Dewmetric Instruments inc.

2024-08-06

As I needed a reference dew point gas to measure with my prototype hygrometer (first image) and did not have the option to buy a reference gas generator. I decided to design one based on saturated salt solution. I was inspired by an article published in Measurement that uses pneumatic valves to switch from one salt solution to the other. I design one using an erlenmeyer with a specifically 3D printed head. It is mounted in a 2020 aluminum extrusion frame. I wanted a more compact system.

Instead of using a nitrogen gas source that passed through the system, I use a fan to circulate the gas in a closed loop. To control the bottle selection I use the Nextion Display 8 IO port with a 8 Relay Board module. It is simple to program and has a serial interface to enable simple remote control using Node-Red.

2023-06-29

First official update of the instrument development. I am more in the software development, focusing on the user interface UART (com port) management. The QCM (Quartz Crystal Microbalance) board will be transferred in the smaller version of an experimental setup very close to the final dew point sensor module. A first dew point manual tracking has been performed with very encouraging results. Thermo-electric power PCB module has not been completely tested but works very well without generating noise on the QCM. Next steps will focus on completing measurements from the external thermistor and for the optional pressure sensor. Up to now, frequency, temperature and QCM load are measure within needed specification. The controller board design is still in progress. I wait until I can get a full controlled dewpoint measurement before completing it. A lot of fun to come in the next months. 

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