ASL F25 circuits

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The F25 and F250 (a later version) are 10ppm resistance bridges for thermometry. Operating at 375Hz they are less tolerant of long cables (no quadrature balance). The higher frequency also permitted  a smaller ratio transformer.
Edit: Oops, sorry for the first item. It was the contents of the collection of monographs referred to in the footnotes. They can be accessed via the link: -

https://drive.google.com/folderview?id=1TbomXeoBbIe-IVADaOOmyyLH9le-3wAt