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What does permissible deviation mean and is it important to you?

Maria mäter med testo

Published 2025-02-04

What does permissible deviation mean and is it important to you?

What does permissible deviation mean

There is no measuring equipment that measures exactly right. All instruments and sensors give more or less accurate readings. A common concept in this context is permissible deviation. Do you know the permissible deviation of your meters? What does the term actually mean? And how important is it for your daily measurements? In this article, we will clarify this and give some basic advice on how to think about the choice of measuring equipment in terms of accuracy.

Allowable deviation = instrument accuracy

All manufacturers carry out extensive quality checks and tests on measuring equipment before it leaves the factory. One important aspect is the permissible deviation. It is a measure of how accurate a measurement you can expect from the instrument or sensor. Put another way, it is the manufacturer’s promise of how much the readings can deviate at most. This is often stated in terms of accuracy in the manufacturer’s technical specification for the measuring equipment. For example, if you measure 20 °C with a temperature gauge that has an accuracy of ±1.5, this means that the temperature value can be between 18.5 and 21.5 °C – which is fine in many cases.

How accurate measuring equipment do you need?

This may sound strange coming from a company selling measuring equipment, but… don’t be blinded by the accuracy value and avoid buying unnecessarily sophisticated instruments, data loggers and sensors. Most people can live with the knowledge that the measurement accuracy is within a certain margin of error. If you measure the indoor temperature, it often doesn’t matter much if the temperature shifts half a degree up or down (unless temperature measurement is an important part of saving energy costs).

However, in some activities and environments, the manufacturer’s data is too imprecise and insufficient. In the medical, food and manufacturing industries, varying levels of temperature and humidity are critical to maintaining smooth processes and high product quality. This, together with strict industry requirements, means that operators in these fields need to calibrate their instruments and sensors at regular intervals (usually once a year), to keep track of the accuracy of their measurements.

Interconnected measuring equipment affects accuracy

Please note that not only measuring instruments but also sensors and some accessories have different accuracy. And if measuring equipment is paired, it will affect the accuracy of your measurements. For example, let’s say you use a temperature gauge that has an accuracy of ±0.2°C and pair it with a sensor with an accuracy of ±0.5°C. By adding these values, you get a total accuracy of ±0.7°C on your measurements. If you also choose to connect an extension cable to your measuring equipment, you should check the accuracy of the cable and its impact on your measurement results.

The exception is digital sensors

The above is not true when using digital sensors. The measuring instrument used with a digital sensor will only have a display function and the accuracy of the instrument will not affect the measurement result. In other words, what you need to keep an eye on is the accuracy of the sensor.

Fixed accuracy for temperature sensors

Some sensors always have a specific accuracy. No matter how it is made or by whom. For example, type K Class 2 thermocouple sensors have a fixed value of ±2.5 °C.

Order calibration to find out more precisely

To really know how accurate your instruments and sensors are, you need to calibrate them. We offer accredited calibration of the most common measurement quantities both in our lab and at your site. In some cases, a calibration may show that your measuring equipment actually has a higher accuracy than the technical specification. Good information for those who want to ensure flawless production and high quality. Indispensable for you in a business that needs to be able to demonstrate calibrated measuring equipment to comply with standards and legal requirements.

When purchasing measuring equipment, you can choose between calibration at fixed measurement points or selecting your own points (these should be measurement points that are common and important in your business). We usually recommend the latter option as it is usually the most relevant.

Is there something you are wondering about or want to know more about?
Email Lab and Calibration Manager Maria Almestål and she will get back to you as soon as possible.
maria.almestal@nordtec.se

Contact persons

Mats Landin

CUSTOMER SERVICE & SALES

Maria Almestål

Responsibilities: Lab Manager Calibration

maria.almestal@nordtec.se
031-704 10 82
031-704 10 70


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