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Pura is a small, rugged, self-contained hygrometer transmitter designed specifically for the measurement of trace moisture content in ultra high purity gases used for semiconductor manufacturing, fiber optic production, optical ciating processes and pure gas production.

Simple to use and install, Pura is available in 2-wire, 3-wire and hazardous area versions with VCR process connections and optional display/alarm units. It is fully configurable to meet specific needs.



Sensor Type

Michell Advanced Ceramic Moisture Sensor


-120 to -40°Cdp (calibrated from -100 to -40°C)

(-184°F to -40°Fdp calibrated from -148 to -40°F)


±1°C from -40 up to -60°Cdp (-40 up to -76°Fdp)

±2°C from -60 up to -100°Cdp (-76 up to -148°Fdp)
±4°C from -100 to -120°Cdp (estimated) (-76 up to -148°Fdp)

Operating Pressure

Minimum 10-7 Pa (10-9 torr)

Maximum 24 MPa (240 barg)

Operating Temperature

-40 to +60°C (-40 to +140°F)

Flow Rate

1 to 5 Nl/min (2.11 to 10.59 scfh)



Nominal 24 V DC, 10-28 V DC maximum current 25 mA 2 or 3-wire configuration


PUR-TX-2W: 4 to 20mA 2-wire

PUR-TX-3W: 4 to 20mA 3-wire
PUR-AOL-SEN only: Digital String (RS485)

Cable with Display

PUR-OL & PUR-IS-OL: 2m (standard) (6.56ft) / 5 or 10m (16.4 or 32.8ft) (optional)

PUR-AOL: 2m (standard) (6.56ft) / 5 or 10m (16.4 or 32.8ft) (optional)


Sensor Block

Premium and OEM version: Cold drawn stainless steel, 0.1 - 0.2 Ra µm electro-polished internal finish

Pressure Connections

Premium and OEM version: ¼" male VCR connection

Pura Sensor version: ½" male VCR connection

Installation Profile

Premium and OEM version: 120mm (4.72in) pitch, drop in across gas port face seals

Zero pipe clearance required
2 off M4 x 0.7, 7mm (0.03, 0.28in) deep mounting holes in block, diagonally opposed at 20 x 20mm (0.79 x 0.79in) pitch 
Pura Sensor version: fits into user's ½" VCR configured port

Overall Dimensions

Premium and OEM version: 120 x 35 x 150mm (4.72 x 1.38 x 5.9in) (w x d x h)

Pura Sensor version: 132 x Ø35mm (5.2 x Ø1.38in)


Premium and OEM versions: 450g (0.99lb)

Pura Sensor version: 180g (0.4lb)


Pura Premium: Double bagged and sealed in UHP inert gas 

Pura OEM & Pura Sensor: Single bagged in 1000 gauge polythene
All options: shipped individually in profiled sponge protection and carton
Pura Sensor version supplied with protective guard over sensor surface for transportation and handling

Service Exchange

Available on the Pura Sensor (SEN) ½" VCR connection


Advanced Online Monitor: PUR-AOL

Online Monitor: PUR-OL

Measurement Units

°F, °Cdp; ppmV and ppbV with user-selectable range and resolution

Simple display defined by 2-wire sensor input

Secondary measurement variable

Pressure via external transducer 0-30 MPa (300 variable barg/4351 psi)

Completely user-configurable for any industry standard transducer
Automatic compensation for ppmV and ppbV

ppmV with no line pressure correction input available with PUR-TX-2W & PUR-IS-2W

Power Supply

Universal 85 to 265 V AC; 95 to 370 V DC

100 to 240 V AC (+10, -15%) 50/60 Hz

Ingress Protection

IP54 (NEMA 12); IP66 (NEMA 4X) for front panel only with optional cover

IP65 front panel (IP20 rear panel)

Operating Temperature

0 to +50°C (+32 to +122°F)

0 to +50°C (+32 to +122°F)


2 off 10 A / 240 V c/o fully user-configurable: can accommodate full range for selected engineering unit + sensor fault alarm functions

Alarm 1 relay: single pole make contact, rating 3 A @ 250 V AC 

Alarm 2 relay: changeover contacts, rating 5 A @ 250 V AC

Display Resolution

5 Digit

4 Digit

Outputs: Analog

4-20 mA fully user-configurable and scaleable for range

0-20 or 4-20 mA fully user-configurable and scaleable for range

Outputs: Digital

RS232: provides 2-way communication - full data access to user and total availability of all set-up options

RS232: provides 2-way communication - full data access to user and total availability of all set-up options


Power Supply

18 to 36 V AC; 9 to 60 V DC

24 V DC


1 or 2 further 5 A relays (max 4 in total) n/o type fully user-configurable: can accommodate full range + full unit choice + sensor fault alarm functions

1 further optional relay - refer to factory

Outputs: Analog

0-10 V fully user-configurable and scaleable for range

0 to 10 V output using 500 Ω shunt resistant

Outputs: Digital



.  Measurement range down to -120°Cdp (-184°Fdp) (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

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