A full specification on-line hygrometer for the measurement of dew point in air and process
gases, with wide operating range and multiple display options.
Wide measurement range, calibrated -100 to +20°Cdp
±1°Cdp measurement accuracy
Pressure sensor input
Up to 4 alarm relays
User selectable units of measurement
Easy to read display
Analog and digital outputs
Dried compressed air
High voltage switchgear (SF6)
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. 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 dew point at pressures up
to 400 barg. 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
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.
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 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. From -100 to -60°C
dew point the measurement accuracy is ±2°C 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.
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.
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.
Impedance - The Cermet II 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
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.