New technique offers accurate moisture measurement

The HygroTrace meter from GE Sensing uses aluminium oxide technology vastly improves sensor speed of response to provide parts per billion moisture measurement in minutes.

Moisture measurement in low parts per billion measurement ranges for ultra-high purity (UHP) gases is critical to a variety of semiconductor, LCD, and other manufacturing processes.

HygroTrace uses a newly patented technique to provide accurate and reliable measurement for 0-100 parts per billion moisture levels with the sensitivity and speed of response matched only by current technology analysers that are much larger in size and more expensive in price.

Typical semiconductor applications include measurement of moisture in UHP gas delivery and distribution systems and point-of-use moisture measurement protection.

Current technologies for low parts per billion moisture measurement include tunable diode laser absorption spectroscopy (TDLAS), vibrating quartz crystal, and phosphorous pentoxide.

However, these technologies typically require a rack mount instrument package that is relatively large in size and includes complicated parts and temperature control.

As a result, these analysers cost US $20,000-50,000 per point of measurement.

The new HygroTrace meter from GE Sensing uses aluminium oxide technology with a newly patented technique that vastly improves sensor speed of response to provide parts per billion moisture measurement in minutes.

In addition, HygroTrace has the form factor of a transmitter package with the only wetted parts being essentially a flow-through quarter-inch VCR tee fitting.

The HygroTrace package is 80-90% smaller than competitive analysers and cost 50-70% less.

"Customers have always liked the form factor of aluminium oxide moisture sensor technology for moisture measurement in UHP gas systems because it's small and it can be mounted closer to the sample point than other technologies", says John Kerney, Moisture Product Manager for GE Sensing.

"Traditional diffusion-based aluminium oxide sensors have proved just too slow in terms of response time that customers need".

"We took a fresh approach knowing that these sensors tend to wet-up very rapidly".

"The new sensor technology employed in the HygroTrace applies a temperature pulse to 'dry' the sensor".

"Then the re-adsorption rate is measured while holding a constant sensor temperature".

"This measurement is proportional to the moisture concentration in the sample gas and provides the sensitivity and response time needed to effectively measure parts per billion levels of moisture".

HygroTrace features a large integrated backlit display, which users can easily read from several feet away.

An integral six-button keypad allows users to program the unit for output range and to check on performance.

The unit is loop-powered using a 20-28V DC source and provides a 4-20mA output proportional to a user-programmed range.

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