Microwave power flux density measurement requires a specialist professional instrument, accurately calibrated using equipment traceable to the UK National Standard.
There are a number of such instruments readily available for this safety critical task, a number of which have been approved for use by leading oven manufacturers.
While expensive and sophisticated instruments may be purchased for this purpose, which users may view as not cost effective, compared to the number of times a test may be carried out. However, there are relatively inexpensive instruments available with specifications to meet the needs of technicians who repair/maintain microwave ovens.
Following the increased use of microwave ovens in the UK, in the early 90’s, oven manufacturers promoted their safety to allay fears among the general public.
The manufacturers adopted a pro-active approach in the early 90’s as oven sales increased. They restricted the supply of service information, spare parts and technical support to companies / technicians having suitable instruments and an “in-date” calibration certificates, ensuring the use of suitable, calibrated instruments.
This approach has been relaxed, resulting in the appearance and use of inaccurate instruments.
The UK National Physical Laboratory (NPL) confirms the need for accuracy and calibration on page 2 of their publication “A guide to power flux density and field strength measurement” published in 2004. ISBN 0 904457 39 7
“Neither an exacting specification nor an accurate instrument is a substitute for a regular calibration routine, as without calibration at suitable intervals the instrument is unlikely to remain accurate or perform to its intended specification. Furthermore, where measurements are intended for RF hazard purposes, the integrity of the measurement is paramount to ensure the safety of public and personnel.”
The specifications to be considered when choosing a microwave leakage detector are listed below
- Dimensions and weight
- Power source and current consumption
- Incorporated 5cm spacer
- Calibration accuracy
- Response to step input
- RF Power range
- Overload capability
- Sensor type
- Display type and resolution
- Nominal operating frequency (Frequency at which calibrated)
- Calibration stability
The above indicates fitness-for-purpose of a given instrument. However, many of the later models now available offer additional benefits that may make the task of the user easier. These benefits usually come at an extra cost.
If we consider the above list, items 1 to 3 are self-explanatory and are not considered further. Please click an the item above, for more detailed information