Michell Instruments Cermet II Specifications

Dew-Point Transmitters

Cermet II

Hygrometer

The hygrometer of choice for the measurement of dew point, temperature, or gaseous moisture
applications with a choice of units of measurement or where pressure compensation is required.

Highlights

• Wide measurement range, calibrated

-100 to +20°C (-148 to +68°F) dew point

• ±1°C (±1.8°F) dew point measurement
accuracy

• Pressure sensor input

• Up to 4 alarm relays

• User selectable units of measurement

• Easy to read display

• Analog and digital outputs

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Applications

• Industrial gases

• Dried compressed air

• Welding gases

• Glove boxes

• Medical gases

• High voltage switchgear (SF

)

6

Dew-Point Transmitters

Cermet II Hygrometer

Complete On-Line Dew Point Solution

Cermet II is the intelligent choice for reliable on-line
measurement of moisture in virtually any gas, across many
applications. Cermet II combines Michell’s Advanced Ceramic
Moisture Sensor and a monitor unit that can be located up
to 1200 m apart (3930 ft). While Cermet II is so simple to
use, it has the fl exibility to be applied to almost any humidity
measurement application. The instrument can display
measurement units in °C or °F dew point, ppmV, lb/mmscf or
g/m3 across the measurement range -100 to +20°C (-148 to
+68°F) dew point at pressures up to 5000 psig. The Cermet II
also can accept a pressure signal from a pressure transmitter
(optional) providing the means of active pressure compensation
for concentration units of measurement.

Cermet II Monitor

The Cermet II Monitor is a fully self-contained display system
in a 1/8 DIN panel mounting case that indicates the measured
humidity parameter and performs pressure compensation (if
required). Cermet II also provides current and digital outputs
and two 10 A alarm relays. It is protected to NEMA 12 and can
be supplied with an optional front panel providing a NEMA 4
rating. Its operating temperature range is -20 to + 50°C (-4 to
+ 122°F).

Cermet II is supplied with a 4-20 mA output, which is fully
confi gurable for range and scale as standard. In addition, a
2-way RS232 digital signal is provided which gives full data
access to the user. Optionally a 0-10 V confi gurable analog
output can be specifi ed, as can an RS485 2-way digital output.

Applications

Cermet II can provide the solution to both energy management
and quality assurance in the supply of pure gases and
compressed air from heat regenerative, adsorption dryers. The
durability of the Advanced Ceramic Moisture Sensor provides
long term service in applications such as pipeline drying using
vacuum and dry gas purging techniques.

Cermet II Sensor

The Cermet II Sensor uses Michell’s Advanced Ceramic Moisture
Sensor technology with on-board intelligence. This smart
sensor has a measurement range of -100 to +20°C dew point
(-148 to +68°F) at pressures up to 45 MPa (450 barg/6500
psi) max and offers a superior measurement accuracy of better
than ±1°C dew point from -60 to +20°C (±1.8°F from -76
to +68°F). From -100 to -60°C dew point the measurement
accuracy is ±2°C dew point (±3.6°F from -148 to -76°F dew
point). The on-board processor in the sensor electronics enables
excellent performance, reliability and interchangeability of
sensors. Cermet II’s sensor is designed to perform in harsh
environments. Constructed in stainless steel, the sensor is also
protected to NEMA 4 and has an operating temperature range of

-40 to +60°C (-40 to +140°F).

Extreme Flexibility

The dew point of any gas will vary with pressure. When
calculating concentration units of measure, Cermet II can
compensate for these variations either by using of a live
pressure transducer input, or by using a pressure factor input
via the instrument front panel.

For control of external devices Cermet II is supplied as with two
10 A, 240 V AC fully user confi gurable alarms as standard. These
can be set over the full operating range of the instrument, with
variable hysteresis for any chosen engineering unit. The alarms
can also be confi gured to fl ag sensor or cable fault conditions.
An additional two alarms can be added if required.

Power station (Peterhead CS)

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Dew-Point Transmitters

Technology:
Impedance

The Cermet uses Impedance technology, based on Michell’s
advanced ceramic sensor. The operation of this sensor depends
on the dielectric property of water molecules absorbing onto an
active porous insulating layer sandwiched between two layers of
conductive material deposited on a ceramic substrate.

Water has a very high dielectric compared to the dielectric of
the active layer and the background of the carrier gas so it can
be detected easily.

The active layer is very thin – less than one micron and the
porous top conductor that allows water molecules to penetrate
into the active layer is less than 0.1 micron thick. This allows
the sensor to respond very rapidly to changes in the moisture
surrounding it both when moisture decreases (drying) and
increases in the sensor environment.

Permeable Gold film

g

g

Hygroscopic Mono-layer

Base Electrode

g

Ceramic Substrate

g

Moisture
Molecules

g

Michell ceramic sensor tile layers

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Dew-Point Transmitters

Technical Specifi cations

Sensor

Measurement Range -100 to +20°C (-148 to +68°F) dew point
Accuracy (dew point) ±1°C from -60 to +20°C dew point

Enclosure Stainless steel
Ingress Protection NEMA 4 in protection and accordance with

Operating Temperature -40 to +60°C (-40 to +140°F)

Storage Temperature -40 to +109°C (-40 to +165°F)
Operating Pressure From vacuum to 40 MPa (400 barg/5801 psig) (max)
Flow Rate 1 to 5 l/min (2.1 to 10.5 scfh)
Gas Velocity 0 to 10m/sec (0 to 32.8 ft/sec)
Process Connection 5/8” UNF parallel thread
Sensor Calibration Traceable to NIST and UKAS

(±1.8°F, -76 to +68°F dew point)
±2°C from -100 to -60°C dew point
(±3.6°F, -148 to -76°F dew point)

standard NEMA 250-2003 and IP66 in accordance
with standard BS EN 60529:1992

compensated over -20 to +40°C (-4 to +104°F)

Analyzer

Measurement Units °Cdp, °Fdp; ppmV with user

Resolution 0.1 °C from -80 to +20°C dew point

Secondary
Measurement Variable

Alarm Relays Two user adjustable isolated 10A form ‘C’

Outputs:

Analog

Digital

Power Supply Universal 85 to 265 V AC, 50/60 Hz or 95

selectable range and resolution; lbs/MMscf
range dependent on pressure (natural
gas); g/m3 (natural gas). Digital
processing and linearization with active or
passive pressure compensation

(0.18°F, -112 to +68°F dew point)
1°C from -100 to -80°C dew point
(1.8°F, -148 to -112°F dew point)

Pressure using an optional external
transducer over a range of 0-45 MPa (450
barg/6527 psig. Completely user-confi gurable for
any industry standard transducer with an
4-20 mA output. Automatic compensation for
ppmV, lbs/MMscf and g/m3 units.

rated at 240 V AC or 24 V DC

4-20 mA as standard (max load 500 Ω)
user confi gurable and scalable
RS232

to 370 V DC

Operating Conditions

Operating Temperature

Ingress Protection

Analyzer:

Sensor:

Analyzer:

Sensor:

0 to +50°C (32 to +122°F)

-20 to +50°C (-5 to +122°F)

IP54 (NEMA 12) standard (front panel only)
IP66 (NEMA4) with optional cover (front panel only)
IP66 (NEMA4)

Options

Outputs

Alarm Relays 1 or 2 additional 5 A relays (max 4 total) n/o type

Power Supply 18 to 36 V AC; 9 to 60 V DC
Cable Standard 2 m (6.56 ft) (1200 m/3937 ft max)

Analog:

Digital:

0-20 mA optional (max load 500 Ω)
0-10 V optional (min load 5 K Ω)
both user confi gurable and scalable
RS485: provides 2-way communication - full data
access to user and total instrument confi guration

fully user confi gurable and adjustable over the full
range, full choice of units and sensor fault alarm
functions

Dimensions

Michell Instruments Ltd, Rotronic Instruments Corp. 135 Engineers Road, Suite 150, Hauppauge NY 11788

Tel: [phone], Email: [e-mail], Web: www.michell.com/us

Michell Instruments adopts a continuous development programme which sometimes necessitates specifi cation changes without notice.
Issue no: Cermet II_97169_V2.1_US_0518

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