OpenHumidistat: Humidity-controlled experiments for everyone

TL;DR

OpenHumidistat is an affordable, open-source device that enables precise, closed-loop humidity control for laboratory experiments, addressing limitations of naive methods and commercial solutions.

Contribution

It introduces a low-cost, easy-to-build humidistat using proportional valves and sensors, making humidity regulation accessible for scientific research.

Findings

Affordable (<500 EUR) design

Effective closed-loop humidity control

Easy to assemble and customize

Abstract

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.