The accuracy and reliability of your test instrument is essential and requires verifying at regular intervals via calibration. Electrical testing is an environment where high precision is required and there are a number of factors which can affect this. Even the very best quality test instruments can start to drift in accuracy over time, which could be due to age, use, environmental factors or physical damage. So it is essential that you start and maintain a proper calibration schedule.
What is calibration and when should I do it?
Calibration is the process through which you compare the readings of a test instrument against standard references that have a known degree of accuracy, and which are traceable to applicable standards. The idea of calibration is to ensure that these readings are within acceptable tolerance limits and therefore you can confirm that the instrument is accurate, reliable and compliant with these applicable standards.
If an instrument is not calibrated it may start to provide incorrect readings, which can lead to the wrong diagnosis of an electrical problem or the wrong type of installation, and this can lead to potentially damaging safety hazards. The frequency of calibration would normally be based on an assessment of factors such as frequency of use, the critical nature of the work, the type of environment you are working in and the regulatory controls you are working to. So an instrument would be calibrated more frequently if:
- You use the instrument every day
- You use the instrument for safety critical work at high voltages
- You use the instrument in difficult environments which include dust, heat or moisture
- You are bound by strict regulatory controls
Signs that your test instrument needs calibrating
So this should allow you to design a strong and robust calibration schedule, but if you don’t have this in place, what are the signs and indicators that your test instrument needs calibration?
- Inconsistent readings – If you regularly carry out the same tests in the same conditions, and your test instrument has started to provide erratic and inconsistent readings where they used to be very stable and predictable, this could indicate internal drift or a faulty internal component, and hence it might require calibration.
- Heavy usage – If the test instrument is used in very harsh environmental conditions, such as a construction site or in an industrial plant, this can accelerate the drift experienced in the instrument readings. Even if the instrument is quite a few years old this can start to occur. If you have previously relied on just an annual calibration, it would be recommended to make this more frequent.
- Incident – Where there has been an incident involving your test instrument, such as a current overload or a voltage spike, this can damage the internal circuits and start to affect the accuracy of the instrument. Even if you drop or damage the instrument this can also occur. Calibrating a test instrument after an incident such as this is recommended.
- Failed test – Sometimes we use a standard reference source to test the instrument during the normal course of our testing duties. For example, a multimeter can be tested against a standard voltage supply. If the results you are achieving from your multimeter don’t match these known standard reference sources, it is an indication that the instrument needs calibration.
- External requirements – In some industries there are external requirements to have instruments calibrated to specific standards at specific intervals, and before certain work is undertaken. This could be when working on a project or prior to an audit, and is a clear indicator that a calibration needs to be scheduled.
At Test Instrument Solutions we have a full calibration service where we can calibrate your test instruments to keep you fully compliant with your regulatory requirements.
Please note that this section is for information purposes only. Anyone using equipment referred to in this section must be suitably qualified and/or experienced within the respective field. If in doubt before use, please consult a qualified electrician or engineer & thoroughly read all instruction booklets.