Pura
Dew-Point Transmitters
Pure Gas Moisture Transmitter
This small pure gas transmitter is a rugged, self-contained hygrometer designed specifically for the
measurement of trace moisture content in ultra high purity gases.
Simple to use and install, the Pura is available in two-wire, three-wire and hazardous area versions
and is fully configurable to meet specific needs.
Highlights
• Measurement range down to -120°C (-184°F)
dew point (1ppbV)
• Stable and repeatable measurement
• Analog and digital output
• Simple installation
• VCR process connections
• Optional display / alarm unit
• Compact design
• Fast response
• Optional hazardous area approval
• Service exchange program
www.michell.com
Applications
• Pure gases
• Semiconductor manufacture
• Fibre optic production
• Electronic component manufacture
• Optical coating processes
• Industrial gas production and distribution
Dew-Point Transmitters
Pure Gas Dew-Point Transmitter
In many high purity gas applications, such as the semiconductor
industry, the residual moisture content of the gas is critical to
the satisfactory operation of a process.
Historically trace moisture measurement has been problematic,
demanding the use of complex moisture analysers or expensive
analytical techniques. Now Michell has brought to market
a simple, economical and very effective solution for on-line
measurement of dew-point temperatures down to -120°C
(-184°F) (equivalent to less than 1 part per billion).
The Pura transmitter benefits from Michell’s experience and
expertise in the production and calibration of impedance dewpoint sensors. Incorporation of industry standard materials and
manufacturing processes gives the first low cost transmitter
suitable for large-scale integration into a semiconductor
fabrication plant or high purity gas line.
Simple To Use
This self-contained transmitter module has been designed to
fit seamlessly into your pure gas process and give you the
measurement you need - continuously and reliably.
Pura’s sensor housing is fabricated from cold drawn stainless
steel with an internal 0.25 Ra μm electro-polished finish for
minimal moisture adsorption and cleaned to oxygen standards.
The transmitter is delivered fully calibrated and ready to use.
The calibrated 4-20 mA output can be connected to a Michell
process indicator or centralised control system.
The unit is designed to have minimal internal volume. This
ensures the fastest possible response speed in commissioning
and also when a moisture event occurs. The sensor containment
seal is rated to 10-9 torr whilst the whole system will handle
pressure right up to the VCR coupling rated maximum of 240
Barg (3480 psi).
Customisable Information
While Pura 2-wire is shipped ready to use, calibrated at
dew point intervals across its measurement range against
transfer standards traceable to NIST and NPL, it is also usercustomisable. The 4-20 mA output can be user set over any part
of the operating range, with a minimum output span of
Also,
the factory pre-set alarm signals, providing over-range,
under-range and sensor fault conditions, can also be easily reset to suit your own application and system needs. Adjustment
of all these parameters is achieved through a simple PC-based
user interface, available as a download at www.michell.com
10°C
1°C.
Easy Installation and Operation
Pura is simple to install. The ¼” male VCR gas connection ports
are set at a pitch of 120mm (4.72 in) to fit into a standard Mass
Flow Controller footprint. The whole unit is only 150mm (5.9 in)
in height and weighs less than 500g (1.1 lb). Pura is a two or
three wire transmitter, providing ultimate flexibility in operation
and powered by any regulated 12 to 28 V DC source (max 25
mA).
Optional Monitor
If the application calls for the dew point or moisture content to
be displayed then the Pura can be supplied as a hygrometer,
with an Online (standard) or Advanced Online panel mounted
display. Our range of monitors are simple to connect and also
acts as a power supply for the Pura Transmitter.
Service Exchange/Recalibration Program
Michell offers two services for customers who want minimum
downtime and equipment traceability:
Sensor Exchange – customers place an order for a
guaranteed, reconditioned sensor. When this arrives, they
exchange it for the installed sensor which is returned to Michell,
resulting in zero process downtime.
Recalibration – customers return their installed sensors to
Michell, where they are inspected, checked and recalibrated
before being returned. This provides on-going sensor traceabilty
for the process.
Other Options
Mechanical options:
• Premium - Clean room cleaned, inert gas filled, double
bagged, 1/4” VCR.
• OEM - Clean room cleaned, single bagged.
• Sensor - 1/2” VCR connections.
Electrical Options:
• PUR-TX-2W - 2 wire 4 to 20mA
• PUR-TX-3W - 3 wire 4 to 20mA
• PUR-IS-2W - 2 wire hazardous area 4 to 20mA
Display Options:
• Advanced Online - 5 digit display, user configurable
• Online - 4 Digit display
www.michell.com
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