Sensor technology has changed dramatically over the past few years. Previously, customers purchased the sensor elements and electronics and calibrated a sensor themselves. The development of improved electronics, MEMs technology and efficient manufacturing technology has created a new humidity sensor market - fully calibrated humidity sensors with an I2C output. Many companies are offering models with similar features.
Yet, price and performance does vary significantly between models, making it important for users to understand the the performance of a humidity sensor over the entire range. This data is often well hidden in fine print in data sheets.
IST, the supplier of our HYT digital humidity elements and the new sensor elements P14, tested 4 different humidity sensors at 85% rH @ 30C for 65 hours. 2 competitors, the HYT271, and the P14 humidity element were tested. The 2 competitors units showed a 1.25% and 2.5% deviation in readings compared to only 0.17% for the HYT271 and 0.09% for the P14.
What does this mean for designers trying to choose a humidity sensor? The humidity sensor element (such as P14) plays a critical role in the performance of a fully integrated and compensated humidity sensor. Electronics is limited in compensating for poor signals a sensor element sends. The combination of good sensor elements and electronics is the key to sensor design.
The integration of a sensor element and electronics is fairly straightforward. However, if performance over time and at extreme conditions is critical for your application, take the time to research the quality and stability of the sensor element used. Saving a little in upfront component cost could end up costing you much more in the long run!