Xentaur XPDM web Brochure.indd
Model XPDM High-Speed
Portable Dewpoint Meter
Applications:
► Industry Leader in
Electrical Insulating
Gases, SF6 measurements
► Key supplier to largest
Natural Gas
Pipeline System
► Exclusive supplier to
leading Cryogenic and
Specialty Gases producers
► Petrochemical Industry’s
choice for portable measurement
► Recommended by the leading
military research institutes for
Welding and Joining Gases
Measurement
► Aerospace
Accessories:
► Heat treating
Carrying Case
► Medical & Breathing Air
XPDM
Pressure
Regulator
and/or Filter
► LNG, LPG
► Many others
QUICK AND PRECISE SPOT
CHECKS OF MOISTURE
(-148°F to +68°F Dewpoint)
EEx ia IIC T4
Nemko Nr.Ex 99E269
APPROVED
INTRINSICALLY SAFE FOR
CLASS I, DIVISION 1, GROUPS A, B, C, & D
T4 at 40
Xentaur
Overview
Sample Cell Design
The portable Dewpoint Meter Model XPDM is a battery operated,
hand-held instrument, designed for applications where quick and
accurate dewpoint measurements have to be made. With the
XPDM, accurate spot-checks of moisture in gases can be made
faster and easier than ever, over the range of -148°F to +68°F
(-100°C to +20°C) dewpoint.
All surfaces in contact with the sample are made from 316
stainless steel and are electropolished to assure rapid equilibrium
with the sample. Sensor and piston slide through spring-loaded
PTFE seals protecting the sample cell as well as the desiccant
cartridge from intrusion of wet air or gas.
The sample cell can measure gas flows of up to 20 liters per
minute. The flow rate has no effect on the measurement. The
pressure in the sample cell is near atmospheric and should not
exceed 2 bar (29 psi).
The instrument computer gives a read out at sensor pressure
as well as at any line pressure the user enters for the particular
sample. No correction is needed for different gases.
Applications
Important uses of the XPDM include: petrochemical, feedstock
gases, instrument air, transformer and switch gear insulating
gases, gas cylinders and air separation plants, welding gases,
shipboard LNG and aviation oxygen, transfer standard, custody
transfer and others.
Sample Connections
Operating Principle
Aluminum oxide sensors adsorb much faster than they desorb
water molecules. It is therefore an advantage, if at the beginning
of the measurement the sensor is dryer than the sample to be
measured. The XPDM keeps the sensor in dry storage until the
measurement is taken. The sensor slides directly from the dry
storage into the sample cell, without ever coming in contact with
ambient air. After the measurement is completed, the sensor
slides back into the dry storage, where it is dried down for the next
sample.
SENSOR IN
MEASURING POSITION
SENSOR IN DRY
STORAGE POSITION
9
8
Sample connections can be made by means of a variety of different
fittings, depending on the application. The primary port fittings are
1/4” VCO. The following table shows the recommended fittings for
different dewpoint ranges and instrument uses:
Type of
adapter
Range
Remarks
VCO to barbed hose
Used above -85°F (-65°C)
Make sure sample flow
rate is sufficient.
Use PTFE hoses only
VCO to VCO
All ranges
Where flexible connection
is required, use
flexible stainless steel
hoses
VCO to Swagelok
All ranges
Where rigid connections
are acceptable
9
5
2
2
1
1
6
6
3
4
6
5
4
11
6
3
11
7
10
10
1
2
3
4
5
6
Sample Gas IN
Sample Gas OUT
Piston
Sample Cell
Sensor
Spring loaded Teflon Seal
7
8
9
10
11
Sensor Actuator
Desiccant Chamber
Filter Mesh
Electronic Board
Instrument Case
7
Field Exchangeable Desiccant Cartridge
The desiccant cartridge and its connection
to the sample cell have been designed for
maximum gas tightness. The sensor
movement between desiccant chamber
and sample cell occurs with a minimum
amount of gas transfer. Thus, the desiccant
life is prolonged. The desiccant can be
replaced in the field in a matter of minutes,
by simply exchanging the cartridge.
Dry Storage System
The diagram above shows the mechanical design of the XPDM
dry storage sample cell system. The picture on the left shows the
sensor immersed into the desiccant for dry storage. The sensor
is separated from the desiccant by a very fine stainless steel
mesh with a thickness of approximately 5 mil. Close proximity of
the sensor to the desiccant is crucial for fast dry down. With the
sensor in the dry storage position, the sample flows through the
head space between the bottom of the sample cell and the sensor
piston. In order to take a measurement, the gas outlet is blocked
temporarily. The pressure of the sample flow pushes the piston
and pulls the sensor into the sample cell, where it wets up quickly to
the moisture content in the sample flow. An accurate reading can
be taken within 1 to 2 minutes. Afterwards, the sensor is pushed
back into the dry storage position by means of the sensor actuator
which protrudes through the front of the instrument.
Span Check Without Reference Standards
Xentaur HTF™ high capacitance sensors have a very low residual
capacitance when dry, and saturate at a predesigned level of
humidity above +68°F (+20°C). This allows a span check of the
sensor by cupping the sensor in the palm of one’s hand for one
minute, and adjusting the instrument to its upper range limit. The
advantages of this span check system are obvious: Xentaur sensors
can be field calibrated anywhere, anytime without using expensive
and cumbersome calibration standards. Sensors do not have to be
returned to the factory for recalibration, which also eliminates the
need for a second stand-by sensor.
User Interface
The instrument is operated through a simple user
interface consisting of a digital LCD display, and four
push buttons.
The user can select from the following engineering units:
► dewpoint in °C or °F
► ppmv
► lbs H2O/ million scf. (Natural Gas)
► grams of H2O/m3 (Natural Gas)
Results are displayed at sensor pressure
(atmospheric) or by pushing the Pressure Correct key
at a user selectable alternative pressure, such as the
line pressure.
Power Supply and Signal Outputs Option
Faceplate Actual Size
The instrument is powered by a 9V battery which lasts for 100 hours of continuous operation. An automatic shut-off feature
makes sure that the battery is not kept in use unnecessarily.
Optionally, the instrument can be equipped with an external power supply jack and signal output board. The instrument can
then operate from 15 - 20 V AC or DC, or from a car battery adapter. All signal outputs are isolated from the sensor. The
analog output can be current or voltage. The RS-232 output can be easily connected to a PC or a modem.
Xentaur Hyper-Thin-Film (HTF™) Al2O3 Moisture Sensor Technology
The HTF™ aluminum oxide sensor installed in the model
XPDM is the product of years of intensive research at the
laboratories of Xentaur Corporation. It offers significant
performance advantages over all other aluminum oxide
moisture sensors.
The operating
principle is
similar to that of
other aluminum
oxide sensors: a
hygroscopic layer
of aluminum oxide
adsorbs or releases
water molecules within
its pores, depending on the water vapor pressure in its
environment. Thus, the electrical capacitance of the
aluminum oxide layer changes with the surrounding water
vapor pressure. The electrical capacitance is measured
between the aluminum core of the sensor and a porous
conductive gold layer on the outside.
The advantage of the Xentaur sensor is a proprietary
manufacturing method in which the aluminum oxide layer is
made to be hyper-thin as well as extremely hygroscopic. This
results in a very sensitive sensor with fast response.
High Capacitance Response:
Due to the HTF™ Hyper-Thin-Film and a special pore
geometry, Xentaur sensors have a capacitance change over
their full range, several orders of magnitude larger than that
of conventional aluminum oxide sensors. Additionally, this
change is quasi-linear and its sensitivity to temperature is
negligible.
The advantages of a linear high capacitance response are:
better sensitivity, better repeatability and faster response
times. Also, the measurement system is less prone to noise
and drift, and signal conditioning is kept to a minimum.
Technical Specifications
DEWPOINT SENSOR ELEMENT:
Type: . . . . . . . . . . . . . . . . . . . . Hyper-Thin-Film high capacitance Al2O3
Dewpoint range . . . . . . . . . . . . -148°F to +68°F (-100°C to +20°C)
Accuracy: . . . . . . . . . . . . . . . . . ±5.5°F (± 3°C )
Repeatability: . . . . . . . . . . . . . . ±0.9°F (±0.5°C)
Response time*: . . . . . . . . . . . For a step change from -40°C to -60°C: 63% in 90 seconds; 90% in 450 seconds
TEMPERATURE RANGE:
Sensor: . . . . . . . . . . . . . . . . . . . -22°F to 120°F (-30°C to +50°C)
Electronics: . . . . . . . . . . . . . . . . 14°F to 120°F (-10°C to +50°C)
Storage temperature: . . . . . . -4°F to +140°F (-20°C to +60°C)
Sample flow range: . . . . . . . . . Static to 100 m/s(linear velocity @1atm)
Calibration method: . . . . . . . . This field calibration procedure is fully automated and the user is prompted though a simple one minute
procedure, which requires no additional equipment. NIST traceable factory calibration optionally available.
TEMPERATURE AND PRESSURE MEASUREMENTS:
The sample temperature is measured with a precision integrated circuit temperature sensor.
Units may be optionally fitted with a pressure sensor.
MECHANICAL :
Enclosure . . . . . . . . . . . . . . . . .
Sampling chamber . . . . . . . . .
Moving parts seals: . . . . . . . .
Pressure operating range: . .
Anodized Aluminum, Dimensions: 2.5“ x 4.25” x 7.5”. Regulator and Filter mounting facilities.
Electropolished 316 stainless steel
Spring energized PTFE seals
Standard: 29 PSI (2 bar)
Absolute max.: 100 PSI (6.8 bar)
Gas sample connections: . . . 1/4” VCO input and output ports
Electrical connections: . . . . . . Optional 2mm DC power jack, 9 pin “D” for analog & RS-232.
Power requirements: . . . . . . . 9v battery and optional 15-25V AC or DC wall transformer.
* These response times are not directly comparable to competitors data, because of differences in measurement methodology and
data presentation. Please inquire for detailed comparisons between Xentaur and other major sensor manufacturers.
FEATURES:
Sensor storage: . . . . . . . . . . . . When not in use the sensor is retracted in a molecular sieve container and kept at an approximate
dewpoint of -80°C. The sample gas pressure activates a piston which automatically moves the sensor
into the sampling chamber, thus even low dewpoints can be measured extremely quickly.
Area classification . . . . . . . . . . Approved for use in hazardous (classified) areas Class I, Div. 1, Groups A, B, C & D. Available as an option.
Input resolution: . . . . . . . . . . . . 0.1°C dew point.
Indicators: . . . . . . . . . . . . . . . . . LCD with backlight, 3.5 digits and custom legends for units and mode, audio alert.
Engineering units: . . . . . . . . . . °C,°F, PPM, lbs.H2O/mm scf, gm.H20/m3
Controls: . . . . . . . . . . . . . . . . . . 5 push buttons, all settings stored in EEprom. Manual Sensor Actuator.
Outputs: . . . . . . . . . . . . . . . . . . . Optional 4/20mA or 0/24mA and RS-232.
Isolation: . . . . . . . . . . . . . . . . . . Sensor and case are isolated from the power supply , analog output and RS-232.
Battery saver: . . . . . . . . . . . . . Auto power off after 6 minutes.
Pressure correct: . . . . . . . . . . Programmable pressure correction button.
For more detailed technical comparisons
with other technologies visit:
http://www.xentaur.com
Xentaur
84F Horseblock Rd
Yaphank, NY 11980
Tel 631.345.3434
Fax 631.345.5349
E-mail: xentaur@xentaur.com, www.xentaur.com
REPRESENTED BY:
rev 103.1
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