Michell Instruments MDM50 Operating Manual
MDM50
Standard Version
User’s Manual
97475 Issue 1.3
March 2016
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MDM50
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© 2016 Michell Instruments
This document is the property of Michell Instruments Ltd. and may not be copied or
otherwise reproduced, communicated in any way to third parties, nor stored in any Data
Processing System without the express written authorization of Michell Instruments Ltd.
MDM50 LP Version User’s Manual
Contents
Safety ................................................................................................................................ v
Electrical Safety ........................................................................................................... v
Pressure Safety ............................................................................................................ v
Toxic Materials ............................................................................................................. v
Repair and Maintenance ............................................................................................... v
Calibration ................................................................................................................... v
Safety Conformity ........................................................................................................ v
Abbreviations ......................................................................................................................vi
Warnings ............................................................................................................................vi
1 INTRODUCTION ................................................................................................1
2 INSTALLATION ..................................................................................................2
3 OPERATION ......................................................................................................3
3.1 General Operation .............................................................................................. 3
3.2 Atmospheric or Line Pressure Measurements ........................................................ 4
3.3 Measuring Dew Points Below -40°C (-40°F) .......................................................... 5
3.4 User Controls ..................................................................................................... 6
3.5 4-20 mA Output Socket Wiring ............................................................................ 7
4 GOOD MEASUREMENT PRACTICE .......................................................................8
5 MAINTENANCE ................................................................................................12
5.1 Calibration ....................................................................................................... 12
5.2 Transmitter / Battery Replacement ..................................................................... 12
5.3 Filter Cartridge Replacement ............................................................................. 14
5.4 Checking the MDM50 Electronics Calibration ....................................................... 14
5.5 List of Spares ................................................................................................... 14
5.6 Troubleshooting ................................................................................................ 15
Figures
Figure 1 Interchangeable Gas Inlet/Outlet Fittings .....................................................4
Figure 2 User Controls .............................................................................................6
Figure 3 Jack Plug Wiring .........................................................................................7
Figure 4 2-Wire Connection - View Showing Rear of Connector Terminal Block ...........14
Appendices
Appendix A Technical Specifi cations .............................................................................. 17
Appendix B EU Declaration of Conformity......................................................................19
Appendix C Quality, Recycling & Warranty Information ...................................................21
C.1 Pressure Equipment Directive (PED) 97/23/EC ............................... 21
C.2 Recycling Policy ..........................................................................21
C.3 WEEE Compliance ........................................................................ 21
C.4 RoHS2 Compliance ......................................................................22
C.5 Warranty ..................................................................................... 22
C.6 REACH Compliance ...................................................................... 23
C.7 Return Policy ............................................................................... 23
C.8 Calibration Facilities .....................................................................24
C.9 Manufacturing Quality .................................................................. 24
C.10 FCC (EMC Requirements for North America) ..................................24
Appendix D Decontamination Declaration ...................................................................... 26
iv 97475 Issue 1.3, March 2016
MDM50 LP Version User’s Manual
Safety
The manufacturer has designed this equipment to be safe when operated using the procedures
detailed in this manual. The user must not use this equipment for any other purpose than that
stated. Do not apply values greater than the maximum value stated.
This manual contains operating and safety instructions, which must be followed to ensure the safe
operation and to maintain the equipment in a safe condition. The safety instructions are either
warnings or cautions issued to protect the user and the equipment from injury or damage. Use
qualifi ed personnel and good engineering practice for all procedures in this manual.
Electrical Safety
The instrument is designed to be completely safe when used with options and accessories supplied by
the manufacturer for use with the instrument. The instrument is powered by an internally mounted
rechargeable battery. The input power supply voltage limits for the battery charger supplied with the
instrument are 90 to 264 V AC, 47/63 Hz.
NOTE: No other battery charger unit, other than that supplied with the instrument
should be used.
NOTE: Do not allow the battery to fully discharge.
Pressure Safety
DO NOT permit pressures greater than the safe working pressure to be applied to the instrument.
The specifi ed safe working pressure is 20 barg (290 psig). Refer to the Technical Specifi cations in
Appendix A.
Toxic Materials
The use of hazardous materials in the construction of this instrument has been minimized. During
normal operation it is not possible for the user to come into contact with any hazardous substance
which might be employed in the construction of the instrument. Care should, however, be exercised
during maintenance and the disposal of certain parts.
Repair and Maintenance
The instrument must be maintained either by the manufacturer or an accredited service agent. Refer
to www.michell.com for details of Michell Instruments’ worldwide offi ces contact information.
Calibration
The recommended calibration interval for the MDM50 is one year, unless otherwise specifi ed by Michell
Instruments Ltd. The instrument should be returned to the manufacturer, Michell Instruments, or one
of their accredited service agents for re-calibration (go to www.michell.com for contact information).
Safety Conformity
This product meets the essential protection requirements of the relevant EU directives. Further
details of applied standards may be found in the product specifi cation.
Michell Instruments v
Abbreviations
!
The following abbreviations are used in this manual:
AC alternating current
atm pressure unit (atmosphere)
barg pressure unit (=100 kP or 0.987 atm) gauge
°C degrees Celsius
°F degrees Fahrenheit
dp dew point
ft feet
kg kilogram
lb pound
MDM50 LP Version User’s Manual
mA milliampere
m meter
mm millimeter
MPa megapascal
Nl/min normal liters per minute
psig pound(s) per square inch (gauge)
scfh standard cubic feet per hour
μm micrometer
Ω ohm
V Volts
Warnings
The following general warnings listed below are applicable to this instrument. They are
repeated in the text in the appropriate locations.
Where this hazard warning symbol appears in the following
sections, it is used to indicate areas where potentially hazardous
operations need to be carried out.
vi 97475 Issue 1.3, March 2016
MDM50 LP Version User’s Manual
1 INTRODUCTION
The MDM50 comprises a fast responding polymer sensor fi tted into a sample block with
an integrated fi lter cartridge, and Legris push fi ttings or optional Swagelok® tube fi ttings
on the gas inlet and outlet. The measured dew point from the sensor is shown on the
clear red LED display on the front panel of the instrument.
The MDM50 can be supplied with either °C or °F dew-point measurement units.
A 4-20 mA analog output is provided for connection to a chart recorder, data-logger or
computer system, so dew-point trends can be analyzed over time.
The electronics are housed in a rugged Peli case, providing NEMA 6 protection when the
lid is closed. The case is supplied with a lifetime guarantee.
INTRODUCTION
The MDM50 is powered by a rechargeable NiMH battery pack, giving between 12 and
16 hours of measurement time from a full charge. The instrument is delivered complete
with a universal battery charger stored in the lid. It takes 16 hours to fully charge the
battery pack, during which time the instrument can be switched on or off. The charger is
suitable to connect power to the instrument indefi nitely, but it is recommended to allow
the battery pack to go through a full charge-discharge cycle at least once per month. A
battery charge indicator on the instrument front panel warns when the battery is low.
MDM50 polymer moisture sensors are subject to a 9-point calibration, where their
performance is characterized against a fundamental reference hygrometer. This process,
and subsequent quality testing, ensures that all sensors behave optimally before they
are used in the fi eld. Each MDM50 is supplied with a calibration certifi cate traceable to
national standards (NIST) from Michell Instruments' accredited laboratory.
Michell Instruments 1
INSTALLATION
2 INSTALLATION
On delivery, please check that all the following standard components are present in the
packing box:
• MDM50
• 2m of 6mm O/D PTFE tube
• Battery charger
• Mains lead
• 3 pole ¼” jack plug (inside lid) - for analog output connections
• User manual
• Certifi cate of calibration
MDM50 LP Version User’s Manual
Before using the MDM50 for the fi rst time it is recommended that the battery pack is
charged for a minimum of 12 hours.
The case has a pressure relief valve on the exterior below the handle. When closed,
the case is completely sealed. If the instrument is taken through altitude changes, a
pressure differential will occur within the case. If this occurs: Before opening the lid,
open the black pressure relief valve by one turn (anti-clockwise) for a few seconds. This
will equalize the pressures. When the case has been opened, ensure that the pressure
relief valve has been fully closed.
2 97475 Issue 1.3, March 2016
MDM50 LP Version User’s Manual
!
3 OPERATION
Maximum operating pressure is 20 barg (290 psig).
It is important that the gas fi ttings are correctly tightened, and
any tubing is secure in the push fi ttings before use.
Failure to do so will affect the instrument's pressure rating.
3.1 General Operation
To operate the MDM50, follow these instructions:
OPERATION
1. Ensure that all gas fi ttings are fully tightened before use.
2. Gas under test should be restricted to fl ow rates between 1 and 5 Nl/min
(2 and 10.6 scfh) and pressures from atmospheric to 2 MPa (20 barg (290
psig)).
3. Connect the sample gas supply line to the instrument
4. Connect the sample gas vent line to the instrument
5. Switch the instrument on. The display will begin to change as the sensor
responds to the applied dew point.
6. Allow the gas to fl ow until the display shows a stable reading. Typically
this would be around 5 to 15 minutes for spot checks at dew points of
-40°C (-40°F) and above.
7. Switch the unit off and disconnect the sample lines.
NOTE: Filters are essential for potentially dirty/contaminated gases – the
fi tted fi lter should be checked before and after use and replaced regularly - as
required.
Gas In port.
Gas Out port.
Michell Instruments 3
OPERATION
!
MDM50 LP Version User’s Manual
3.2 Atmospheric or Line Pressure Measurements
The MDM50 is supplied with two labelled, interchangeable, gas inlet/outlet fi ttings.
Number Description
1 4mm free fl ow fi tting
2 0.4mm restricted fi tting
Figure 1
§
§
2
Gas Out
LINE PRESSURE
1
Gas Out
ATMOSPHERIC
1
Filter Fitted
2
Filter Fitted
Interchangeable Gas Inlet/Outlet Fittings
§
§
Gas In
Gas In
In order to perform measurements at line pressure, the restricted fi tting should be on
the gas outlet port.
To perform measurements at atmospheric pressure, the restricted fi tting should be on
the gas inlet port.
The Gas In port is ALWAYS on the right hand side.
4 97475 Issue 1.3, March 2016
MDM50 LP Version User’s Manual
3.3 Measuring Dew Points Below -40°C (-40°F)
Due to the signifi cantly lower levels of moisture present at dew points of this level, and
the increased amount of time to dry the system out, the response times of the sensor
will be signifi cantly increased. The table below offers an approximate guide to the
times taken for the instrument to stabilize at a given dew point (from a starting point
of 10°Cdp (50°Fdp) ambient):
OPERATION
Target Dew Point
°C °F
-30 -22 5
-40 -40 15
-50 -58 30
T100 Response Time
(mins)
Michell Instruments 5
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