Michell Instruments is announcing a rugged, self-contained hygrometer designed specifically for the measurement of trace moisture content in high purity gases.

The Pura pure gas dew-point transmitter is said to represent a landmark in moisture transmitter design, giving high accuracy, stability and repeatability in a specialised application, and at a highly competitive price.
The Pura has been developed for and tested by the semiconductor industry to measure trace moisture in the high purity gases used in the processing of silicon wafers in semiconductor fabrication plants.
Historically trace moisture measurement has been a difficult exercise, demanding the use of complex moisture analysers or expensive analytical techniques.
The Pura provides on-line measurement of dew-point temperatures down to -100ûC, (equivalent to less than 15 parts per billion), and provides indication down even lower to -120ûC (less than 0.2 parts per billion).
The Pura transmitter is suitable for large-scale integration into a semiconductor fabrication plant or high purity gas line.
Pura is deceptively simple. Its self-contained transmitter module has been designed to fit seamlessly into pure gas processes and give continuous and reliable measurement thereafter. Installation is also simple.
The male VCR gas connection ports are set at a pitch of 120 mm to fit into a standard MFC footprint. The whole unit is only 152 mm in height and weighs less than 500 g. Pura is claimed to provide the ultimate flexibility in operation and is powered by any regulated 12 to 28 V dc source.
Pura's sensor housing is fabricated from stainless steel with an internal 0.25 micron electro-polished finish for minimal moisture adsorption.
The gas connection ports are supplied capped for cleanliness. Indeed, Pura can be delivered clean and double-bagged to the class 100 clean room standard, if specified.
Furthermore, Pura is delivered fully calibrated and ready to use. The 4 - 20 mA output can be connected to a process indicator or centralised control system, or the RS485 text output can be used to connect directly into a suitable computer system.
Internal volumes have been designed to a minimum. This ensures the fastest possible response speed in commissioning and also when a moisture event occurs. The sensor body seal is rated to 10 - 9 torr while the whole system will handle pressure right up to the VCR coupling rated maximum of 24 MPa.
While Pura is shipped ready to use, calibrated precisely at thirteen points across its measurement range against transfer standards traceable to NIST and NPL, it is also user-customisable.
The 4 - 20 mA output can be user set over any part of the 140ûC dew point range, with a minimum output span of 1ûC.
Also, the factory pre-set alarm signals, providing over-range, under-range and sensor fault conditions, can also be easily re-set to suit the user's own application and system needs.
Adjustment of all these parameters is achieved through a simple PC-based user interface, supplied free of charge with every Pura on request.
Meanwhile, Michell Instruments has launched a new website that has been developed as a source of in-depth information and advice for everyone interested in humidity control and process instrumentation.
At the heart of the site is an interactive product locator that helps the user to find the most suitable product by means of a few simple questions about the application and measurement requirements.
Other new features include searchable FAQs, information on sensor and dew point measurement technologies and a special Secure Zone, created exclusively for Michell Instruments' worldwide distributors.
The Secure Zone is intended toopen a dialogue between Michell and its distributors, where sales and marketing information and tips can be freely exchanged. The Zone also contains confidential downloads, on-line order tracking and marketing design templates.

For more information, visit www.michell-instruments.com