GE M Operating Manual

GE

Sensing

M Series

Panametrics Aluminum
Oxide Moisture Probe

M Series probe is a Panametrics
product. Panametrics has joined
other GE high-technology sensing
businesses under a new name

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GE Industrial, Sensing.

This Panametrics aluminum oxide moisture sensor probe
measures moisture concentration in gases and
non-aqueous liquids from trace to ambient levels. It is
designed to be used in conjunction with all Panametrics
moisture analyzers for industries including:

• Petrochemical

• Natural gas

• Industrial gas

• Semiconductor

• Furnace gas/heat treating

• Power generation

• Air dryer

• Pharmaceutical

• Aerospace

Applications

Features

• Intrinsically safe when used in conjunction with
certified electronics or zener barriers

• Superior sensitivity, response speed and calibration
stability

• Optional temperature sensor

• Calibrations traceable to National Institute of
Standards and Technology (NIST) or National
Physical Lab U.K. (NPL)

• Designed for in situ applications or in conjunction with
sample conditioning systems

• True absolute humidity sensor

• Wide dynamic range

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GE

Sensing

Panametrics Hygrometer Systems
and Moisture Probes

Panametrics aluminum oxide moisture probes have set
the standard of performance and value in industrial
moisture measurement for more than 40 years.

In use, M Series moisture probes are coupled to
Panametrics hygrometer consoles by an interconnecting
cable. Ease of use, wide measurement range and
rigorous calibration standards make these systems the
preferred choice for industrial moisture measurement
worldwide.

Superior Performance

Film thickness of the oxide layer is critical to the
performance of this type of sensor. GE manufactures
sensors with an oxide film thickness that causes them to
exhibit true absolute humidity, rather than relative
humidity response. This critical film thickness also gives
the M Series probe quick response and exceptional
calibration stability.

Rigorous Calibration Standards
Traceable to NIST/NPL

Each Panametrics aluminum oxide sensor is individually
calibrated in one of the world’s most advanced moisture
calibration facilities. Developed over several decades,
this facility uses flow, temperature and pressure
measuring devices, traceable to NIST/NPL, to generate
precisely known moisture concentrations to which each
probe is exposed during the calibration process.

All data is gathered and stored by a dedicated computer
system. Calibrations are repeated over a period of
months to determine the stability of each individual
moisture probe. Only those probes that meet GE’s
demanding specifications for accuracy and stability are
shipped to customers.

Theory of Operation in Gases and
Liquids

The direct measurement of water vapor pressure is
accomplished easily and effectively in both gases and
liquids by the M Series aluminum oxide moisture sensor.
The sensor consists of an aluminum strip that is
anodized by a special process to provide a porous oxide
layer over which a very thin coating of gold is
evaporated. The aluminum base and the gold layer form
the two electrodes of what is essentially an aluminum
oxide capacitor.

Water vapor is rapidly transported through the gold
layer and equilibrates on the pore walls of the oxide
layer. The number of water molecules absorbed on the
oxide structure determines the conductivity of the pore
walls. Each value of pore wall resistance provides a
distinct value of electrical impedance, which in turn is
functionally related to the water vapor pressure. This
functional relationship holds for measurements made in
either gas phase or liquid phase.

Installation Flexibility

M Series probes are designed to be located at the
process, exactly where the measurement is needed.
Cable length between the probe and hygrometer may
be 2000 ft (610 m) or more. Operating temperature
range is –166°F to 158°F (–110°C to 70°C), pressure
range is from vacuum up to 5000 psig (345 bar), and no
minimum flow rate is required. Sample cells make
M Series probes easy to install, and the cells are
available in general purpose, Type 4 weatherproof, and
Type 7 explosion-proof housings.

Remote installation of the probe and wide operating
parameters allow for in situ placement of the probe.
Because a sample need not be brought to the analyzer,
both the time lag and the potential for sample
contamination associated with sample delivery systems
are eliminated. This feature is extremely important in the
measurement of very low moisture content or where
rapid changes occur.

When the integrity of the measurement is threatened by
conductive or erosive particles, or adverse process
conditions, sample conditioning will be required. GE
manufactures turnkey sample-conditioning systems that
maintain the integrity of the sample’s moisture content
while removing the contaminants. These designs have
been field-tested and have proven to be reliable, while
requiring little or no maintenance.