Customized OEM Solutions for Humidity Measurement

Standardization is not always king: PST's flexibility in an OEM project sample

Despite our best efforts, there are always projects that arise requiring a solution beyond our standard product range. Whilst we cannot make new products for every requirement the ability to develop customized solutions is vitally important for many of our OEM (Original Equipment Manufacturer) customers.

For any OEM project we ensure first that we fully understand the application and the customers' key requirements. Very often through deeper understanding both, we and our clients, discover new important details or ways to solve their challenges. Very often standard products can in fact be used and this is always favorable as it typically reduces project risk, reduces testing time, and lowers development time.

Understanding the application

This application required humidity measurement in hydrogen peroxide vaporization sterilization processes. Our client produces fixed and mobile units that are used to perform sterilization cycles, both generating and removing the vaporized hydrogen peroxide. Humidity measurement forms a critical part of the control input for this cycle ensuring both performance and safety.

Hydrogen peroxide whilst being highly toxic to organisms is also highly corrosive to electronics and humidity sensors. Our client has found their existing sensors simply could not survive or give stable readings between planned service intervals.

Proof of concept

Initially, we had to confirm that our sensors could survive and perform in this aggressive application. Rotronic has over 50 years’ experience with humidity measurements and the company was founded around our own in-house polymer technology. Despite this, our standard sensors would not survive long term so instead we made use of a specially developed corrosion-resistant sensor. Using this polymer on standard products we were able to show in real application client testing that we could provide a technology with low drift and high accuracy over time.

From concept to solution

Following initial testing there were further challenges. As we had to fit our technology into an existing product range our client required a retrofit solution. They had very specific physical connections and needed a small form factor to fit and perform in their products. Our standard probes simply were not suitable.

Instead, our ROPCB OEM humidity module was selected with additional adaptions including;

• New power and output connections
• Application of a conformal coating to provide additional protection to the bare PCB
• Fixed output failure mode in the event of sensor failure detection (this could be detected by the client device and give a specific error code for end users).

The final product ensured excellent performance in a cost-effective module that could be directly retro fit into new and existing products.

Operating Range	0…100%rh & -40…60°C
Output signal humidity	0…1V = 0…100%rh, UART digital
Output signal temperature	0…1V = -40…60°C, UART digital
Accuracy	±1.5%rh (10…90%rh, 23°C ±5°C) ± 0.3K (0…50°C)
Stability	< 1%rh per year <0.2°C
Power supply	3.3V … 5V
Electronics protection	Polyurethane conformal coating
Failure mode	Both outputs to 1.0V in event of sensor failure detection
Dimensions	54x35x5mm

Continuous improvement

As a quality focused customer, the solution and products were under continuous testing and review. Over time it was discovered that some units would fail the rigorous standards required. Working together on route cause analysis we identified several improvement steps at in both supplier and client processes. Through better understanding we put in place client training and education to ensure improved handling in the client’s production and service teams. In our calibration facilities additional stress testing and quality checks were put in place quickly to ensure all products shipped were robust. Finally ongoing reviews were made to track any changes in product performance over time.

Creating a partnership

The project did not stop here. Whilst our initial solution was and continues to be highly successful, we still work closely with our client. In newer products they have been able to design in our standard products for easier installation and servicing. In addition, as we evolve our products, we ensure clients can test and review product changes. Partnerships such as this helps us to continue to offer the best solutions for any humidity measurement application.

Your partner for humidity measurement in any application

PST offers an unmatched range of humidity products built around our wide range of in-house sensor technologies. Using this wealth of knowledge and technology we offer three approaches for our OEM customers.