Michell Instruments Pura User manual

Pura
Online Hygrometer
User Manual
97303 Issue 2
January 2022
PURA

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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.
For Michell Instruments' contact information please go to
www.michell.com
Pura Online Hygrometer
PURA

Pura Online Hygrometer User Manual
iv 97303 Issue 2, January 2022
1 INTRODUCTION ................................................................................................1
1.1 Features ............................................................................................................ 2
2 INSTALLATION ..................................................................................................3
2.1 Unpacking the Instrument ................................................................................... 3
2.1.1 Unpacking Pura Online Hygrometer ................................................................ 3
2.1.2 Unpacking Pura SEN (transmitter, no block version) ......................................... 4
2.1.3 Unpacking Pura OEM-single bag, PRM-double bag versions .............................. 5
2.1.4 Unpacking the Monitor .................................................................................. 5
2.2 Pura Online Components ..................................................................................... 6
2.3 Pura SEN ........................................................................................................... 7
2.4 Pura OEM, PRM .................................................................................................. 7
2.5 Monitor .............................................................................................................. 8
2.5.1 Fault Conditions ............................................................................................ 8
2.5.2 Monitor Controls and Indicators ..................................................................... 9
2.5.3 Electrical Connections .................................................................................. 10
2.5.4 AC Power Supply Input ................................................................................ 12
2.5.5 DC Power Supply Input (Optional) ................................................................ 13
2.5.6 Transmitter Connection ................................................................................ 14
2.5.7 Signal Output Connections ........................................................................... 15
2.5.7.1 Alarm Outputs ..................................................................................... 15
2.5.7.2 Re-transmission Output ........................................................................ 15
2.5.7.3 RS485 Modbus RTU Communications Port ............................................... 15
2.5.8 Mounting the Monitor .................................................................................. 16
2.6 Preparation of the Transmitter Cable .................................................................. 17
2.6.1 Electrical Connections .................................................................................. 17
2.6.2 Sensor Cable Assembly ................................................................................ 18
2.6.3 Cable selection for self-assembled cables ...................................................... 19
2.6.4 Maximum Loop Resistance vs Supply Voltage ................................................ 19
2.6.5 Wiring Connection Between the Transmitter and the Monitor .......................... 20
2.7 Transmitter Mounting ........................................................................................ 21
2.7.1 Sensor Block Connection (Recommended Method) ........................................ 21
2.7.2 Direct Pipeline Connection ........................................................................... 22
2.7.3 Pura OEM & PRM Connection ....................................................................... 23
3 OPERATION ....................................................................................................24
3.1 General Operational Information ....................................................................... 24
3.2 First Time Operation ......................................................................................... 25
3.3 System Alarms ................................................................................................. 26
3.3.1 Reversal of Default Alarm Switching Logic ..................................................... 27
3.3.2 Set-up Alarm Levels .................................................................................... 29
3.3.3 Congure Analog Output Current Loop ......................................................... 30
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

Pura Online Hygrometer User Manual
Michell Instruments v
3.4 Change Dew-Point Temperature Range .............................................................. 31
3.4.1 Span and Unit Settings ............................................................................... 32
3.4.2 Congure Alarm Set-Point Limits .................................................................. 33
3.4.3 Change Scale Units (to ppmV) ...................................................................... 34
4 MEASUREMENT GUIDE ....................................................................................36
4.1 General Operational Guidelines ......................................................................... 36
4.2 Maintenance and Calibration ............................................................................ 38
4.2.1 Clean Monitor ............................................................................................ 38
5 MAINTENANCE ................................................................................................39
5.1 Maintenance and Calibration ............................................................................ 39
5.2 Fault Conditions ............................................................................................... 39
Tables
Table 1 Monitor Front Panel Controls and Indicators ..................................................9
Table 2 Summary of Electrical Connections .............................................................11

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vi 97303 Issue 2, January 2022
Figures
Figure 1 Pura Online Monitor and Transmitter ............................................................1
Figure 2 Unpacking – Monitor and Pura SEN, no block version ....................................3
Figure 3 Unpacking – Monitor and Pura OEM / PRM ...................................................4
Figure 4 Unpacking – Pura OEM & PRM – Single / Double Bag ....................................5
Figure 5 Monitor Unpacking Method ..........................................................................5
Figure 6 Components ...............................................................................................6
Figure 7 Pura SEN ...................................................................................................7
Figure 8 Pura OEM, PRM ..........................................................................................7
Figure 9 Process Indicator panel layout .....................................................................8
Figure 10 Monitor Rear Panel Connections ................................................................11
Figure 11 AC Power Supply Connections ...................................................................12
Figure 12 DC Power Supply Connections ...................................................................13
Figure 13 Transmitter Connections............................................................................14
Figure 14 Digital Communications Port ......................................................................15
Figure 15 Mounting the Monitor ...............................................................................16
Figure 16 Pura Transmitter .......................................................................................18
Figure 17 Pura Transmitter .......................................................................................18
Figure 18 Maximum Load of Pura – Including Cable Resistance ..................................19
Figure 19 Connector Installation ...............................................................................20
Figure 20 Sensor Block Connection ...........................................................................21
Figure 21 Typical display ..........................................................................................25
Figure 22 Change alarm switching logic ....................................................................28
Figure 23 Set-up alarm levels ...................................................................................29
Figure 24 Congure analog output ...........................................................................30
Figure 25 Span and unit settings ..............................................................................32
Figure 26 Set-up alarm set-point limits......................................................................33
Figure 27 Set-up process indicator (to read ppmV ) .....................................................35
Figure 28 Installation Location .................................................................................36
Figure 29 Indication of Dead Space ..........................................................................36
Appendices
Appendix A Technical Specications .............................................................................. 41
Appendix B Quality, Recycling, Compliance & Warranty Information ................................44
Appendix C Return Document & Decontamination Declaration ........................................ 46

Pura Online Hygrometer 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.
Pressure Safety
DO NOT permit pressures greater than the safe working pressure to be applied to the instrument.
The specied safe working pressure is 30 MPa (300 barg/4350 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 Appendix B for details of Michell Instruments’ worldwide oces’ contact information.
Calibration
Periodic re-calibration is recommended in order to maintain the highest quality of measurement in
your application. Michell Instruments recommends that you have your Pura transmitter re-calibrated
annually unless it is used in a mission-critical application or in a contaminated environment, in which
case the calibration interval should be reduced accordingly.
Michell Instruments can oer a variety of re-calibration and exchange transmitter schemes to suit
your specic needs. A local representative will be pleased to provide detailed, custom advice.
Safety Conformity
This product meets the essential protection requirements of the relevant EU & UKCA directives.
Further details of applied standards may be found in the product specication.

Pura Online Hygrometer User Manual
viii 97303 Issue 2, January 2022
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)
ºC degrees Celsius
ºF degrees Fahrenheit
DC direct current
dp dew point
ft foot (feet)
g gram(s)
Hz Hertz
“ inch(es)
lb pound
l/min liters per minute
m meter(s)
mA milliampere
max maximum
min minute(s)
MPa megapascal (Pascals x106)
Nl/min normal liters per minute
Nm Newton meter
ppmV parts per million (by volume)
rh relative humidity
scfh standard cubic feet per hour
V Volts
Ω Ohms
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.

Pura Online Hygrometer User Manual
Michell Instruments 1
INTRODUCTION
1 INTRODUCTION
The Pura Online dew-point hygrometer is an instrument designed for the continuous
online measurement of water dew point in gaseous sample streams, in a diverse range
of applications.
The system comprises a programmable monitor congured to accept a 4...20 mA current
loop signal from the Michell ceramic metal-oxide dew-point transmitter. The span of the
transmitter is set to cover the dew-point range -120 °C...-40 °Cdp (-184 °F...-40 °Fdp)
at operating pressures up to 30 MPa (300 barg/4350 psig).
The monitor also has a re-transmission facility which buers the transmitter output for
onward transmission to other systems. The transmitter input to the monitor is congured
as a 4...20 mA current loop signal and the re-transmitted output can be congured as
either a 4...20 mA or a 0...20 mA current loop signal (ranged as per the input).
Two alarm outputs are provided for connection to external systems. Alarm 1 provides
a set of single pole make contacts and Alarm 2 provides a set of changeover contacts.
Both sets are potential free and Alarm 1 contacts (single pole make) are rated at 250
V, 3 A and the Alarm 2 contacts (changeover) are rated at 250 V, 5 A.
Figure 1 shows the monitor and the transmitter.
PURA
Figure 1 Pura Online Monitor and Transmitter

Pura Online Hygrometer User Manual
297303 Issue 2, January 2022
INTRODUCTION
1.1 Features
The Pura Online Hygrometer is simple to use and install, and can be congured to meet
specic needs.
• ¼” male VCR process connections for PRM and OEM version
½” male VCR process connection for Pura SEN version
• 4...20 mA – sensor signal
• Sensor block compliant with clean room standards
• Measurement range -120 °C...-40 °Cdp (-184 °F...-40 °Fdp)
• Up to ±1 °Cdp accuracy
• Calibration certicate (NPL, NIST)

Pura Online Hygrometer User Manual
Michell Instruments 3
INSTALLATION
2 INSTALLATION
!
It is essential that the connection of electrical and gas supplies
to this instrument be undertaken by competent personnel.
2.1 Unpacking the Instrument
2.1.1 Unpacking Pura Online Hygrometer
The Pura Hygrometer instrument and accessories are packed in a box and the method
of unpacking is shown as follows:
Figure 2 Unpacking – Monitor and Pura SEN, no block version

Pura Online Hygrometer User Manual
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INSTALLATION
Figure 3 Unpacking – Monitor and Pura OEM / PRM
2.1.2 Unpacking Pura SEN (transmitter, no block version)
Unpack the dew-point transmitter from the rectangular cardboard box.
NOTE: The transmitter sensing element is protected while in transit by a red
cover containing a small desiccant capsule. This plastic item is not required
for the operation of the transmitter.
NOTE: Keep the electrical connector in a safe place until the transmitter is
ready for wiring.

Pura Online Hygrometer User Manual
Michell Instruments 5
INSTALLATION
2.1.3 Unpacking Pura OEM-single bag, PRM-double bag versions
Figure 4 Unpacking – Pura OEM & PRM – Single / Double Bag
2.1.4 Unpacking the Monitor
The monitor (2) is packed, together with its xing clamps (1) as shown below.
SMART OUTPUT Module System
Process Indicator
°Cdp
°Fdp
12
Figure 5 Monitor Unpacking Method

Pura Online Hygrometer User Manual
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INSTALLATION
2.2 Pura Online Components
On delivery, please check that all the following standard components are present in the
packing box. Report any shortages immediately.
2
3
1
4
5
7
6
PURA
Figure 6 Components
1. Pura Monitor
2. Clamps
3. Sensor cable assembly
4. Pura Transmitter (SEN) OR
Pura Transmitter (OEM) or (PRM)
Leak test certicate included
5. Screwdriver
6. Power cable
7. Calibration certicate

Pura Online Hygrometer User Manual
Michell Instruments 7
INSTALLATION
2.3 Pura SEN
NOTE: For environmental and operating conditions, refer to Appendix A,
Technical Specications.
Electrical connector
Transmitter cover
Transmitter label
Hexagonal nut
Process connection
Sensing element
Figure 7 Pura SEN
2.4 Pura OEM, PRM
NOTE: For environmental and operating conditions, refer to Appendix A,
Technical Specications.
NOTE: OEM and PRM version transmitters are protected in transit by putting
in a plastic bag lled with nitrogen. Pura OEM transmitter has single bag
protection, Pura PRM transmitter has double bag protection.
Electrical connector
Transmitter cover
Transmitter label
Sensor block
Gas inlet
(see note below) Gas outlet
NOTE: The Pura has a uni-directional connection and must be
connected so the upstream ow is connected to the inlet port
of the Pura block (marked with a silver label).
INLET
Figure 8 Pura OEM, PRM

Pura Online Hygrometer User Manual
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INSTALLATION
2.5 Monitor
The controls and indicators associated with the Pura Online are located on the front
panel of the Process Indicator.
Connections to the Pura Transmitter, the RS485 communications port and the external
power supply are all made to the rear panel of the Process Indicator (refer to Sections
3 and 4).
Figure 9 shows the layout of these controls and Table 1 describes their respective
operational functions.
Pura Online Hygrometer
Figure 9
Process Indicator panel layout
2.5.1 Fault Conditions
Message
Displayed Cause Action
ErrL
Sensor failure
Check power supply to transmitter. Check
transmitter cable for continuity/damage.
Rectify/replace cable
Instrument failure Refer to Michell or local representative for
repair
Sbr Sensor failure or break in
sensor connection
Check transmitter cable for continuity/
damage.
Rectify/replace cable
ErrH
Gas is wetter than -40 °Cdp Check gas source supply
Sensor contaminated Replace/re-calibrate transmitter
outR Input out of range Check gas source supply.
Re-calibrate/replace transmitter
rurC Reverse input connection Swap input connections from the
transmitter to the monitor

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Michell Instruments 9
INSTALLATION
2.5.2 Monitor Controls and Indicators
Item Description
1
°F units indicator
Indicates that the displayed dew-point reading is in degrees Fahrenheit.
2
°C units indicator
Indicates that the displayed dew-point reading is in degrees Celsius.
Note: if neither the °Cdp nor °Fdp LED is lit, ppmVis selected.
3
Main reading display
Displays the value measured by the connected transmitter, or ashes one of the status
conditions shown in Section 2.5.1.
4
AL1
Indicates alarm relay 1 is active, which by default is a LOWLOW alarm.
5
AL2
Indicates alarm relay 2 is active, which by default is a HIGHHIGH alarm.
Section 3.3.2 details the setting up of AL2 trip points.
6
Item Description
6.1 Program Key (P)
6.2 Left arrow (decrement)
6.3 Right arrow (increment)
6.4 Set Key (P)
Table 1 Monitor Front Panel Controls and Indicators

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INSTALLATION
2.5.3 Electrical Connections
Electrical connections to the Pura Online system are as follows:
Required:
• AC power supply, 100 to 240 V AC (-15 %, +10 %), 50/60 Hz, 6 VA. A low
voltage (24 V DC) option is also available.
Optional:
• Transmitter current loop input, 4...20 mA (24 V DC loop power provided
by monitor).
• Alarm 1 (Low), potential free contacts, single pole make. Contacts rated
at 250 V, 3 A.
• Alarm 2 (High), potential free contacts, single pole changeover. Contacts
rated at 250 V, 5 A.
• Re-transmitted input signal from the dew-point transmitter 4...20 mA or
0...20 mA.
• Modbus RTU over RS485 digital communications interface.

Pura Online Hygrometer User Manual
Michell Instruments 11
INSTALLATION
Figure 10 Monitor Rear Panel Connections
Terminal Wire Colour Signal Supply Information
1Blue 0 V (GND) Transmitter Cable Screen
3Green 4...20 mA loop return
4Red Transmitter loop supply
(+ve) +24 V DC w.r.t. terminal 1
7User dened ALR2 (normally closed)
9
7
8
8User dened ALR2 (normally open)
9User dened ALR2 (common)
13 User dened Current loop out (-ve) Default 4...20 mA
14 User dened Current loop out (+ve) Default 4...20 mA
16 User dened ALR1 (common)
16
17
17 User dened ALR1 (normally open)
23 (AC Version) Blue Power in (neutral) 100 – 240 V, 50/60 Hz
24 (AC Version) Brown Power in (live) 100 – 240 V, 50/60 Hz
23 (DC Version) Blue Negative (-) 0 V
24 (DC Version) Brown Positive (+) 24 V
NOTE: There are no terminals in positions
5, 6, 10, 11, 12, 15, 18, 19, 20, 21 and 22
Table 2 Summary of Electrical Connections

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INSTALLATION
2.5.4 AC Power Supply Input
It is essential that the connection of electrical supplies to this
instrument be undertaken by competent personnel.
Connect the AC power supply to the monitor as shown in Figure 11 . Refer also to Table
4 which gives a summary of all the connections to the rear panel of the monitor.
14 15 16 17 18 19 20 21 22 23
2345678910 11
2
1
4
3
Monitor
viewed from underneath
Figure 11 AC Power Supply Connections
1. Ensure that no power is connected to the mains lead.
2. Connect the blue (white – US standard) (neutral) lead (2) to terminal 23
on the rear panel of the monitor.
3. Connect the brown (black – US standard) (live) lead (3) to terminal 24 on
the rear panel of the monitor.
4. Strip back the insulation on the free end of the power cable and wire to
an appropriate power supply plug (brown lead to live supply terminal,
blue lead to neutral supply terminal).
5. Check that the wiring has been completed correctly before connecting to
a mains power supply.