Calibration is formally defined as a set of operations that, under specified conditions, show the relationship between the values reported by the measurement system with a reference base (standard). In general, device calibration is one of the most effective ways to track the accuracy and quality of measurements.


Purpose of calibration:

The purpose of calibration is to eliminate or reduce deviation and inaccuracy in the user’s measuring device, relative to the reference base. Calibration is very important wherever measurement is important, as it allows users to have confidence in the results they monitor, record and subsequently control.

There are many cases in which device and equipment calibration is critical, including: air separators and pure gas production, laboratories, refineries, petrochemicals, pharmaceuticals, food industries, etc.

The air separator and pure gas production industries have gas analyzers that require periodic calibration. During calibration, the analyzer is exposed to reference gases, which is the instrument’s response to the calibration gas as a measurement scale or reference point.

Calibration of gas analyzers consists of two steps. First “zero” and then “span” should be adjusted and calibrated.

First step: Zero Calibration

Zero calibration is a recommended procedure that should be performed periodically to improve the performance of the analyzers. This is especially important when the analyzers are operated outside of normal environmental conditions.

When performing a zero calibration, always use Zero Air calibration gas or a reference device (such as a calibrated portable device). “Zero” reading setting There is no clear standard that defines zero air. Many analytical methods, including some analyzer-specific methods such as EPA methods, are used to determine the zero point.

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Be sure to read: What are laboratory gases and what are the types of laboratory gases?

Second step: Span Calibration

The detector is exposed to the calibration gas and the calibration process is performed. The calibration accuracy level of the range is subject to external influences such as gas concentration ranges and airborne pollutants that may affect the calibration accuracy.

Selection of reference gas

The most important step for proper calibration of analytical instruments and safety monitors is the selection of the correct gas. There are some important preliminary steps before calibration. First, it is important that the expiration date of the gas has not expired. Second, the type and concentration of the gas must match what is required by the device manufacturer or the industrial standard. Third, tubes, regulators, and adapters must be compatible with the device to be calibrated. The purity of the gas can have a great effect on the result of the analysis, and the higher the purity of this reference gas, the more accurately the device is calibrated and, as a result, the analysis obtained is more accurate.

If repairs are necessary, expert technicians should look for the root cause to properly repair and service the device.

As a result, calibration may include a report or certificate that assures the end user that the device meets specifications. Ensure that the calibration laboratory is fully accredited in accordance with the requirements of “ISO/IEC 17025:2005” to perform the calibration.

ISO/IEC 17025:2005:

Specifies general requirements for qualification to perform tests and/or calibrations, including sampling. This includes testing and calibration performed using standard methods, and methods developed in the laboratory.

Conditions for calibrating measuring devices:
  • According to the device manufacturer’s recommendation
  • After any mechanical or electrical disturbance
  • periodically (yearly, seasonally, monthly)
Reasons for device calibration:
  1. Reduction of hidden costs
  2. long life of the device
  3. increasing safety
  4. Easier issuance of calibration certificate
Reduction of hidden costs: The hidden costs and risks associated with an uncalibrated measuring device can far exceed the cost of calibrating that device. Since the calibration of measuring devices avoids precision errors, it helps manufacturers to limit the mistakes that can occur during the production process that lead to poor quality products. Long life of the device: Every measuring device wears out over time. By calibrating the devices, it can be avoided to replace it with a new device. Finally, devices can be used for a longer period of time. Increasing safety: Because calibration increases safety, many industries use calibration to protect their equipment and employees. Safety is also important when calibrating measuring devices. Because the slightest mistake can lead to damage to the device and also damage to the employees.
Easier to issue a calibration certificate:

Many industries are required to have the relevant calibration certificate for their legal activity.

that if the equipment and devices are regularly calibrated. The certificate can be easily obtained from the relevant regulatory bodies.

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