelength accuracy for the working range		Using CRM
原子吸收 Spectrophotometer	Performance check by f Cu CRM as per manufacturer’s instruction.	使用时，标准解决方案of specific element	通常对th性能检查完成e initial value checked at the time of installation.
Conductivity Meter	每年一次，使用CRM进行全范围校准	每月参考标准，一个点校准。如有必要，调整电池常数。 使用时，标准解决方案
Gas 色谱仪，GC-MS / HPLC / LC-MS	季度，系统 performance 包含： Resolution, 灵敏度， 可重复性， retention time and noise level	使用时，标准溶液 /混合物
pH计	每年一次，使用CRM进行全范围校准	使用前要使用工作标准进行检查。
微夹	每年一次内部校准

The document under section 5.5 classifies laboratory equipments in following categories:

• 不直接参与测量的一般服务工具，例如，热板，搅拌器等
• Volumetric instruments such as volumetric flasks,burettes, pipettes,etc
• 测量仪器，例如PHH仪表，温度计，光谱仪，色谱，电化学仪器等
• Physical standards such as weights, measuring scales, reference thermometers,etc

Calibration of general purpose instruments is not necessary as their contribution to measurements is not critical.

It is not necessary to re-calibrate length scales as the manufacturer guarantees the length against a standard with established traceability. It is only necessary to store such units within controlled conditions of temperature and humidity.

Volumetric glassware comes under different classes, namely, Class A and class B .Class A glassware is supplied with a calibration certificate and class B glassware is calibrated against class A glassware. Volumetric glassware if used within the temperature range 25°C +/- 2°C does not require frequent calibration.

Frequently used analytical instruments also require frequent calibration. The frequency of calibration will depend on usage. It is best to decide the intervals on the basis of in house standard operating procedure guidelines which in turn are based on equipment supplier recommendations.

In order to generate high level of confidence on your results calibration should be carried out even out of prescribed schedule when an instrument has undergone major repairs, is relocated or its capabilities are enhanced through addition of add-on accessories.