Most greenhouse owners purchase a simple thermometer and hygrometer that can be installed inside the greenhouse so they can keep an eye on temperature and relative humidity.
There weren't any high tech gadgets, like a hygrometer, to ensure that batches of wine turned out well.
He also invented an improved form of hygrometer, a description of which, together with accounts of various observations and experiments made by him, was published in the Phil.
The simplest mechanical hygrometer uses a single human hair to determine humidity.
The cautious grower will always monitor the humidity in his growroom which is measured by another simple device called a hygrometer.