Tips and Tricks - Soft Matter
Design, construction, and testing of an accurate low-cost humidistat for laboratory-scale applications
Sustainable Polymer Chemistry Group, Department of Molecules and Materials MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands
Accepted: 24 March 2021
Published online: 5 April 2021
Stable and precise control of humidity is imperative for a wide variety of experiments. However, commercially available humidistats (devices that maintain a constant humidity) are often prohibitively expensive. Here, we present a simple yet effective humidistat for laboratory-scale applications that can be easily and affordably (<€250) constructed based on an Arduino Uno as microcontroller, a set of proportional miniature solenoid valves, a gas washing bottle, and a humidity sensor. The microcontroller implements a PID controller that regulates the ratio of a dry and humid airflow. The design and implementation of the device, including a custom driver circuit for the solenoids, are described in detail, and the firmware is freely available online. Finally, we demonstrate its proper operation and performance through step response and long-term stability tests, which shows settling times of approx. 30 s and an attainable relative humidity range of 10–95%
© The Author(s) 2021
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