HI,

I looking for ways to calculate uncertainty after a material measurement with 85070E. Any such calculator? If no, what is the way to calculate it? Please advise

I looking for ways to calculate uncertainty after a material measurement with 85070E. Any such calculator? If no, what is the way to calculate it? Please advise

In the help file of 85070E there is information about the uncertainty and also some example of calculating the uncertainty.

I should mention also that performing a full error analysis of a dielectric measurement is not an easy task. What may be even more discouraging is that the error analysis is specific to the given measurement, which will include sample properties, frequency, network analyzer etc. For example the analysis made for 5 GHz will not apply for 500 MHz even though we have the same sample and nothing else did change besides the frequency.

I will divide the error sources in the following categories:

â€¢ Accuracy of the network analyzer (we measure the reflection with a limited accuracy and then use it to calculate the permittivity)

â€¢ Accuracy of the calibration (includes how good the short is and also knowledge of the water temperature and water to be distilled and deionized). Most of this may be considered as operator error.

â€¢ Accuracy of the probe model that is used for calculation.

â€¢ Operator errors. This includes, but is not limited to having air gap between the probe and the sample (for solid sample) or air bubbles for liquid; touching the cable after calibration; calibration errors as mentioned above etc.

An alternative method to estimate the uncertainty is to measure very well known material. In the case of the dielectric probe 85070E the best is to use some of known liquids, such as methanol or isopropyl alcohol. NPL (National Physics Lab at UK) has tabulated data for some liquids in their CETM 33 document by Andrew Gregory and Bob Clarke. You can download it from the NPL web-site, free of charge. Just enter website http://libsvr.npl.co.uk/npl_web/search.htm and type 'CETM 33' in the box marked 'NPL Report Number'.

Stoyan Ganchev