Cavity Ring-Down Spectroscopy (CRDS)Trace Moisture Analyzer
Cavity Ring-Down Spectroscopy (CRDS) trace moisture analyzer is an absolute measurement method and can measure trace moisture with fast response, high accuracy, and long-term reliability. It provides reliable trace moisture control for R&D and manufacturing with advanced technologies such as high purity gases for semiconductors, all solid-state batteries, industrial furnaces and more.
CRDS measuring principle
Reliable, accurate, and fast trace moisture measurement method
In CRDS, a beam from a laser diode enters a cavity with two high reflective mirrors to detect an amount of laser absorption by the moisture in the sample gases in the cavity. When the laser is on, the cavity rapidly fills with circulating laser light, and a small amount of light leaks from one of the mirrors in the cavity. The amount of trace moisture in the cavity can be analyzed by detecting this leakage light and measuring the ring-down time it takes for the leakage light to decay to 1/e of its initial intensity.
Why is CRDS referred to as an absolute measurement method?
Direct measurement method without calibration curve
Moisture meters that use moisture adsorption and desorption, such as aluminium oxide sensors calculate the amount of moisture based on the change in the electrical state such as the capacitance of
the sensor due to the amount of moisture. A calibration curve for each sensor is set independently by a manufacturer, and any deviation from the calibration curve due to sensor drift in use or over time must be adjusted each time based on the results of a comparison calibration against a standard.
CRDS is referr to as an absolute measurement method because it can be calculated directly from measured values of known physical constants without the need for calibration curves, and in principle, does not require calibration against a standard.
The light decay time, which is the measuring principle of CRDS, does not depend on the light intensity of the incident light, so even if the light intensity decreases due to the ageing of the laser, the measurement accuracy is not affected. Therefore, it has the advantage of high reliability of long-term measurement and the frequency of periodic calibration can be reduced.
DewTracer series
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Cavity Ring-Down Spectroscopy trace moisture analysis systemDewTracer mini CRDS-H2O
TDewTracer mini CRDS-H2O is the world's smallest and most innovative Cavity Ring-Down Spectroscopy (CRDS) trace moisture analyzer. It can measure trace moisture in the range of 12 ppbv ~ 20 ppmv (-100 ~ 55 °CDP) with high speed, high accuracy and long-term reliability.