Humidity control is a crucial element for a wide variety of experiments. Yet, often naive methods are used that do not yield stable regulation of the humidity, are slow, or are inflexible. PID-based electropneumatic humidistats solve these problems, but commercial devices are not widespread, typically proprietary and/or prohibitively expensive. Here we describe OpenHumidistat: a free and open-source humidistat for laboratory-scale humidity control that is affordable (<500 EUR) and easy to build. The design is based around mixing a humid and dry air flow in varying proportions, using proportional solenoid valves and flow sensors to control flow rates. The mixed flow is led into a measurement chamber, which contains a humidity sensor to provide feedback to the controller, to achieve closed-loop humidity control.
Cite
@article{arxiv.2112.08500,
title = {OpenHumidistat: Humidity-controlled experiments for everyone},
author = {Lars B. Veldscholte and Sissi de Beer},
journal= {arXiv preprint arXiv:2112.08500},
year = {2022}
}