## Quality manual for calibration – Annex 10

### 1. General

In order to ensure that a calibration result complies with specifications or limit values, Nordtec Instrument AB applies a decision rule where we take into account the allowed deviation from the product specification together with the measurement uncertainty from our own method.

Customers have the possibility to specify a different deviation for their instrument than the one specified by the manufacturer. In this case, the measurement uncertainty of the method will be weighted towards this deviation instead of the manufacturer’s.

### 2. terms used in the decision rule

Concepts | Symbol | Explanation |
---|---|---|

Permitted deviation | What the specification from the customer or the manufacturer of the instrument says the instrument should do. | |

Nominal value | Value of the reference (after correction) | |

Measurement uncertainty method | Measurement uncertainty of the method for the current calibration | |

Current measurement value | X | Measured value of the calibration object |

Accepted value | The decision rule is applied with accepted value | |

Failed value | The decision rule is applied with a failed value | |

Uncertain value | The decision rule cannot be applied. The value is at the limit and the customer decides whether to accept it or not. |

### 3. mathematical explanation

Our decision rule is based on a mathematical calculation. To simplify the understanding of this, we choose to show our decision rule schematically instead of in long calculation formulas.

**Accepted measurement values**

We accept all calibrations where the measurement uncertainty of the method is more than 70% within the allowed deviation.

This means that all examples in Figure 1 are approved values and are marked in our certificates with the symbol .

**Failed measurements**

Failure occurs when the measurement uncertainty of the method is more than 70% outside the allowed deviation (in other words, the measurement uncertainty of the method is less than 30% inside the allowed deviation).

This means that in this case all examples in Figure 2 are failed and are marked in our certificates with the symbol .

**Metrics where decision rule cannot be applied**

We also have cases where the decision rule cannot be applied. Examples of these can be found in Figure 3. The measurement uncertainty of the method is greater than the permitted tolerance specified. Or the measurement uncertainty of the method is just outside with only 60% within the accepted value. For all these cases, Nordtec Instrument does not take any decisions itself. We contact the customer who can decide if they think the instrument needs to be adjusted or not. As we deal with a lot of customers who have different tolerances in their operations, we want to be in close contact with the customer to understand their needs.

These measured values are marked in the certificate with the symbol .