A hygrograph uses a length of hair to record changes in humidity. Models are available with either a clockwork motor or a quartz clock, switchable between one, seven or 31 day rotation.

A thermograph records air temperature and relative humidity on a continuous basis. It is used to monitor the optimum temperature and humidity where these factors are important. Models are available with either a clockwork motor or a quartz clock, switchable between one, seven or 31 day rotation.

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