We use a company called Novatron to calibrate ours (they also supply the papers) but these are old bimetallic strip and horsehair strand rotating drum thermohyrographs so it’s a bit of a specialist job. If yours are ones that can be calibrated by the owner, according to whatever instructions you have, then you’ll need something called a whirling hygrometer to set the humidity properly. This uses two thermometers, one with a dry end, one with a wet end and a fair bit of flailing it around to work out relative humidity by the difference in temperatures due to evaporation (you get a sort of slide rule thing with it so you can work it out), it’s the only really accurate way of doing it.

Andrew.

From: Social History Curators Group email list [mailto:[log in to unmask]] On Behalf Of Catherine Simpson
Sent: 03 June 2015 15:03
To: [log in to unmask]
Subject: Thermo-Hygrograph [Scanned]

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Hello all,

I was wondering if you could provide me with a little bit of advice.

I need to get our thermos-hygrographs calibrated but am a little unsure as to the procedure involved. Is it a case of ordering equipment and calibrating them ourselves or, would we send them away for this process? If anyone is able to give me some advice on this or point me in the right direction, I’d be very grateful?

Many thanks

Catherine

Catherine Simpson | Collections Officer | Royal Shakespeare Company

Waterside, Stratford-upon-Avon, Warwickshire, CV37 6BB

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