Verification of reliability of TDLAS-based dew point hygrometer

Ken Sugimura, Shinyei Technology Co. (JP)

The demand for hygrometers usable in a wide range with fast response time has been increasing in various industrial fields. However, many different kinds of existing sensors, such as capacitive humidity sensors and chilled mirror hygrometers tend to show slow response in a low humidity range. This is because these sensors need to detect moisture at equilibrium state and the low humidity level causes the moisture to require long time to attain the equilibrium. In order to solve this problem, Shinyei Technology Co., Ltd. has developed a new dew point hygrometer T-1 based on tunable diode laser absorption spectroscopy (TDLAS).
In contrast to the equilibrium-based sensors, the T-1 can directly detect water molecules in gas phase and therefore show much faster response time: for example, ≤ 6 sec, 90% of 0 to -50 °C DP and 2 sec, 63% of 10 to 90 %rh. While the T-1 can measure the dew point until -70 °C DP as a lower limit, the optional internal heater can be equipped to prevent the moisture condensation in the measurement system and this optional heating allows the T-1 to measure the dew point up to 50 °C DP. In terms of accuracy, the T-1 can perform the measurement almost as precisely as chilled mirror hygrometers. Besides, the T-1 is applicable to several kinds of background gases such as N2, O2, He, etc. as well as corrosive gases as a future possibility.
For the purpose of verifying the reliability of the new dew point hygrometer T-1, the following evaluations were conducted with the cooperation of the National Metrology Institute of Japan (NMIJ): long term stability test more than 8 months, repeatability and reproducibility test at -70/ -50 / -30 °C DP.


Pen Profile

In charge of sales of TDLAS (Tunable Diode Laser Absorption Spectroscopy) sensor systems. Also familiar with chilled mirror dew-point meters and electronic hygrometers as well as calibration and field services relating to moisture measurements. Involved in the co-development project for TDLAS sensors with the National Institute of Advanced Industrial Science and Technology (AIST), one of the largest public research organizations in Japan.

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