Phymetrix PLMa User manual

PhyMetrix Loop-powered Moisture analyzer
User's Manual for Models PLMa and PLMaEx

Read this manual before using the analyzer. For personal and system safety, and for
optimum product performance, make sure you thoroughly understand the contents
before installing, using, or maintaining this analyzer.
Please visit our website at www.phymetrix.com for other products that may be applicable to your
needs.
Every effort has been made to ensure accuracy in the contents of this manual. Should there be
any doubts to the accuracy of the content please contact the manufacturer.
The contents of this manual are subject to change without notice.
The instructions, procedures, drawings, specifications and concepts contained in this manual are
the property of Phymetrix Inc., and shall not be used as the basis for the manufacture or sale of
apparatus or services, or reproduced or copied or transmitted in any form or by any means
without written permission.

Warranty
This instrument is warranted, to the original end-user purchaser, against defects in materials and
workmanship. Liability under this warranty is limited to restoring the instrument to normal
operation or replacing the analyzer, at the sole discretion of the manufacturer. This warranty is
effective from the date of delivery to the original purchaser. If Phymetrix determines that the
equipment was defective, the warranty period is:
• one year from delivery for electronic or mechanical failures
• one year from delivery for sensor shelf life
If Phymetrix determines that the equipment was damaged by misuse, improper installation, the
use of unauthorized replacement parts, or operating conditions outside the guidelines specified,
the repairs are not covered under this warranty.
Normal wear and tear, parts damaged by abuse, misuse, negligence or accidents are specifically
excluded from the warranty.
Purchaser acknowledges that in accepting and using this analyzer, notwithstanding any contrary
term or provision in the purchaser's purchase order or otherwise, the only warranty extended by
Phymetrix is the express warranty contained herein. Purchaser further acknowledges that there
are no other warranties expressed or implied, including without limitation, the warranty of
merchantability or fitness for a particular purpose; that there are no warranties which extend
beyond the description of the face hereof; that no oral warranties, representations, or guarantees
of any kind have been made by Phymetrix, its distributors or the agents of either of them, that in
any way alter the terms of this warranty; that Phymetrix and its distributors shall in no event be
liable for any consequential or incidental damages, including but not limited to injury to the
person or property of the purchaser or others, and from other losses or expenses incurred by the
purchaser arising from the use, operation, storage or maintenance of the product covered by the
warranty; that Phymetrix’s liability under this warranty is restricted to repair or replacement of
defective parts at Phymetrix sole option; and that Phymetrix neither assumes nor authorizes any
other person to assume for it any other warranty. The warranty shall be void if serial numbers
affixed to the products are removed, obliterated or defaced.
Return Policy / Procedures
If equipment malfunction is suspected or it is determined that the analyzer needs recalibration,
please contact Phymetrix.
Communicate the instrument model number, serial number, application including dewpoint
range being measured, and the details of the problem.
If the analyzer needs factory service you will be issued a RMA and shipping instructions.
The factory will diagnose the equipment and upon determining the problem will notify you
whether the terms of the warranty cover the required repair. If the costs are not covered you will
need to approve the estimated cost in order to proceed with the repair.

Table Of Contents
1 Introduction............................................................................................................................. 1
2 Important Principles of Operation .......................................................................................... 2
2.1 Sensor Operating Principle ............................................................................................. 2
2.2 Sampling Mechanism Operating Principle ..................................................................... 2
3 Precautions ................................................................................................................ 3
4 Moisture System Considerations ............................................................................................ 4
4.1 Integrity of the Materials of the User’s System.............................................................. 4
4.2 Moisture Back Diffusion (backflow) Along the Walls of the Exhaust Tubing .............. 4
4.3 Temperature Dependant Equilibrium ............................................................................. 5
5 Sampling Techniques.............................................................................................................. 5
5.1 Choosing a Measurement Site ........................................................................................ 5
5.2 Sample Conditioning ...................................................................................................... 5
5.3 Tubing and Fittings .........................................................................................................6
5.4 Sample Pressure.............................................................................................................. 6
5.5 Pressure Considerations.................................................................................................. 7
6 Installation............................................................................................................................... 8
6.1 Mechanical Installation................................................................................................... 8
6.1.1 PLMa Mechanical Installation................................................................................ 8
6.1.2 PLMaEx Mechanical Installation ........................................................................... 8
6.1.3 PLMa-Probe-Ex Mechanical Installation ............................................................... 8
6.2 Electrical Connections: Power, 4/20mA Analog Output, Serial I/O .............................. 8
6.2.1 Powering the PLMa , PLMaEx or PLMa-Probe-Ex ............................................... 8
6.2.2 Serial I/O RS-232.................................................................................................... 9
7 Digital Interface - HART ........................................................................................................ 9
8 Troubleshooting and Maintenance........................................................................................ 11
8.1 Cleaning ........................................................................................................................ 11
8.2 Self Diagnostics ............................................................................................................ 11
8.3 Suspected Erroneous Measurements............................................................................. 11
9 Specifications........................................................................................................................ 13
9.1 Model PLMa ................................................................................................................. 13
9.2 Model PLMaEx and PLMa-Probe-Ex .......................................................................... 13
Appendix A PLMa Installation Drawing............................................................................... 14
Appendix B PLMaEx Installation Drawing .......................................................................... 16
Appendix C PLMa Probe Ex Installation Drawing............................................................... 17
Appendix D Dewpoint Display ................................................................................................ 19
Appendix E Analyzer Calibration Log .................................................................................... 23
Revision #2.1 August 2013

Revision #2.1 August 2013
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1Introduction
Thank you for purchasing the state-of-the-art Phymetrix Loop-powered Moisture Analyzer
model PLMa or PLMaEx or PLMa-Probe-Ex.
These analyzers measure moisture content in gasses in the range -110°Cdp to +20°Cdp and
provide a 4-20mA output linear to the measurement units chosen. The factory default is
4mA= -100°Cdp and 20mA= +20°Cdp. Using the HART interface the defaults can be modified
in value and units (available units: °C & °F dewpoint, ppmV, ppmW, mB H2O vapor pressure,
grams of H2O / m3and Lbs H2O /106standard cubic feet in Natural Gas ). The PLMa is a Loop-
Powered Blind (two wire) Transmitter; thus it has no display and the 4-20mA output is
transmitted on the two power pins by consuming power in the range of 4mA to 20mA. In
addition the PLMa is equipped with a HART interface which superimposes a digital
communications signal on the 4-20mA loop.
This User’s Manual describes the functions of these analyzers as well as the operating methods
and handling precautions. There are also some sections that review general knowledge and
concepts of water vapor science. Read this manual thoroughly before using the analyzer. There is
a Quick Setup Manual describing the main functions and basic procedures for performing
measuring operations. Check our website “www.phymetrix.com” for latest versions of
documentation regarding these analyzers.
After reading this manual, keep it easily accessible for future reference. It may come in handy
when there are some challenging measurements to be performed.
Conventions used in this manual:
When using the word “system” in this manual we are referring to the user’s system in which
the moisture content is being measured. This could be a simple configuration of a pressurized
gas bottle with a pressure regulator, or a complex system of dryers, filters, regulators, long
tubing/pipes, valves etc.
Check to see that your analyzer has arrived intact with all accessories.
Models: PLMa & cable OR PLMaEx OR PLMa-Probe-Ex
Save the packing materials at least until you have verified that there is no concealed damage, it
may also be useful for future transportation.
1

2Important Principles of Operation
2.1 Sensor Operating Principle
The nanopore sensor utilized in this analyzer measures the amount of water vapor molecules that
have entered its pores. This amount is directly proportional to the partial water vapor pressure in
the gas surrounding the sensor, and the partial water vapor pressure is dependant on the water
vapor content of the gas and the total pressure of the gas. Thus to compute the water vapor
content of the gas under measurement the analyzer has to “know” the total pressure of the gas.
Since there is no built-in pressure sensor, the user should enter the total pressure into the
analyzer, this can be easily done by entering atmospheric pressure (the analyzer default setting)
and measuring at atmospheric pressure by allowing the sample cell outlet (exhaust) port to vent
without restrictions.
2.2 Sampling Mechanism Operating Principle
The PLMa is intended to be installed in the user’s system or in a sample cell. The PLMa is
provided with 3/4”-16 parallel treads with O-ring seal, and with 1/4” Male NPT threads. See
Appendix A.
The PLMaEx is equipped with a built-in sampling system which has the required tight seals to
measure low moisture content; it consists of a stainless steel 100 micron filter and a flow control
orifice (which may be placed at either the inlet or outlet of the sampling cell or removed). The
gas under measurement is exposed only to the stainless steel walls of the sampling system. See
Appendix B.
The PLMa-Probe-Ex is the first and only moisture analyzer probe designed to directly insert
into a “live” pressurized pipeline, thus avoiding the need to shut down the pipeline when
inserting or removing for re-calibration or pipeline service. It has an all stainless steel
construction, is small enough to be installed on a 1/2” or larger Ball Valve, seals with
3/8“ Swagelok tube fittings and has sufficient travel for insertion even into the largest diameter
pipelines.
The Phymetrix PLMa-Probe-Ex meets the new environmental requirements of not exhausting
gas while making a measurement at a lower cost than an extractive sample system.
2

3Precautions
Observe the appropriate electrical safety codes and regulations. Consult with National
Electrical Code, and/or other nationally or locally recognized procedures relevant to your
location.
When measuring flammable, explosive or toxic gasses; vent the sample outlet to a safe
and appropriate location.
When measuring high pressure samples (do not exceed 1000 psia); be sure that the
system is depressurized before connecting or disconnecting the sample tubing.
Corrosives such as Ammonia, HCl and Chlorine should be avoided; H2S and SO2can be
present if the moisture content is below 10 PPMv.
Avoid extreme temperatures, pressures and mechanical vibration, refer to specifications.
Do not disassemble the analyzer.
Do not use with contaminants and liquids, refer to section 5.2 for sample conditioning.
Avoid exposing the sensor to ambient air as it may slowdown your next measurement.
The PLMa and its I/O connector are weatherproof.
Save the shipping Tube to be used if the PLMa needs to be shipped for recalibration.
3

4Moisture System Considerations
This section is offered as background information. There are several considerations in keeping
your system at a stable and pure moisture level, free of contamination from ambient air moisture:
The integrity of the materials isolating the pure gas from the external air, including leaks
from poorly secured fittings.
The back diffusion of moisture through the exhaust outlet, the exhausts of both the
analyzer and the user system under measurement should be considered.
The effects of temperature on the equilibrium of moisture and the surrounding materials,
often observed as diurnal cycles in the measurement.
4.1 Integrity of the Materials of the User’s System
Before considering the materials of a system where a specified dewpoint level must be
maintained, one should review two concepts.
Compared to the structure of solids the water molecule is much smaller. This is true
compared to even the crystalline structure of metals but especially important in the
polymer structure of plastics.
Water vapor pressure in gasses obeys Dalton’s law of partial pressures, which states that
the overall pressure of a gas is the sum of its constituent gases. And each gas seeks to
equilibrate its pressure across gradients of only its own gas pressure.
Let’s consider air in a pipe at a total pressure of 100 psia, which has been dried down to -40°C
dewpoint. The partial water vapor pressure in the pipe is 0.13mB. If the ambient temperature is
22°C with relative humidity of 30%, then the partial water vapor pressure in the surrounding
atmosphere is 7.9mB or approximately 60 times greater than the partial water vapor pressure in
the pipe. Thus even though the total pressure in the pipe is much greater that the pressure outside,
the reverse is true for the water vapor pressure, and as we discussed earlier the water vapor seeks
to equilibrate its pressure thus it “wants” to flow from the outside to the inside and will do so
through the cracks in the joints (such as poorly tightened fittings, or NPT threads even if they are
properly taped), as well as through the walls of pipes tubes and other vessels. The integrity of the
system is extremely important in maintaining a stable low dewpoint; for dewpoints below -60°C
always use stainless steel or PTFE, while for higher dewpoints you can use copper or galvanized
steel; but never use rubber, Tygon, Nylon or other plastic tubing. Pressure regulators often use
rubber diaphragms, check and if necessary replace with a stainless steel diaphragm regulator.
Filter bowls should be stainless steel or glass, plastic bowls should be avoided. If a flow meter is
placed at the inlet of the analyzer it should have a glass tube and be rated for the expected
pressure levels, however in general it is best to place flow meters at the analyzer exhaust.
Another material consideration relates to materials sealed in the system such as paper filters;
these may not contribute to leaks but will greatly slow down the measurement because they will
adsorb and desorb water molecules as the system dewpoint is changing.
4.2 Moisture Back Diffusion (backflow) Along the Walls of the Exhaust Tubing
The linear velocity of gas flowing in a tube is close to zero immediately along the wall of the
tube. This coupled with the previously discussed “need” for the moisture to flow from the higher
water vapor pressure to the lower one, allows for water molecules to flow against the flow
through the exhaust outlet into the sampling chamber of the analyzer. The fact that water
4

molecules are highly polar further enhances their ability to migrate against the gas flow at the
sampling chamber outlet. To prevent this backflow of moisture from influencing the
measurement, the analyzer should have at least 12” in length of 1/8” dia. stainless steel tubing at
its exhaust port, and a minimum flow of 2 SCFH (1 SLPM) should be maintained; higher flows
will produce faster equilibrium time and thus are desirable for quick measuring. A small pigtail
(coiled 1/8” dia. ss. tubing 12” long) can be connected to the exhaust port of the analyzer.
Alternatively a short tube with attached flow meter can also provide protection from back
diffusion of moisture.
4.3 Temperature Dependant Equilibrium
The effect of ambient temperature on the gas partial water vapor pressure of a system can change
the moisture content of the gas. This is not the temperature sensitivity of the measuring analyzer,
rather the actual change of partial water vapor pressure in the user’s system due to increase in
ambient temperature and thus the increase of energy of the water molecules on and in the walls
of the system (tubing, vessels etc…). A typical example would be the observation of a daily
cycling of the measurement in a system with tubing or other components exposed to direct
sunlight. During the day as the sun transfers energy into the system, the dewpoint will appear to
increase, while at night the dewpoint will appear to decrease. There may be other reasons for this
daily dewpoint cycling such as the effect of sun/temperature on the efficiency of gas dryers etc.
It is possible to minimize this effect using sun shields and tubing insulators. Alternatively one
may study the response of the particular system to ambient temperature, by logging data over
several days during different seasons, and compensating the measurements for this effect. The
temperature effect will vary greatly depending on the size and materials of the system, for
example stainless steel walls will have a much smaller effect than brass or copper walls.
5Sampling Techniques
The amount of moisture measured will be influenced by the system moisture content as well as
leaks in the system and transient effects of adsorption / desorption from materials in the system
(as described in the previous sections).
5.1 Choosing a Measurement Site
The PLMa has been designed to perform extractive or in-situ measurements. The PLMaEx is
designed for extractive measurements only. The PLMa-Probe-Ex is designed mainly for in-situ
measurements. It is important to choose an appropriate sampling location that is representative of
the moisture content of the system of interest. If you feel you need assistance, please call our
application engineers.
5.2 Sample Conditioning
Particulate and liquid contaminants can effect the measurement, especially the response time.
Sample conditioning may be necessary to remove contaminants and improve the measurement
and the longevity of the sensor. Make sure that sample conditioning components are made of
suitable materials. Avoid paper or other fiber filter elements, use stainless steel instead. For
expected dewpoints below -50°Cdp (39 PPMv), avoid plastic filter bowls, use stainless steel or
glass instead. Drain trapped liquids from filter bowls.
5

If the application is suspect of possible presence of liquids for example:
• Compressed air with possible oil and/or water,
• Gas Insulated Switchgear or Transformer, SF6or N2blanket with suspected oil carryover,
• Natural Gas with possible Triethylene Glycol carryover,
Consult with Phymetrix for specialized sampling systems.
5.3 Tubing and Fittings
Make sure all tubing is constructed of materials suitable for low dewpoint measurement, i.e.
stainless steel or Teflon, do not use rubber or plastic tubing (refer to section 4.1 for more details).
Check for leaks after connecting.
Flow meters can be a source of moisture ingress especially if they have a plastic flow tube;
ensure flow meters are connected at the analyzer exhaust, not at inlet. However metering valves
should be at the inlet in order to maintain constant atmospheric pressure in the sampling chamber.
5.4 Sample Pressure
Pressure variations will effect the measurement. Higher pressure is more likely to produce
condensation and thus erroneous readings or even damage the sensor. If the sample pressure
needs to be reduced use a suitable pressure dropping device such as a stainless steel needle valve
or pressure regulator with a stainless steel diaphragm or a flow control orifice. Make sure Joule-
Thomson effects do not cool the gas below hydrocarbon and water dewpoints.
Exhaust
Main Pipe
Flow
Metering Valve
or
Pressure Regulator
Sample Cell
Sample pickup
away from walls
PLMa
Install this
side UP
6

5.5 Pressure Considerations
When sampling gases from sources above 50 psia the user needs to exercise some caution.
The model PLMaEx has a built-in orifice. This orifice can be used to regulate the flow from
various pressures.
PLMaEx Measuring near Atmospheric Pressure PLMaEx Measuring at Pressure of Sample Gas
The inlet orifice eliminates the need for any pressure regulators while maintaining sufficient but
not excessive flows throughout the pressure rating of the analyzer. For example 0.004” to 0.016”
dia. orifices, produces flows described in the following table.
The grayed boxes are preferred operating points. Other orifices can be provided to accommodate
different pressures and flows. Consult PhyMetrix support for its proper sizing.
source pressure
psia - (Bar)
flow
SLPM
0.016” orifice
flow
SLPM
0.012” orifice)
flow
SLPM
0.008” orifice
flow
SLPM
0.006” orifice
flow
SLPM
0.004” orifice
15 - (1.03) 0.7 0.4 0.17 0.08 0.04
25 - (1.72) 2 1.3 0.6 0.3 0.1
35 - (2.4) 3 1.9 0.8 0.5 0.2
55 - (3.8) 4.8 3.0 1.4 0.7 0.3
75 - (5.2) 6.6 4.1 1.9 1.0 0.4
100 - (6.9) 8.9 5.5 2.6 1.4 0.6
150 - (10.3) 13.4 8.3 3.8 2.1 0.9
200 - (13.8) 17.9 11.0 5.1 2.7 1.1
300 - (20.7) 26.8 16.6 7.7 4.1 1.7
400 - (27.6) 35.7 22.1 10.3 5.5 2.3
500 - (34.5) 44.7 27.6 12.8 6.9 2.9
600 - (41.4) 53.6 33.1 15.4 8.2 3.4
700 - (48.3) 62.5 38.7 18.0 9.6 4.0
800 - (55.1) 71.5 44.2 20.5 11.0 4.6
900 - (62) 80.4 49.7 23.1 12.4 5.1
1000 - (68.9) 89.3 55.2 25.7 13.7 5.7
1500 - (103.4) 134.0 82.8 38.5 20.6 8.6
2000 - (137.9) 178.7 110.5 51.3 27.5 11.4
7

Measuring with the PLMaEx, Near Atmospheric Pressure
It is recommended for most applications to perform the measurement at near atmospheric
pressure. Placing the flow control orifice at the inlet and allowing the outlet to be unrestricted
(other than the exhaust pigtail and flow meter), assures that the analyzer has sufficient but not
excessive flow and the pressure inside the sampling chamber is near atmospheric. This approach
guarantees safe conditions and eliminates the need for the optional pressure sensor. If there is no
pressure sensor the analyzer can be set with atmospheric pressure 14.7psia for the Measuring
setting of the pressure correction (refer to section factory default setting, the orifice and
unrestricted outlet will guarantee repeatable conditions for all pressures within the rating of the
orifice.
Measuring with the PLMaEx, at Pressure of Sample
If it is desired to perform the measurement at the same pressure as the sample, up to the rating of
the analyzer (1000 psia standard), then place the orifice at the outlet.
When the analyzer is setup with the orifice at the outlet, the measuring chamber will be
pressurized to the same pressure as your sample. To perform accurate measurements, you must
know the pressure and enter it into the analyzer.
6Installation
6.1 Mechanical Installation
6.1.1 PLMa Mechanical Installation
The PLMa can be mounted directly on a sample cell or any vessel equipped with 3/4"-16 parallel
threads port or 1/4 NPT pipe threads. Refer to Appendix A PLMa Installation Drawing.
6.1.2 PLMaEx Mechanical Installation
The PLMaEx can be mounted directly on the pipe or can be mounted on a panel surface and
connected with tubing. Refer to Appendix B PLMaEx Installation Drawing.
Connections for inlet and outlet of the gas being measured are made through a variety of
available options e.g. ⅛” or ¼” Swagelok® tubing compression fittings.
Refer to Mechanical Installation Drawing Appendix B.
6.1.3 PLMa-Probe-Ex Mechanical Installation
The PLMa-Probe-Ex is intended to be installed directly on the pipeline through a 1/2" or larger
ball valve. Refer to Mechanical Installation Drawing and pictorial Installation Instructions in
Appendix C.
6.2 Electrical Connections: Power, 4/20mA Analog Output, Serial I/O
6.2.1 Powering the PLMa , PLMaEx or PLMa-Probe-Ex
The PLMa, PLMaEx and PLMa-Probe-Ex are 4/20mA loop powered analyzers with a HART
digital interface. The analyzer will operate from 5 VDC to 28VDC power and will draw 4mA to
8

20mA depending on the measurement and the analog output settings (factory default 4mA=-
100°C and 20mA=+20°C).
Refer to the PLMa Electrical Connection diagram in Appendix A, for specific wiring
connections.
The PLMa is equipped with a male M12 connector, which mates to all standard M12 connectors.
The PLMa is supplied with a 3 meter cable with a molded right angle connector. The M12
connector on the PLMa and on the cable are weatherproof.
The PLMaEx and PLMa-Probe-Ex have a explosion proof junction box with pluggable screw
terminal connector. Conduit can be connected to the junction boxes 3/4" NPT port.
6.2.2 Serial I/O RS-232
The PLMa can provide a RS-232 interface. Refer to the PLMa Electrical Connection diagram
in Appendix A for connections.
7Digital Interface - HART
The PLMa is equipped with a HART interface which overlays digital signals on the 4-20mA
loop current. Thus the PLMa can be used in any 4-20mA loop and can simultaneously
communicate digitally on the same two wires.
The PLMa responds to all of the HART Universal (Common Practice) Commands as well as
some important setup and configuration commands.
9

HART Commands Implemented in the PLMa, PLMaEx and PLMa-Probe-Ex
HART Command
# Name
Description
0 Read Unique Identifier Read Device identification such as address, manufacturer, revision
level etc.
1 Read Primary Variable Read the measurement of the Primary Variable (P.V.)
2 Read Current and % of range Read the current that is produced by the Primary Variable and the
percent of range it represents. These depend on the command #51
measurement assigned to the P.V., the value of that measurement and
the assignments of command #35.
3 Read Dynamic Variables and
P.V. current
Read the measurements of up to 4 measurement variables as assigned
by command # 51.
6 Write Polling Address Assign a polling address to a device. An address (1-15) puts the
device in fixed 4mA mode for multidrop connectivity. Address 0 puts
the device in 4/20mA mode.
11 Read Unique Identifier
Associated with Tag
Find device that has the desired textual Tag assigned by
command # 18.
12 Read Message Read information written by command # 17.
13 Read Tag, Descriptor and Date Read information written by command # 18.
14 Read P.V. Sensor Information Information on primary sensor Serial Number, range etc.
15 Read P.V. Output Setup Analog output range, alarms etc.
16 Read Final Assembly Number Read number written by command # 19.
17 Write Message For use by owner/operator to identify the device and its use.
18 Write Tag, Descriptor and Date For use by owner/operator to identify the device and its use. Can
search for the Tag, with command # 11, on multidrop connections.
19 Write Final Assembly Number For use by owner/operator to identify the device and its use.
35 Write Primary Variable
Range Values
Setup the measurement units and values that correspond to 4mA and
20mA output of the loop.
40 Analog Out Fixed Forces the Analog Output DAC to a specified value.
44 Write Primary Variable Units Select the units of measure for the Primary Variable.
45 Trim DAC Zero Trims the DAC Zero by difference of Cmnd. #40 and observed value.
46 Trim DAC Gain Trims the DAC Gain by ratio of Cmnd. #40 and observed value.
50 Read Dynamic Variable
Assignments
Read the assignments of
command # 51.
51 Write Dynamic Variable
Assignments
Assign Measurement
Variables to each of the four
primary variables reported by
the analyzer by command # 3.
53 Write Transmitter Variable
Units
Select Units of measure for
each of the Variables.
Measurement Variables and [available units]:
00 – Moisture Measurement
°C & °F dewpoint, ppmV, mB H2O vapor pressure,
grams of H2O / m3and
Lbs H2O /106standard cubic feet in Natural Gas
01 – Temperature of Gas [ °C, °F ]
02 – Temperature of Board [ °C, °F ]
03 – Pressure [ psi, bar, mbar, kg/sqcm, pascal …]
08 – Loop Voltage [ mV ]
09 – Status Bits
108 Write Burst Command Number Select command number to burst.
109 Burst Mode Control Enable/Disable burst (continuous) transmissions.
A free of charge program may be downloaded from our website www.phymetrix.com/hart.htm
that allows communicating with the PLMa or PLMaEx or PLMa-Probe-Ex HART interface.
10

11
8Troubleshooting and Maintenance
This analyzer is designed to be maintenance and trouble free. However should problems occur
due to process conditions or other factors, use this chapter for troubleshooting purposes. If the
encountered circumstances are not discussed in this manual please contact Phymetrix. Spare
parts may be ordered through Phymetrix.
8.1 Cleaning
The analyzer enclosure may be cleaned using a moist cloth.
The flow control orifice of the PLMaEx can be removed and cleaned with solvents.
The sensor is not user serviceable and should not be cleaned by the user. If it is contaminated
please acquire an RMA and send the analyzer for repair.
8.2 Self Diagnostics
The analyzer constantly performs self diagnostics to determine if all parts are operating properly.
The results of the diagnostics are communicated based on the alarm selection settings of HART
command #15. The factory default is that a fault will cause the current to go to its high value
(20mA).
8.3 Suspected Erroneous Measurements
Some of the most common suspected erroneous conditions are listed in the following table
included are common reasons and suggested remedies.
If the measurement is suspected to be erroneous, before calling for support, it may be helpful to
have the following information:
Type of gas being measured.
Expected dewpoint.
Nominal pressure (consider back pressure).
Nominal temperature.
Nominal flow rate though the analyzer.
Flow diagram or description of system, showing items and their materials of construction.
Include materials of filer elements, regulator diaphragms, and valve seats.
Possible contaminants (particulates, liquids, oil, glycol, cleaning solutions, etc.).
Are the pipes and analyzer purged before measuring? How long? Flow rate? With the
same gas that will be measured?
If other equipment was used to verify the dewpoint, what is the equipment (include
model number)? What is its specified measuring range? When was it last
calibrated/certified?
If using bottled gas for reference: Manufacturer? Content and accuracy markings? What
is the pressure in the bottle at time of comparison? What is the ambient temperature
where the bottle is stored? What are the materials of construction of the pressure
regulator, especially the diaphragm?

Table 2 Guide to Troubleshooting Measurements
Problem or Unexpected
Observation Behavior Likely Source of Problem Analysis Remedy
Equilibrium Before concluding that there is an incorrect measurement, make sure that
the system is at equilibrium.
Graph the measurements and wait for
equilibrium.
Sampling point Consider if the sampling point could be dryer than the rest of the system. If necessary find a more appropriate sample point
Damage
Corrosion, abrasion
Contaminants can damage the sensor. Refer to sections: 3Precautions and 5.2 Sample
conditioning.
Measurement is dryer than
is expected.
Needs recalibration Depending on the application recalibration may be yearly or in 5 years. Consult with factory.
Equilibrium Before concluding that there is an incorrect measurement, make sure that
the system is at equilibrium.
Graph the measurements and wait for
equilibrium.
Sampling point Consider if the sampling point could be wetter than the rest of the system. If necessary find a more appropriate sample point
Condensation Refer to the “Measurement is not changing” observation below
Damage
Corrosion, abrasion
Contaminants can damage the sensor. Refer to sections: 3Precautions and 5.2 Sample
conditioning.
Incompatible materials in system
with low dewpoint.
Refer to section 4.1 Integrity of the materials of the system. Replace inappropriate materials.
Leaks Check for leaks around all interconnections. Tighten fittings. Repair the leaks.
Measurement is wetter than
is expected.
Needs recalibration Depending on the application recalibration may be yearly or in 5 years. Consult with factory.
Equilibrium The rate at which the system will reach equilibrium depends on the system
particulars, such at ambient temperature, internal pressure, flow rates,
system materials of construction, surface area of system internals.
Previous experience may be indicative of the
system response time. It is common for systems
to take hours to equilibrate.
Sampling point Is the sampling point in the direct flow of the system gas, or is it at a dead
end of the distribution system?
Sample in the direct flow.
Contamination Are there hygroscopic contaminants? Clean the sensor and install filters.
Out-gassing Are there materials in the system that could be out-gassing? Replace the hygroscopic materials.
Leaks Check for leaks around all interconnections. Tighten fittings. Repair the leaks.
Large diameter sampling tubing Larger diameter tubing have larger surfaces. Use smallest practical tubing diameter, 1/8”
recommended
Measurement is changing
slower than expected.
Low flow rate Response time is normally greatly influenced by flow rate, but if the
measurement value is influenced by flow rate there may be a leak.
Flow rate should be greater than
1 LPM.
Measurement is not
changing, always shows a
dewpoint close to ambient
temperature.
Condensation Condensation may have occurred from a slug of water or from previous
conditions where the gas dewpoint was greater than the ambient
temperature. Condensation typically accumulates in filter bowls or other
low points in the system. Then evaporates and produces a high dewpoint.
Drain the condensate and allow the system to dry
down.
Measurement has a daily
cycle
Thermally induced water vapor
pressure change.
Refer to section 4.3 Temperature dependant equilibrium
12

9Specifications
9.1 Model PLMa
Temperature
Range
PLMa Analyzer: -20°C to +60°C
Electronics: -40°C to +85°C
Moisture Sensor: -20°C to +60°C
Moisture
Sensor
Range -110°C to +20°C
Accuracy: ±2°C temperature corrected
Repeatability: 0.8°C
Response time: 95% of step change in 3 min.
Sample flow: >1 LPM
Temperature
Sensor
-40°C to +70°C ±2°C
Electrical 4/20mA Loop Powered 5-28VDC with HART®
additional TTL level outputs for either HART or Alarm indications
Mechanical 3/4"-16 parallel threads and 1/4" Male NPT threads
All 316 Stainless Steel wetted parts, for fast response time.
Enclosure
Stainless Steel, IP66 & IP68
Dimensions SS enclosure- L: 2.77" (70mm) D: 1.625" (41mm)
Weight Total: 6 oz. (0.17 Kg)
Pressure: 5000 PSIA (345 Bar)
Miscellaneous
Features
NIST traceable calibrations
Units of measure: °C & °F dewpoint, ppmV, ppmW, mB H2O vapor pressure,
grams of H2O / m3and Lbs H2O /106standard cubic feet in Natural Gas
9.2 Model PLMaEx and PLMa-Probe-Ex
Temperature
Range
PLMaEx Analyzer: -20°C to +60°C
Electronics: -40°C to +85°C
Moisture Sensor: -20°C to +60°C
Moisture
Sensor
Range -110°C to +20°C
Accuracy: ±2°C temperature corrected
Repeatability: 0.8°C
Response time: 95% of step change in 3 min.
Sample flow: >1 LPM
Temperature
Sensor
-40°C to +70°C ±2°C
Electrical 4/20mA Loop Powered 5-28VDC with HART®
additional TTL level outputs for either HART or Alarm indications
PLMaEx
3/4" OD tube and 1/4" NPTF Inlet,
1/8" NPTF Outlet
Flow Control Orifice can be placed at Inlet or Outlet;
Built in serviceable/cleanable 100 micron Filter
Pressure: 5000 PSIA (345 Bar)
PLMa-Probe-Ex
1/2"NPT male connection to pipeline valve.
3/8” Swagelok compression seal
Pressure: 1000 PSIA (68 Bar)
Mechanical
All 316 Stainless Steel wetted parts,
Enclosure
Stainless Steel, IP66 & IP68
FM/CSA Explosion Proof Certified Class I, Div I, Groups B, C And D Class II, III, Div 1, Groups E, F And G
ATEX Explosion Proof Certified ATEX 2 GD, Exd I & IIC; IECEx, Exd I & IIC
Dimensions SS enclosure- L: 8.375" (213mm) W: 4.250”" (108mm) H: 2.625”(67mm)
Weight Total: 4 Lbs (1.8 Kg)
Miscellaneous
Features
NIST traceable calibrations
Units of measure: °C & °F dewpoint, ppmV, ppmW, mB H2O vapor pressure,
grams of H2O / m3and Lbs H2O /106standard cubic feet in Natural Gas
13

Appendix A PLMa Installation Drawing
These drawings and any specifications and concepts contained are the property of Phymetrix Inc., are issued
in strict confidence and shall not be used as the basis for the manufacture or sale of apparatus or services, or
reproduced or copied or transmitted in any form or by any means without written permission.
Unless otherwise specified dimensions are in inches .x +/- 0.020" .xx +/-0.010" .xxx +/- 0.005"
Title:
Part Number:
Drawn by: Date: Scale: Page:
Rev:
( )( )
( )
signal and wire colors for molded cable: 1 - brown LOOP + 2 - white Tx out (TTL) 3 - blue LOOP - 4 - black Rx in (TTL) 5 - green/yellow ground to housing, isolated from other 4 pins
Top View
with Molded Cable
Connector Installed
Top View
Molded connector can be installed only in this direction. Screw terminal connectors can be oriented as needed.
PLMa Installation Drawing
0
9/13/10
1:1 1 of 1
BB
+
+ -
-
5 to 28VDC power supply
PLMa pins/sockets
1 3 5
V
sense
V
sense
V
analyzer
V
analyzer
R
sense
R
sense
R
sense
optional shield
brown
blue
green/yellow
PLMa housing could be connected to Earth Ground through pipes
the Voltage across Analyzer (Va), min 5 VDC max 28 VDC.
Power rating of sensing resistor = * R ; Imax = 24mA for a single device
Assuming = 250 Ω Then = 0.024 * 0.024 * 250 = 0.144W
P
r
P
r
I
2
Since the voltage drop across the sense resistor can be 24 mA * 250 Ω =6V then in order to assure that Va is not less than 5V, the
power supply should be no less than 11V. One should also consider the total resistance of the cable when computing the voltage drops for the power supply requirement.
thus should use a minimum 1/4 Watt rated resistor
Limitations:
Measurement Calculations: The PLMa communicates the measured dewpoint to the user by drawing (using) between 4 and 20 mA of power. The user measures this current with a sensing resistor. Typically the sensing resistor Rs is 250 Ω, 200 Ωor 100 Ω. Use a
precision resistor (1% or better) with a power rating of at least 1/4 Watt.
- 4
x 1000 x (H - L)
16
L +PLMa Measured Value =
Where: H = PV output Upper Range as set by HART command #35, read by #15 (factory default +20°C)
L = PV output Lower Range as set by HART command #35, read by #15 (factory default -100°C)
The Measured Value is calculated in the same units as the HART settings for H and L.
If the PLMa housing is not connected to Earth Ground through the pipes then Ground this side of the wire to Earth. Do not ground both sides.
3/4-16 UNF-2A
1.798"
0.390"
1.410"
1.625"
1/4" NPT
0.880"
2.770"
1.898"
O-ring #117 1" OD x 0.103" CS Viton Hard
Connector Phoenix Contact P/N: SACC-DSI-MS-5CON-L180SCO
Mates with all M12 standard connectors
Note: Sample Cell, Manifold or other Mating Surface used with the 3/4"-16 threads must have a sealing surface orthogonal to threads with a minimum of 1" dia. spot-face, free of radial nicks and scratches. Maximum thread countersink diameter of 0.790" to assure proper sealing
1
23
4
5
0.195" dia. cable
Use PTFE tape on NPT threads ONLY.
Hex flats for 1.5" wrench
14

PLMa Installation Drawing
PLMa mounting in Sample Cell
1/4 NPT Run Tee Swagelok SS-400-3-4TFT must be drilled minimum 0.25" deeper with a 7/16" drill
1/4" NPT use Teflon tape
1/4" Swage (2 places)
1/8" NPT (2 places) use Teflon tape
1/4" NPT (2 places) use Teflon tape
The PLMa can be mounted in Swagelok Tees Can use the sample Cell
3/4"-16 parallel threads with O-ring seal
1/4" Female NPT Tee Swagelok SS-4-T other Male/Female combinations can be used
Or
For NPT connection Tighten with 1.5" wrench across flats, 2-3 turns after hand-tight engagement
Hand tighten until metal to metal contact
Welded fittings available optionally
75%
Unless otherwise specified dimensions are in inches .x +/- 0.020" .xx +/-0.010" .xxx +/- 0.005"
Title:
Part Number:
Drawn by: Date: Scale: Page:
Rev:
15