{"product_id":"vintage-1940s-f-darton-relative-humidity-meter-precision-hair-hygrometer","title":"Vintage 1940s F Darton Relative Humidity Meter \/ Precision Hair Hygrometer","description":"\u003ch1\u003eVintage 1940s F Darton Relative Humidity Meter \/ Precision Hair Hygrometer\u003c\/h1\u003e\n\u003cp\u003eThis is a very nice, small (13.5cm diameter), Vintage 1940s F Darton Relative Humidity Meter \/ Precision Hair Hygrometer in a chrome and black cast casing with a hook for wall hanging. \u003c\/p\u003e\n\u003cp\u003eIn pretty good working condition, with a few surface scuffs and scratches in the chrome and flecks of dirt \/ discolouration under the glass, commensurate with age and use. There is also some loss of black coating on the rear of the brass base.\u003c\/p\u003e\n\u003cp\u003eI am not sure how accurate it is at measuring % Relative Humidity, and I haven't tried to calibrate it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eApproximate Size:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eFace Diameter: 13.5 cm\u003c\/li\u003e\n\u003cli\u003eRear Diameter: 15 cm \/ 6\"\u003c\/li\u003e\n\u003cli\u003eDepth: 4.5cm\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe face and base are marked as follows:-\u003cbr\u003e\u003cbr\u003eRange 0\/ 100%\u003c\/p\u003e\n\u003cp\u003eF Darton \u0026amp; Co. Logo on the face and rear  \u003c\/p\u003e\n\u003cp\u003ePercentage Relative Humidity\u003c\/p\u003e\n\u003cp\u003eBritish Made\u003c\/p\u003e\n\u003cp\u003eSerial No. 5228\u003c\/p\u003e\n\u003cp\u003eA hair hygrograph measures the humidity (or dew point). It works by using the principle that a human or horse hair changes length depending on the level of humidity in the air. This particular instrument was manufactured in the 1940s but the design dates back much earlier. They were also sold as pocket instruments, although you'd need fairly big pockets or a lab coat for this one!\u003cbr\u003e\u003cbr\u003eThe only other place where I have seen one of these instruments is online as part of the \u003ca href=\"https:\/\/collection.sciencemuseumgroup.org.uk\/objects\/co54620\/precision-hair-hygrometer-by-f-darton-and-co-ltd\" rel=\"noopener\" target=\"_blank\"\u003eScience Museum Collection\u003c\/a\u003e\u003c\/p\u003e\n\u003cp\u003ePlease click on the following link for more \u003ca href=\"https:\/\/mullardantiques.co.uk\/collections\/meterological-weather\" target=\"_blank\"\u003evintage weather \/ meterological instruments\u003c\/a\u003e \u003cbr\u003e\u003cspan style=\"border-top-left-radius: 2px; border-top-right-radius: 2px; border-bottom-right-radius: 2px; border-bottom-left-radius: 2px; text-indent: 20px; width: auto; padding: 0px 4px 0px 0px; text-align: center; font-style: normal; font-variant-caps: normal; font-weight: bold; font-stretch: normal; 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background-size: 14px 14px; background-color: #bd081c; position: absolute; opacity: 1; z-index: 8675309; display: none; cursor: pointer; border: none; -webkit-font-smoothing: antialiased; background-position: 3px 50%; background-repeat: no-repeat no-repeat;\"\u003eSave\u003c\/span\u003e\u003cspan style=\"border-top-left-radius: 2px; border-top-right-radius: 2px; border-bottom-right-radius: 2px; border-bottom-left-radius: 2px; text-indent: 20px; width: auto; padding: 0px 4px 0px 0px; text-align: center; font-style: normal; font-variant-caps: normal; font-weight: bold; font-stretch: normal; font-size: 11px; line-height: 20px; font-family: 'Helvetica Neue', Helvetica, sans-serif; color: #ffffff; background-image: url(data:image\/svg+xml; base64,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); 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Ltd.","offers":[{"title":"Default Title","offer_id":55332365795703,"sku":null,"price":150.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0303\/5122\/8972\/files\/Vintage_1940s_F_Darton_Relative_Humidity_Meter_Precision_Hair_Hygrometer.jpg?v=1750597404","url":"https:\/\/mullardantiques.co.uk\/en-us\/products\/vintage-1940s-f-darton-relative-humidity-meter-precision-hair-hygrometer","provider":"Mullard Antiques and Collectibles","version":"1.0","type":"link"}