PST MICHELL Instruments MDM300 User manual

MDM300
Advanced Dew-Point Hygrometer
User Manual
97122 Issue 16.2
June 2022

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© 2022 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.
MDM300
Advanced Dew-Point Hygrometer
For Michell Instruments' contact information please go to
www.michell.com

MDM300 User Manual
iv 97122 Issue 16.2 June 2022
Contents
Safety ...............................................................................................................................vii
Electrical Safety .........................................................................................................vii
Pressure Safety ...........................................................................................................vii
Toxic Materials ............................................................................................................vii
Repair and Maintenance ..............................................................................................vii
Calibration ..................................................................................................................vii
Safety Conformity .......................................................................................................vii
Abbreviations .................................................................................................................... viii
Warnings .......................................................................................................................... viii
1 INTRODUCTION ................................................................................................1
1.1 Controls and Indicators ....................................................................................... 3
1.2 Function Keys ..................................................................................................... 5
1.2.1 Enter Key ..................................................................................................... 5
1.2.2 Up () and Down () Keys ........................................................................... 5
1.2.3 Right () Key ............................................................................................... 5
1.2.4 Left () / Escape Key .................................................................................... 5
1.3 Instrument Display ............................................................................................. 6
1.3.1 Display Units................................................................................................. 7
1.3.2 Status Display Indications .............................................................................. 8
2 INSTALLATION ..................................................................................................9
2.1 Safety ................................................................................................................ 9
2.2 Unpacking the Instrument ................................................................................... 9
2.3 MDM300 Accessories ........................................................................................ 10
2.4 Operational Requirements ................................................................................. 12
2.4.1 Environmental Requirements – MDM300 Instrument ...................................... 12
2.4.2 Charger Electrical Requirements ................................................................... 12
2.5 Instrument Gas Connections ............................................................................. 12
2.5.1 Gas Inlet /Outlet Fittings ............................................................................. 13
2.6 Connect External Transmitters ........................................................................... 14
2.6.1 Set-Up Pressure Transmitter Parameters ....................................................... 14
2.6.2 Set-Up External Temperature Transmitter Parameters .................................... 15
2.6.3 Set-Up External Dp (Easidew) Transmitter Parameters ................................... 15
2.6.4 Entering User Pressure ................................................................................ 16
2.6.5 Connecting your own Temperature or Pressure Transmitter ............................ 16
2.7 Battery Charging .............................................................................................. 17
3 OPERATION ....................................................................................................19
3.1 Preparation for Operation .................................................................................. 19
3.2 Instrument Start-Up ........................................................................................ 20
3.3 Overall Menu Structure and Operation................................................................ 21
3.3.1 SET-UP Menu .............................................................................................. 21
3.3.2 Chart Page ................................................................................................. 21
3.4 SET-UP Menu Parameters .................................................................................. 23
3.4.1 SETTINGS .................................................................................................. 23
3.4.2 LOGGING ................................................................................................... 24
3.4.3 BLUETOOTH ............................................................................................... 25
3.4.3.1 Bluetooth Pairing Procedure ................................................................... 26
3.4.4 EXTERNAL (Sensor Interface) ..................................................................... 27
3.4.5 CLOCK ....................................................................................................... 28
3.4.6 HMI ........................................................................................................... 29
3.4.7 INFO .......................................................................................................... 30
3.4.8 CHART Page ............................................................................................... 30
3.4.9 LOG FILES Page .......................................................................................... 31

MDM300 User Manual
Michell Instruments v
3.4.10 LOGS Page ................................................................................................. 31
3.4.11 CALIBRATION ............................................................................................. 32
3.5 Default Parameters ........................................................................................... 33
3.6 Guide to Measurement and Sampling ................................................................. 34
3.6.1 Measuring at Atmospheric or System Pressure .............................................. 35
3.6.2 Measurement Guide .................................................................................... 36
3.6.3 Conditional Sensor Purge ............................................................................. 38
3.7 Battery Management ........................................................................................ 38
3.7.1 Battery Troubleshooting ............................................................................... 38
4 GOOD MEASUREMENT PRACTICE .....................................................................39
4.1 Sampling Hints ................................................................................................. 40
5 APPLICATION SOFTWARE ................................................................................43
6 CALIBRATION ..................................................................................................44
6.1 Traceability ...................................................................................................... 44
6.2 Calibration Method ........................................................................................... 45
6.3 Calibration Correction Method ........................................................................... 46
6.3.1 Easidew Oset Adjustment .......................................................................... 47
6.3.2 Easidew One Point Adjustment ..................................................................... 48
7 SHIPPING .......................................................................................................49
Tables
Table 1 Controls and Indicators ................................................................................4
Table 2 Instrument Display Descriptions ...................................................................6
Table 3 Adaptor Fittings .........................................................................................12
Table 4 SETTINGS Parameters ............................................................................... 23
Table 5 LOGGING Parameters ................................................................................24
Table 6 BLUETOOTH Parameters ............................................................................ 25
Table 7 EXTERNAL Sensor Parameters .................................................................... 27
Table 8 CLOCK Parameters ....................................................................................28
Table 9 HMI Parameters ........................................................................................ 29
Table 10 MDM300 Default Parameters ......................................................................33
Table 11 MDM300 Measurement Procedures ............................................................. 36
Table 12 Example Of Calibration Run Readings ..........................................................45
Table 13 Status Register Flags ................................................................................. 55
Appendices
Appendix A Technical Specications .............................................................................. 51
A.1 Dimensions ................................................................................. 52
Appendix B Datalog Status Display ...............................................................................54
Appendix C FCC Declaration .........................................................................................57
Appendix D Quality, Recycling, Compliance & Warranty Information ................................ 59
Appendix E Return Document & Decontamination Declaration ........................................ 61

MDM300 User Manual
vi 97122 Issue 16.2 June 2022
Figures
Figure 1 MDM300 Advanced Dew-Point Hygrometer ...................................................2
Figure 2 User Connections, Controls and Indicators ....................................................3
Figure 3 Instrument Display .....................................................................................6
Figure 4 Packing Method ..........................................................................................9
Figure 5 Gas Port Adaptors ....................................................................................10
Figure 6 Accessories ..............................................................................................11
Figure 7 Bonded Seal Fitting ..................................................................................13
Figure 8 Gas Coupling Examples for Atmospheric Pressure Measurement ...................13
Figure 9 External Transmitter Connection ................................................................14
Figure 10 Typical External Pressure Display ...............................................................14
Figure 11 Typical External Temperature Display .........................................................15
Figure 12 Typical External Dew-Point Display .............................................................15
Figure 13 P/N MDM-27767 .......................................................................................16
Figure 14 Battery Charger Connection ......................................................................17
Figure 15 Start-Up Sequence ...................................................................................20
Figure 16 Menu Structure ........................................................................................22
Figure 17 SETTINGS Page ........................................................................................23
Figure 18 LOGGING Page .........................................................................................24
Figure 19 BLUETOOTH Page ....................................................................................25
Figure 20 Typical Bluetooth Pairing Sequence ............................................................26
Figure 21 EXTERNAL SET-UP Page ............................................................................27
Figure 22 CLOCK Page .............................................................................................28
Figure 23 HMI Page .................................................................................................29
Figure 24 INFO Page ...............................................................................................30
Figure 25 CHART Page .............................................................................................30
Figure 26 LOG FILES Page .......................................................................................31
Figure 27 LOGS Page ...............................................................................................31
Figure 28 CALIBRATION Page ..................................................................................32
Figure 29 Easi-Fit Sample Kit MDM300 Panel-Mount Sampling System .........34
Figure 30 Large and Small Orice Fitting ...................................................................35
Figure 31 Material Permeability Comparison ..............................................................39
Figure 32 Typical Application Software Screen ...........................................................43
Figure 33 Typical 7-point Calibration Certicate .........................................................44
Figure 34 Calibration Page .......................................................................................46
Figure 35 Calibration Menu Page ..............................................................................46
Figure 36 Easidew Oset Adjustment ......................................................................47
Figure 37 Easidew Single Point Adjustment ...............................................................48
Figure 38 Instrument Packing Details ........................................................................49
Figure 39 Dimensions ..............................................................................................52
Figure 40 Current Datalog File Display ......................................................................54
Figure 41 MDM300 Status Register ...........................................................................54
Figure 42 MDM300 Status Register (Hex 28) .............................................................54

MDM300 User Manual
Michell Instruments vii
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
competent personnel using 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 - this battery should never be allowed to fully discharge. The input power
supply voltage limits for the battery charger supplied with the instrument are 90...264 V AC, 50/60
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 specied safe working pressure (SWP), for this instrument is 350 barg (5076 psig).
!
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 oces contact information.
Calibration
The recommended calibration interval for the MDM300 is 12 months. The instrument should be
returned to the manufacturer, Michell Instruments Ltd., or one of their accredited service agents for
re-calibration.
Safety Conformity
This product meets the essential protection requirements of the relevant EU and UK directives.
Further details of applied standards may be found in Appendix D.

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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
bara bar absolute
°C degrees Celsius
°F degrees Fahrenheit
K Kelvin (absolute temperature)
COM common
DC direct current
ft foot (feet)
Hz Hertz
kg kilogram(s)
lb pound
Nl/min liters per minute
m meter(s)
mA milliampere
Mb megabytes
max maximum
min minute(s)
mm millimeter(s)
MPa megapascal
No. number
PIN personal identication number
ppmV parts per million (by volume)
ppmW parts per million (by weight)
psig pounds per square inch
scfh standard cubic feet per hour
SWP safe working pressure
sec second(s)
V volts
Warnings
The following general warning listed below is applicable to this instrument. It is 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.

MDM300 User Manual
Michell Instruments 1
INTRODUCTION
1 INTRODUCTION
The MDM300 Advanced Dew-Point Hygrometer is a portable instrument designed for on-line
measurement of moisture content in non-corrosive gases over an operational range of
-100 to +20 °C (-148...+68 °F).
The instrument is contained within a steel ber-loaded high-impact polyamide 6 case,
sealed to IP66 / NEMA4 standard and is powered by an internally mounted Nickel
Metal Hydride (NiMH) battery, designed to typically provide 48 hours continuous use
between charges. Continuous battery charge status indication is provided. Additional
battery status information is provided by a battery indicator icon, in addition to a warning
beep and Shutdown Mode.
The MDM300 is tted with an internally mounted ceramic sensor, which is enhanced for
a quicker response to dew points as dry as -75 °Cdp (-103 °Fdp).
A 4...20 mA current loop input is provided, which can be programmed to interface with
a number of dierent external transmitter inputs.
• Pressure range 0...350 barg (0...5076 psig)
• Temperature range -100...+100 °C (-148...+212 °F)
• Dew-point (Easidew transmitter) range -100...+20 °C (-148...+68 °F)
A graphical display presents the dew-point data in large format characters and
simultaneously provides a primary display of real time dew-point readings and a
secondary display, in smaller characters, for the external sensor input. If no external
input is programmed, gas temperature (measured by the internal sensor) is displayed
by default.
A fully programmable, real-time, datalogging facility is provided which has an internal
memory capacity of 8Mb, capable of storing up to 10,000 logs per le (typically giving
a maximum of 64 log les).
A Bluetooth, wireless, communication system is provided, giving access to a dedicated,
PC based, MDM300 Software Application Package which provides the facility for handling
the logged data les and uploading and downloading instrument parameters.
A user-friendly operator interface provides easy access to all levels of the instrument’s
functionality.
An easy-to-follow calibration routine is built into the instrument’s software.

MDM300 User Manual
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INTRODUCTION
Two versions of the instrument are available, an MDM300 (standard) version and an
MDM300 (intrinsically safe) version.
This manual covers the MDM300 version only.
For information about the MDM300 I.S. contact your local Michell Instruments’ representative
(contact information at www.michell.com).
Figure 1 MDM300 Advanced Dew-Point Hygrometer

MDM300 User Manual
Michell Instruments 3
INTRODUCTION
1.1 Controls and Indicators
The controls and indicators associated with the MDM300 instrument are located on the
front panel of the instrument.
Connections to the MDM300 dew-point hygrometer, comprising the gas ports, battery
charger input connector and input connector for the external sensor are all made to the top
panel.
Figure 2 shows the layout of these controls and Table 1 describes their respective
operational functions.
Fig 2.1_V6
2
1
3
4
5
6
7
Figure 2 User Connections, Controls and Indicators

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INTRODUCTION
Item Panel Description
1Front Function keys. Refer to Section 1.2 for the details of these
keys.
2Front
Instrument display, partitioned to show 3 main panels:
The primary display shows internal sensor parameters.
The secondary display indicates the external sensor
parameter.
The status display area shows icons representing battery
charge state, initialization in progress, data logging in
progress, keyboard lock status and keyboard beep status.
3Top
Instrument ON/OFF switch.
NOTE: The instrument does not need be switched ON
in order to charge the internal NiMH battery.
4Top Gas Output port. Refer to Section 2.5.
5Top Gas Input port. Refer to Section 2.5.
6Top
Analog input connector for external sensor (pressure,
temperature or dew point).
By default, this signal is displayed in the secondary display
area but may be congured to be displayed as the primary
display.
Spans for each signal input are separately congurable
(refer to Section 2.6).
If no external input is selected, the internal sensor
temperature is shown, on the secondary display, by default
(refer to Section 3.4.6).
7 Top
Socket for connection of battery charger (located behind
cover).
!
ONLY USE THE CHARGER PROVIDED
!
Never allow the battery to fully discharge
Table 1 Controls and Indicators

MDM300 User Manual
Michell Instruments 5
INTRODUCTION
1.2 Function Keys
The function keys, located on the front panel, are used to select operations from the
menus and to select and enter parameter variables within those menu levels.
The function key described is shaded darker and the operation of the keys is as follows:
1.2.1 Enter Key
The Enter key is used within the menus to highlight and select
options and to accept entered values.
Operation of this key from the Main Display causes the Passcode
entry page (for entry to the SET-UP Menu) to be displayed.
1.2.2 Up () and Down () Keys
Within the SET-UP Menu and sub-menus these  and  keys are
used to scroll down and highlight options.
Within sub-menu levels requiring the entry of alpha numeric values,
these keys are used to change the values. Pressing the key once
increases or decreases the selected eld by one step. Pressing and
holding the key will cause the selected eld to be continuously
increased or decreased until the key is released.
1.2.3 Right () Key
Within sub-menu levels requiring the entry of alpha numeric
values, this  key is used to shift the insertion point right in the
le name entry eld.
From the Main Display, pressing this  key moves to the Chart
Page.
From the Chart Page, pressing this  key moves to the Logging
Pages.
1.2.4 Left () / Escape Key
Within sub-menu levels requiring the entry of alpha numeric values,
this  key is used to shift the insertion point left in the le name
entry eld. As the insertion point is shifted to the left, the entry at
the former position is deleted.
Within any menu or sub-menu level, pressing this  key escapes
to the previous menu above the current level.

MDM300 User Manual
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INTRODUCTION
1.3 Instrument Display
The graphics display and the associated function keypad ( Figure 2), form the operator
interface of the equipment. Figure 3 shows all the elements of a typical display page
after the instrument’s initialization period has completed.
Table 2 details the elements of the display:
Dewpoint Internal
°C 12.7
6.9 °C Temp.
Measurement in progress
1234678 5
Figure 3 Instrument Display
Item Description
1
Secondary display
Shows reading from external sensor, if congured; or internal temperature if
external sensor is not congured (refer to Section 3.4.6).
2
Battery charge indicator icon
Flashes when the battery needs charging. A warning beep sounds when the
battery charge level is critical - followed immediately by Shutdown Mode.
NOTE: The icon becomes animated when the charger is connected.
3Keyboard beep indicator
Indicates that the keyboard beep is switched on.
4Keyboard lock indicator
Indicates that the keyboard is locked.
5Datalog status indicator
Indicates that logging is enabled and running.
6
Sensor initializing indicator
Indicates that the initialization process is in progress and that the sensor heating
is on. The presence of this symbol is accompanied by Initializing internal sensor
status message.
7
Primary display
During normal operation, the internal sensor readings are shown in the
primary display. If the external sensor has been congured then this reading
can be shown in this display (refer to Section 3.4.6).
8Status message display area
Displays status and error messages.
Table 2 Instrument Display Descriptions

MDM300 User Manual
Michell Instruments 7
INTRODUCTION
1.3.1 Display Units
The instrument can display the measured reading in the following units:
Absolute Humidity
• g/m3
Moisture Content
• ppmV
• ppmW (AIR, USER, SF6, CO2 or N2)
Dew point
• °C
• °F
• K
Relative Humidity (%)
Mixing Ratio
• g/kg (AIR, USER, SF6, CO2 or N2)
To toggle between displayed units, press either the  or  key.

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INTRODUCTION
1.3.2 Status Display Indications
‘Initializing Internal Sensor’
This is displayed immediately after the instrument has been powered up, and indicates
that the sensor is being heated up to accelerate equilibrium with the moisture in the
sample gas. This has the eect of drying the sensor out, and results in the ‘undershoot’
seen in the rst stage of the measurement process.
‘Measurement in Progress’
This is displayed after the sensor initialization has nished, and indicates that the sensor
is running through the following initial measurement procedure:
1. Undershooting the dew-point
2. Making a rst estimate
3. Running a QRA (Quick Response Algorithm), if necessary
Once the message has disappeared, this indicates that the instrument has nished
its accelerated approach to the actual dew point. Depending on the conditions it may
continue to respond for a number of minutes more, before settling on (or tracking) the
actual measured dew point.
Other Status Display Indications
Internal sensor
error Dew-point reading out of range (> +30 / < -120 °C)
Internal thermistor
error
Sensor internal temperature reading out of range (> +100 /
< -40 °C) or
Thermistor fault
External sensor
error External sensor input out of range (< 4 mA / > 20 mA)
Battery low Battery level low - recharge as soon as possible
Battery low -
recharge now Battery level critical - recharge immediately
Log nished Log le has reached the maximum of 10,000 logs and logging has
been stopped
Internal sensor not
found Could not detect internal sensor on power up
Default CONFIG le
used Cong. le missing, new le created and default settings used

MDM300 User Manual
Michell Instruments 9
INSTALLATION
2 INSTALLATION
2.1 Safety
!It is essential that the installation of the electrical and
gas supplies to this instrument be undertaken by qualied
personnel.
2.2 Unpacking the Instrument
The MDM300 instrument is packed into a standard box and the method of unpacking is
shown below:
12
3
Figure 4 Packing Method
1. Open the box (1) and unpack carefully.
2. Remove the MDM300 (2) and the accessories box (3).
3. Save all the packing materials for the purpose of returning the instrument
for re-calibration or any warranty claims.
4. If the optional carry bag has been ordered it will be located underneath
the foam insert, in a cardboard box.

MDM300 User Manual
10 97122 Issue 16.2 June 2022
INSTALLATION
2.3 MDM300 Accessories
The accessories for the MDM300 are shown in Figure 6 . Items 1...6 are supplied as
standard and item 6 is optional. Please check that all the standard components are
present after unpacking. Report any shortages immediately.
1. Calibration certicate
2. Charger unit
3. Country-specic mains lead
4. Gas Input/Output port adaptors
(three provided - two tted to the instrument - see Figure 5)
5. Quick-start card
6. Carrying case (optional)
Three gas port adaptors are provided, two with a large bore orice and one with a
small bore orice. Depending upon conguration, this permits the instrument to be
run at either system pressure or atmospheric pressure and facilitates the connection of
external ow monitoring and control.
NOTE: On delivery the two large orice adaptors are tted into the instrument’s
gas ports (1 and 2) as shown in Figure 5 . One small orice adaptor is provided
as a loose spare in the accessory pack (see Section 2.5).
Large orice
Gas In Gas Out
Small orice
2 1
Figure 5 Gas Port Adaptors

MDM300 User Manual
Michell Instruments 11
INSTALLATION
1
4
3
6
5
2
Figure 6 Accessories

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12 97122 Issue 16.2 June 2022
INSTALLATION
2.4 Operational Requirements
Operational requirements are as follows:
Sample gas ow rate: 0.2...1.2 Nl/min (0.5...2.5 scfh)
Operating pressure: 0...350 barg (0...5075 psig)
2.4.1 Environmental Requirements – MDM300 Instrument
Operating temperature range: -20...+50 °C (-4...+122 °F)
Humidity: 0...100 % rh (non-condensing)
Altitude: Up to 2000 m (6562 ft)
2.4.2 Charger Electrical Requirements
Charger supply voltage: 90...264 V AC, 50/60 Hz
2.5 Instrument Gas Connections
!
POSSIBLE INJURY! The tubing, valves and other apparatus
attached to this instrument must be adequate for the
maximum pressure which will be applied, otherwise physical
injury to the operator or bystander is possible.
Sample gas connections are made via the Gas In (2) and Gas Out (1) ports located on
the rear of the instrument as shown in Figure 5 .
The MDM300 is supplied with a large bore orice tting installed into the Gas In and Gas
Out ports. These ttings have an 1/8” NPT female thread to allow the user to connect
other components of their choice.
Atmospheric pressure or system pressure dew point can be measured depending on the
conguration of the adaptor ttings as shown in Table 3.
For gas pressures outside the range 2.5...10 barg, the instrument requires external ow
control components, as shown in Figure 8.
Dew point at Gas Inlet port
tting
Gas Outlet port
tting
Sample gas
pressure
Atmospheric Small bore orice Large bore orice 2.5...10 barg
(36...145 psig)
System Large bore orice Small bore orice 2.5...10 barg
(36...145 psig)
Either (using
other ow control
components)
Large bore orice Large bore orice 0...350 barg
(0...5076 psig)
Table 3 Adaptor Fittings