18.6.1 Do We Need to Measure Our Dielectric Materials at all?

Perhaps we can consult manufacturers' data sheets or consult the scientific literature. Either option can be adequate for the early design stages of the system development process, but for end-use applications it is usually advisable to measure (or have measured) the materials that are being used. There are a number of reasons for this. For example, the dielectric properties of all ceramics depend critically on how they are prepared and sintered, so there is no such thing as a 'standard' or 'representative' batch of sintered alumina. Likewise, apolymeric material like 'PVC' is far from being a uniquely defined substance - polyvinyl chloride is prepared in many different ways, having different amounts of plasticiser and other additives admixed with it. Both the additives and the processing of the polymer give rise to a whole range of different 'PVC polymers with varying dielectric properties, so the uncritical adoption of data on 'PVC from a database will not do. Usually, if we have a 'one-off job, unless we already have a suitable measurement system available, it will be most cost-effective to ask a test house or calibration lab to perform measurements for us. If we have a long-term interest in measuring or testing dielectric materials we may well decide to set up a measurement system ourselves, but even in...