Emerson MRLDS 450 User manual

MRLDS 450
User Guide
026-1316 Rev 5

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Contents
1 Introduction ......................................................................................................1
1.1 About Manual................................................................................................... 1
1.2 General Safety Requirements............................................................................ 1
1.3 Safe Connection of Electrical Devices ............................................................... 2
2 Product Description ...........................................................................................3
2.1 Intended Uses/Applications .............................................................................. 3
2.2 MRLDS-450...................................................................................................... 3
2.2.1 MRLDS-450 Product Overview ............................................................. 3
2.2.2 MRLDS-450 Design Features ................................................................ 4
2.2.3 MRLDS-450 Component Overview....................................................... 4
3 Installation.........................................................................................................5
3.1 General Information.......................................................................................... 5
3.2 Restrictions...................................................................................................... 5
3.3 Mechanical Installation .................................................................................... 5
3.4 Electrical Installation........................................................................................ 6
3.4.1 Preparations......................................................................................... 6
3.4.2 Power and Signal Wiring....................................................................... 6
3.4.3 Avoiding an Open-Loop Fault Alarm Condition on Power Up................. 7
3.4.3.1 Procedure ............................................................................. 7
3.4.4 Relay Wiring......................................................................................... 7
3.4.5 Modbus RTU RS-485 Interface.............................................................. 8
3.4.6 Conclusion ........................................................................................... 10
4 Operation ..........................................................................................................11
4.1 Overview of Normal Operation......................................................................... 11
4.1.1 Applying Power and the Start-up Sequence.......................................... 11
4.1.2 Verifying Analog Signals....................................................................... 11
4.1.3 Verifying the Modbus Signal................................................................. 12
4.1.4 Status Indication .................................................................................. 12
4.1.5 Switch Functions.................................................................................. 12
4.1.6 Reset System to Factory Default Settings ............................................. 13
4.2 MRLDS-400 Series Application......................................................................... 14
4.2.1 Enable Bluetooth® Connection............................................................ 14
4.2.2 Checking Status ................................................................................... 14
4.2.3 Instrument Conguration.................................................................... 15
4.2.3.1 Change Alias ......................................................................... 15
4.2.3.2 Change Unlock Code ............................................................ 15
4.2.3.3 Change Bluetooth® Passcode............................................... 16
4.2.3.4 Reset to Factory Defaults ...................................................... 16
4.2.3.5 Alarm Conguration ............................................................. 16
4.2.3.6 Modbus Conguration ......................................................... 17
4.2.3.7 Output Conguration ........................................................... 18

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5 Care and Maintenance........................................................................................19
5.1 Maintenance Intervals....................................................................................... 19
5.2 Adjustments ..................................................................................................... 19
5.2.1 Introduction .......................................................................................... 19
5.2.2 General Calibration Procedure .............................................................. 20
5.2.3 Zero Adjustment................................................................................... 21
5.2.4 Span Adjustment ................................................................................... 21
5.2.5 System Bump Test................................................................................. 22
5.3 Troubleshooting ............................................................................................... 22
5.3.1 Hexadecimal Format............................................................................. 22
5.3.2 Fault Codes ........................................................................................... 23
5.4 Sensor Maintenance ......................................................................................... 25
5.4.1 Replacing Sensor Module ...................................................................... 26
5.5 Cleaning the Instrument ................................................................................... 26
6 Additional Information.......................................................................................27
6.1 Sensor Principle ................................................................................................ 27
6.1.1 Electrochemical Sensors ....................................................................... 27
6.1.2 Catalytic Bead Sensors .......................................................................... 27
6.1.3 Semiconductor Sensors ........................................................................ 27
6.1.4 Infrared Sensors .................................................................................... 28
6.2 Disposing of the Instrument ............................................................................. 28
6.2.1 Disposing of the Electrical and Electronic Equipment ............................ 28
6.2.2 Disposing of Sensors ............................................................................. 28
6.3 Technical Specications .................................................................................... 29
6.3.1 General Specications........................................................................... 29
7 Ordering Information.........................................................................................31

1
1 Introduction
1.1 About Manual
Thank you for investing in an MRLDS-450 Gas Detector. To ensure operator safety and the proper use of the
gas detector, please read the contents of this manual for important information about the operation and
maintenance of the instrument.
1.2 General Safety Requirements
NOTICE: Before using this product, carefully read and strictly follow the
instructions in the manual. Ensure that all product documentation is retained and
available to anyone operating the instrument.
DANGER! This instrument is neither certied nor approved for operation in
oxygen-enriched atmospheres. Failure to comply may result in personal injury or
death.
DANGER! This instrument has not been designed to be intrinsically safe for use
in areas classied as being hazardous locations. For your safety, DO NOT use it in
hazardous (classied) locations.
WARNING! Use this product only for the purposes specied in this document and
under the conditions listed.
CAUTION! In the event of an alarm or over-range condition, the sensor must be
re-calibrated to ensure continued accuracy.
CAUTION! This product must be re-calibrated if installed in a non-room condition
environment (For example, temperature or humidity extremes).
CAUTION! The gas diffusion path can become occluded (moisture, dust, debris,
frozen condensation) over time resulting in reduced or complete lack of gas
detection and alarming function. Routine visual inspection of the gas detector
and bump testing are suggested to ensure proper gas detection and alarm
function.
CAUTION! Except for maintenance detailed in this manual, these products
should only be opened and/or serviced by authorized Emerson Technical Support
personnel. Failure to comply may void the warranty.
Safety Icon Explanation
NOTICE: Before installing this product, carefully read and strictly follow the
instructions in the manual.
Table 1.1 - Icons
Imminently hazardous situation which, if not avoided, will result in serious
injury or death.
Potentially hazardous situation which, if not avoided, could result in serious
injury or death.
Potential electrical shock hazard which, if not avoided, could result in
serious injury or death.
Potentially hazardous situation which, if not avoided, could result in physical
injury or damage to the product or environment. It may also be used to alert
against unsafe practices.
Additional information on how to use the product.

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CAUTION! Operator assumes responsibility for complying with all laws, rules and
regulations governing the use of this product.
CAUTION! Use only genuine Emerson parts and accessories. Failure to comply
may impair the operation of the product and/or void the warranty.
CAUTION! Only operate the product within the framework of a risk-based alarm
signaling concepts.
WARNING! The gas diffusion path can become occluded (moisture, dust, debris,
frozen condensation) over time, resulting in reduced or complete lack of gas
detection and alarming function. Routine visual inspection of the gas detector
and bump testing are recommended to ensure proper gas detection and alarm
function. For information on calibrating the sensor, refer to the “Care and
Maintenance” section of this manual.
1.3 Safe Connection of Electrical Devices
WARNING! Before connecting this instrument to electrical devices not mentioned
in this manual, consult the manufacturer or a qualied professional. Failure to
comply may result in personal injury and/or damage to the product.

3
2 Product Description
2.1 Intended Uses/Applications
MRLDS-450 Gas Detection Series instruments continuously monitor ambient air (indoor or outdoor) for the
following gas types:
• Refrigerants
• Oxygen
• Toxic and combustible gases
The MRLDS-450 refrigerant gas detector is designed for use in refrigeration applications and with the
integrated audio-visual alarm indication, can be operated as a stand-alone unit (with additional local alarm
signaling as required), or it may be connected to a facility’s building management system (BMS). It enables
compliance with refrigerant safety codes (ASHRAE 15 and EN378) and alarms to alert personnel in the event
of a refrigerant leak.
DANGER! This instrument is neither certied nor approved for operation in
oxygen-enriched atmospheres. Failure to comply may result in EXPLOSION.
DANGER! This instrument has not been designed to be intrinsically safe for use
in areas classied as being hazardous locations. For your safety, DO NOT use it in
hazardous (classied) locations.
2.2 MRLDS-450
2.2.1 MRLDS-450 Product Overview
The Emerson MRLDS-450 continuously monitors indoor or outdoor ambient air for the following gases:
• Refrigerants
• Oxygen
• Toxic and combustible gases
With the integrated Modbus communication, analog output and relays, the instrument can be operated
as a stand-alone unit or as a third-party device capable of accepting digital and/or analog outputs from the
gas detectors, such as a Building Management System (BMS) or a Supervisory Controller. The instrument is
designed to be installed in non-classied, non-hazardous, permanent locations.
Figure 2.1 - MRLDS-450

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2.2.2 MRLDS-450 Design Features
• Transmitter: IP66 rated ABS enclosure
• Power options:
»24VAC
»19.5 to 28.5VDC
• Diagnostic/Status LED (3 color): Green, Orange, and Red
• Congurable output signal options
» 3× Relays (high alarm/low alarm/fault)
» 1× Analog Output (4 to 20mA, 0 to 5V, 0 to 10V, 1 to 5V, 2 to 10V)
» Digital Output (Modbus RTU signal)
Bluetooth communication allows for full instrument conguration, initiation of calibration, bump test and
functional test mode, and viewing of status information via the corresponding MRLDS-450 iOS/Android app.
Non-intrusive magnetic wand can be used to initiate calibration of the device.
2.2.3 MRLDS-450 Component Overview
# Component Description
1M16 Cable Glands (x6)
2Rubber Gasket
3Internal Alarm Buzzer
4Power Connections (x2)
5Digital Connection (Modbus)
6Analog Connection
7Tactile Switch #1
8Ribbon Cable Connection (To Sensor)
9Tactile Switch #2
10 Relay 3 Connection (FAULT)
11 Relay 2 Connection (HIGH)
12 Relay 1 Connection (LOW)
13 Magnetic (Mag) Switch #1
14 Magnetic (Mag) Switch #2
15 M20 Cable Glands (x2)
Figure 2.2 - MRLDS-450 Component Locations
Table 2.1 - MRLDS-450 Component Descriptions

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3.1 General Information
Every detail of installation site selection is critical to ensure overall system performance and effectiveness.
Strict compliance and considerable thought must be given to every detail of the installation process,
including, but not limited to the following:
• Regulations as well as local, state, and national codes that govern the installation of gas
monitoring equipment.
• Electrical codes that govern the routing and connection of electrical power and signal cables to
gas monitoring equipment.
• The full range of environmental conditions to which the instruments will be exposed.
• The physical characteristics of the gas or vapor to be detected.
• The specics of the application (For example, possible leaks, air movement/draft, etc.)
• The degree of accessibility required for maintenance purposes.
• The types of optional equipment and accessories that will be used with the system.
• Any limiting factors or regulations that would affect system performance or installations.
• Wiring details, including:
»The MRLDS-450 enclosure provides the following cable gland openings:
−2×, M20, supports 10-14mm cable outer diameter
−6×, M16, supports 4-8mm cable outer diameter
»Secondary circuit must be supplied from an isolating source.
»The wiring for the relays must be selected and fused according to the rated voltages,
currents, and environmental conditions.
»If stranded conductions are used, ferrule should be used.
»To comply with RFI immunity regulations, it is necessary to ground the shield of the
communications cable at the PLC, GDA controller, front-end controller or Building
Management System (For example, the chassis, the ground bus-bar, etc.).
3.2 Restrictions
The installation location must have appropriate supply power available for the instrument (For example, 19.5
to 28.5VDC or 24VAC). This ultimately determines the distance the instrument can be mounted from the
controller or power supply.
3.3 Mechanical Installation
3 Installation
CAUTION! The manufacturer of this product requires that a bump test or
calibration be performed following installation to verify instrument functionality.
WARNING! DO NOT allow the lid/sensor to hang from the ribbon cable. Failure to
comply may result in damage to the product.
1. Using the provided hardware, securely mount the MRLDS-450 Gas Detector according to the product
dimensions, maximum wiring lengths and following considerations:
a. Environment: the full range of environmental conditions when selecting a location.
b. Application: the specics of the application (possible leaks, air movement/draft, etc.) when
selecting a location.
c. Accessibility: the degree of accessibility required for maintenance purposes when selecting a
location.
d. Target Gas: the specic gravity of the target gas when selecting the height of the instrument.
2. Using a 5/32” (4mm) hex key/allen wrench (not included) remove the lid and disconnect the
ribbon cable from the base.
3. Set the lid and rubber gasket aside to be reinstalled later.

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3.4 Electrical Installation
3.4.1 Preparations
NOTICE: The MRLDS-450 has a jumper on the analog output. This jumper MUST
be removed to use the analog 4-20mA output signal. If the jumper is removed
AND the 4-20mA output signal is not used, the unit will go into fault.
NOTICE: If analog output is congured for 4 to 20mA output, ensure that the
current loop is connected to a sinking current loop monitor before powering
on the instrument. Otherwise, a fault may be displayed indicating an open loop
condition. If analog output is unused, ensure it is congured as a voltage output
(1-5V) to prevent an open loop fault condition. The analog output is designed as
sourcing.
WARNING! Ensure wiring for relays and connections for sensor(s) are made
before applying power.
CAUTION! This product uses semiconductors which can be damaged by
electrostatic discharge (ESD). When handling the printed circuit boards (PCBs),
observe proper ESD precautions so that the electronics are not damaged.
3.4.2 Power and Signal Wiring
The product comes with cable glands and plugs pre-installed. The power entry cable gland is without a
gland plug. Use the appropriate cable glands to insert and connect the wires for power and signal to the
appropriate terminals as indicated in the gure and wiring table that follow. The PCB terminal blocks are a
pluggable type and may be removed to aid termination.
NOTICE:
• For 24VAC installations sharing a transformer in a daisy-chain conguration,
neutral polarity must be maintained for all instruments.
• 24VAC power polarity must not be reversed.
• For a more robust system, a dedicated transformer for each MRLDS is
recommended to prevent damage caused by wiring errors.
• Fasten terminal screws.
Power Description Label Wiring Termination
Power
24VDC/VAC IN 24V IN: - 24VDC ground/24VAC neutral
24V IN: + 24VDC +/24VAC +
24VDC/VAC OUT
(power daisy chain
terminal)
24V OUT: - 24VDC ground/24VAC neutral
24V OUT: + 24VDC +/24VAC +
Digital Output MODBUS Network
Communications
MODBUS: B RS-485 (-E2E), (+Site Supervisor)
MODBUS: A RS-485 (+E2E), (-Site Supervisor)
MODBUS: GND RS-485 GND
MODBUS: SH RS-485 Shield
Analog
Output
Voltage or Current
Output
ANALOG: - Analog output ground
ANALOG: + Analog output signal (+)
Table 3.1 - Power and Signal Wiring

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The fault can also be cleared by changing the Analog Output to a voltage (0-5V, 1-5V, 0-10V or 2-10V).
3.4.4 Relay Wiring
Relay Function
1Low Alarm
2High Alarm
3Fault Alarm
3.4.3 Avoiding an Open-Loop Fault Alarm Condition on Power Up
To avoid powering up into an Open Loop-Fault. The MRLDS-450 Gas Detector by default has the analog
output congured to 4-20mA. One of the features of the 4-20mA analog output is to alarm the sensor
when an open-loop is detected on the 4-20mA circuit. If the +24VDC power is connected and the circuit is
energized, the MRLDS-450 will detect an open-loop fault and alarm if:
• The 4-20mA circuit is not connected before the sensor is powered, or
• A jumper is not installed and tightened onto the analog output terminal block
3.4.3.1 Procedure
To avoid the open-loop fault on power up, the 4-20mA circuit can be deployed (wiring and congured to BMS
or other) or install a jumper on the analog output terminal block as follows:
Using appropriate cable glands, connect the wires for relay 1, relay 2, and relay 3 to the terminals as indicated
in Table 3-1.
WARNING! Relays are rated for 0 to 30V AC/DC. DO NOT apply main power onto
these relays.
Figure 3.1 - Jumper Installation
Table 3-1 - Relay Wiring Conguration

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When congured according to the factory default settings, the relays are de-energized during normal
operation (not fail-safe). Fail-safe mode can be congured. When congured for Failsafe operation, relays are
energized during normal operation. Failsafe operation ensures reays are triggered in cases of power failure at
the instrument. In Failsafe operation, normally open and normally closed terminals are reversed as indicated
in Table 3-2:
Terminal Normal Operation Failsafe Operation
1Normally Closed Normally Closed
COM Common Common
NO Normally Open Normally Open
The Modbus address, baud rate, stop bit, parity and slave termination is congured through the setup menu.
No jumpers or hardware switch settings are required. Ensure that the communication parameters within the
network, including the BMS, are congured identically.
To ensure optimal performance of the Modbus network ensure the following guidelines are implemented:
• Ensure instruments are congured in a single bus topology, connecting multiple buses in parallel
or branching multiple units from the main bus, may introduce impedance mismatches,
reections and/or signal distortions.
• Avoid long stubs when connecting instruments to the bus, stubs should be less than one
(1) meter in length.
• Ensure A/B signal polarity is maintained throughout RS-485 network.
• Connect cable shield drain to physical earth or ground at the controller only.
• Ensure cable shield integrity is maintained throughout RS-485 network.
For Modbus end-of-line termination, use 150Ω ohm resistor or termination block P/N 537-2711.
Do not use MRLDS 120Ω ohm on-board termination with Site Supervisor or E2.
3.4.5 Modbus RTU RS-485 Interface
For the Modbus RS-485 network use a 16 to 24 AWG (0.5 to 1mm2) 3-core, 2 twisted pair + ground, shielded
cable with 120Ω characteristic impedance.
NOTICE: Recommended: Belden 3105A (or equivalent).
Table 3-2 - Relay Wiring Terminal Conguration

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Site Supervisor Setup - Device and COMM
Figure 3-2 - Site Supervisor Network Setup

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E2 Setup - Device and COMM
3.4.6 Conclusion
After all wiring is completed, power the transmitter and conrm operation, and then prepare to seal the
enclosure.
Align the enclosure gasket (primary transmitter and remote sensor if equipped), replace the lid, and tighten
the six (6) screws. Tightening torque should be limited to tightening by hand, and should be uniform in
pattern.
Figure 3-3 - E2 Network Setup

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4.1.1 Applying Power and the Start-up Sequence
After applying power, the instrument will go through a start-up sequence (initialization, audible/visual test
and self-test sequence). After the start-up sequence completes, the instrument will enter a warm-up period
to allow the sensor element to stabilize before reporting a valid output.
Step Description
1Switch power on.
2
Observe start-up sequence and warm-up phase:
• Green LED will blink at 0.5 Hz for about ve (5) minutes
• Modbus ag for warm-up is set
• Buzzer is off
• Relay state is “no alarm”
• Gas reading invalid
3
Observe normal operation:
• Green LED is steady on
• Modbus ag for warm-up is cleared
• Buzzer is off
• Relay state is “no alarm”
• Gas reading valid
4.1.2 Verifying Analog Signals
The MRLDS-450 gas detector features a single congurable analog output. During normal operation, the
analog output of the instrument is proportional to the detected gas concentration and can be selected from
the following:
• 1 to 5V
• 0 to 5V
• 2 to 10V
• 0 to 10V
• 4 to 20mA (default)
The MRLDS-450 Gas Detector uses different voltage/current values to indicate various modes of operation. In
normal operation the relative gas concentration output is indicated by the analog output level. Output level
is proportional to the gas level as shown in Table 4-2:
Gas Concentration 1-5V 0-5V 2-10V 0-10V 4-20mA
0% 1V 0V 2V 0V 4mA
50% 3V 2.5V 6V 5V 12mA
100% 5V 5V 10V 10V 20mA
4 Operation
4.1 Overview of Normal Operation
CAUTION! Before leaving the instrument for normal operation, check the
conguration for proper settings and check calibration.
Table 4-1 - Instrument Start-up Sequence
Table 4-2 - Gas Concentration Levels

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The instrument may also enter several special states, these are indicated by the specic analog output levels
indicated in Table 4-3
Mode of Operation 1-5V 0-5V 2-10V 0-10V 4-20mA
Instrument Fault ≤ 0.3V N/A ≤ 0.6V N/A ≤ 1.2mA
Offline Mode Maintenance 0.75V N/A 1.5V N/A 3mA
Drift below zero 0.95V N/A 1.9V N/A 3.8mA
Normal operation 1-5V 0-5V 2-10V 0-10V 4-20mA
Measuring range exceeded 5.12V 5.12V 10.25V 10.25V 20.5mA
Fault on analog interface > 5.25V > 5.25V > 10.5V > 10.5V > 21mA
4.1.3 Verifying the Modbus Signal
The MRLDS-450 Gas Detector provides a Modbus RTU digital interface. All status messages and most
parameters that can be accessed and/or congured through the Bluetooth® interface can also be accessed
and/or congured via RS485 for Modbus RTU.
4.1.4 Status Indication
The MRLDS-450 gas detections provide external indication of its current operational state via audible and
visual feedback. Visual indication of the instrument status is provided by a single tri-color LED (Green/
Red/Orange). MRLDS-450 gas detection instruments also provide relays outputs. Instrument states and
corresponding outputs are shown in Table 4-4.
State LED Buzzer Relay 1
(LOW)
Relay 2
(HIGH)
Relay 3
(FAULT)
Warm-up OFF OFF OFF
Normal OFF OFF OFF
Low Alarm ON OFF OFF
High Alarm ON ON OFF
Offline OFF OFF OFF
Fault OFF OFF ON
Negative Gas Fault OFF OFF ON
Zero Cal. Fault OFF OFF OFF
Span Cal. Fault OFF OFF OFF
4.1.5 Switch Functions
User interaction with the MRLDS-450 gas detector is accomplished through the use of two magnetic switches
located on the bottom of each unit. To actuate a magnetic switch, apply the supplied magnetic wand to the
relevant switch location as shown in Figure 4-1.
Table 4-3 - Analog Output Levels
Table 4-4 - Status Indicators

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Switch locations above are referred to in this document as MAG#1 and MAG#2. Depending on the duration
the switch is held, a short “tap” or long “hold” will be detected.
• To carry out a tap function, tap the relevant switch location for one (1) second, until a single “chirp” is
heard and remove the wand to conrm a “tap.”
• To carry out a hold function, do not remove the magnetic wand after the rst “chirp” but continue
to hold for more than ve (5) seconds, until a double “chirp” is heard, and remove wand to conrm a
“hold.” If either switch is held for more than 30 seconds, a stuck switch fault will be indicated.
• To interact with the instrument without use of the magnetic wand, two internal push button tactile
switches may be used. Remove the lid without removing the ribbon cable to access. Internal switches
TACT#1 and TACT#2 mirror the functions of MAG#1 and MAG#2.
The function of each switch depends on the current state of the instrument. Refer to Table 4-1 for switch
functions in each instrument state.
State Switch 1 Tap Switch 1 Hold Switch 2 Tap Switch 2 Hold
Warm-up
Enable
Bluetooth®
Connectivity
Disable
Bluetooth®
Connectivity
Normal Start Zero
Calibration
Start Span
Calibration
Low Alarm Mute Buzzer Ack. Latched Alarm
High Alarm Mute Buzzer Ack. Latched Alarm
Offline
Fault Mute Buzzer Ack. Latched Fault
Negative Gas
Fault Mute Buzzer Start Zero Calibration
Zero Cal. Fault Acknowledge
Fault
Span Cal. Fault Acknowledge Fault
4.1.6 Reset System to Factory Default Settings
To reset system to factory defaults, remove lid and hold TACT#1 and TACT#2 simultaneously for 30 seconds.
Instrument will restart to conrm factory reset. Alternatively, see Section 4.2.3.4., Reset to Factory Defaults,
for instructions on resetting instrument conguration via the MRLDS-400 Series App.
Figure 4-1 - Magnetic Switches
Table 4-1 - Switch Functions

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4.2. MRLDS-400 Series Application
Download the MRLDS-400 Series App.
The companion smartphone application allows users to perform a variety of functions to congure and
interact with the MRLDS-450 gas detector, including:
• View real-time measurements
• Congure instrument
• Test outputs
• Calibrate/Bump test instrument
• Generate customizable calibration certicates
4.2.1. Enable Bluetooth® Connection
1. Enable Bluetooth® discovery by tapping MAG#1 for 1-second. (After 10 seconds, the device will
indicate that it is discoverable with audible heartbeat until it has been paired, discovery has
timed-out, or has been canceled.)
2. Launch the MRLDS-400 Series App and select the Bluetooth® icon at the bottom of the screen to
initiate a scan.
3. Select MRLDS-450 default alias is “18TMAE” from the list of available gas detectors.
4. When prompted, enter the passkey (default is “123456”).
4.2.2. Checking Status
No. Description
1Alias, user-congured instrument name.
2Serial, instrument 8-digit serial number.
3Gas, gas type currently detected by instrument.
4Status ring, provides visual indication of various instrument states (expanded on Table 4-2)
5Live measurement, current measurement in given measurement units. Measurement unit,
displayed measurement unit (PPM/PPB/%LEL/%VOL)
6Measurement unit, displayed measurement unit (PPM/PPB/%LEL/%VOL)
NOTICE: Default alias, passkey, and unlock code can be changed via the
MRLDS-400 Series App’s conguration menu. Default values should be changed
after instrument installation for security purposes.
Current Instrument status can be viewed from the Home tab. The Home tab displays the following status
information:
Figure 4-2 - MRLDS-400 Series App Home Tab
Table 4-1 - MRLDS-400 Series App Home Tab Features

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State Status Ring Description
Warm-up Green Gas detector stabilizing after power on or restart.
Normal Green Normal Operation.
Low Alarm Yellow Gas measurement has exceeded low alarm setpoint.
High Alarm Red Gas measurement has exceeded high alarm setpoint.
Offline Orange Gas Detector in maintenance mode and is not actively
monitoring gas.
Fault Orange A fault has been detected.
Negative Gas Fault Orange Gas Detector calibration has drifted below zero, requires
zero calibration.
Zero Cal. Fault Orange Error occurred during zero calibration. Zero calibration has
not be updated. Zero calibration required.
Span Cal. Fault Orange Error occurred during span calibration. Span calibration has
not be updated. Span calibration required.
4.2.3. Instrument Configuration
For security, access to conguration and calibration options are restricted to authorized users only. Access to
these functions require use of an unlock code.
To unlock instrument conguration, go to the Configure tab to set up the device. When prompted, enter
unlock code to access device conguration. (The instrument’s default code is “1234”). Instrument will
remain unlocked until Bluetooth® connection has ended.
NOTICE: Default alias, passkey, and unlock code can be changed via the
MRLDS-400 Series App’s conguration menu. Default values should be changed
after instrument installation for security purposes.
4.2.3.1. Change Alias
To allow easy identication of a given instrument, an alias can be assigned to each instrument. This alias is
displayed when searching for an instrument via Bluetooth®, on Calibration Cert and in the Home tab. To set
the alias:
• On the Configure tab select Alias. Enter the required alias for instrument and select OK.
• The instrument must be restarted for change to take effect. Selecting the Home tab then Restart will
reboot device.
• Reconnect to instrument to conrm the alias has been updated.
4.2.3.2. Change Unlock Code
To prevent unauthorized access to instrument conguration and calibration, the default instrument unlock
code should be changed during commissioning. To change unlock code:
• On the Configure tab select Modbus Unlock Code. Enter the new 4-digit unlock code for instrument
and select OK.
• The instrument must be restarted for changes to take effect. Selecting the Home tab, then Restart will
reboot the device.
• Reconnect to instrument to conrm the unlock code has been updated.
NOTICE: If the custom unlock code is forgotten, the unlock code may be reset
to default value (1234) by resetting system to factory defaults. Refer to Section
4.1.6., Reset System to Factory Default Settings for the system reset procedure.
Note that a system reset will return all custom system congurations to defaults.
Table 4-2 - Status Ring of Various Instrument States

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4.2.3.3. Change Bluetooth® Passcode
To prevent unauthorized access to instrument status, the default instrument Bluetooth® passcode code
should be changed during commissioning. To change Bluetooth® passcode:
• On the Configure tab select Bluetooth Passcode. Enter new 6-digit passcode for the instrument and
select OK.
• The instrument must be restarted for changes to take effect. Selecting the Home tab, then Restart will
reboot the device.
• Reconnect to instrument to conrm the Bluetooth® Passcode has been updated.
NOTICE: If the custom passcode is forgotten, the unlock code may be reset to
default value (123456) by resetting system to factory defaults. Refer to Section
4.1.6., Reset System to Factory Default Settings for system reset procedure. Note
that a system reset will return all custom system congurations to defaults.
4.2.3.4. Reset to Factory Defaults
Instrument conguration may be reset to factory defaults via the smartphone application:
• On the Configure tab select Reset to Factory Default and select OK to conrm.
• The instrument will automatically restart and disconnect from the smartphone application.
WARNING! Resetting system to factory defaults will remove all custom system
conguration including unlock code and Bluetooth passcode. After system
reset custom unlock and Bluetooth passcodes should be congured to prevent
unauthorized access and reconguration of instrument.
4.2.3.5. Alarm Configuration
Low Alarm Setpoint
The value above which a low alarm condition occurs. The low alarm setpoint must be less than the high alarm
setpoint and greater than the low alarm limit. The low alarm limit is the xed minimum limit that is sensor–
specic and not editable.
Range of acceptable setpoints is displayed when updating the parameter. To update the setpoint:
• On the Configure tab select Alarm then Low Alarm Setpoint. Enter the new setpoint and select
OK to conrm.
NOTICE: In instruments with an oxygen sensor installed, low alarm behavior
operates in a depletion mode where gas measurements BELOW the low alarm
setpoint initiate a low alarm. This allows monitoring of oxygen displacement and
enrichment scenarios.
NOTICE: To prevent intermittent alarm operation at the setpoint due to
measurement noise this instrument implements hysteresis at the setpoint. Once
the alarm level is exceeded, the gas measurement must return a xed percentage
below the alarm threshold before the alarm is disabled. Typical hysteresis value is
set at 5% of full scale; however, this is sensor-specic and non-editable.
High Alarm Setpoint
The value above which a high alarm condition occurs. The high alarm setpoint must be less than the sensor
full scale range and greater than the low alarm setpoint.
Range of acceptable setpoints is displayed when updating the parameter. To update setpoint:
• On the Configure tab select Alarm then High Alarm Setpoint. Enter the new setpoint and
select OK to conrm.
NOTICE: To prevent intermittent alarm operation at the setpoint due to
measurement noise, this instrument implements hysteresis at the setpoint. Once
the alarm level is exceeded, the gas measurement must return a xed percentage
below the alarm threshold before the alarm is disabled. Typical hysteresis value is
set at 5% of full scale; however, this is sensor-specic and non-editable.

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Alarm Latching
Enabling alarm latching will maintain alarm or fault condition even after the alarm or fault condition is
no longer active. When latched, the alarm or fault condition must be manually acknowledged before the
condition will be cleared. This allows transient alarm or fault conditions to be identied.
If an alarm is latched, for example, the condition has occurred but is no longer active, an acknowledgment
button will appear on the Home screen. Select this button to acknowledge the latched condition and clear
the alarm or fault.
When disabled, the alarm or fault status clears automatically as soon as the condition is no longer active. To
congure:
• On the Configure tab select Alarm then Alarm Latching. Select Enable/Disable and OK to conrm.
4.2.3.6. Modbus Configuration
Address
Sets instrument address for connection to RS-485 Modbus interface. (Default: 1). To set address:
• On the Configure tab select Modus, then Address. Select 1-247 and OK to conrm.
NOTICE: Ensure all instruments on RS-485 bus have been congured with unique
node addresses. If two instruments have been congured with same address, bus
contention will occur preventing communications with these instruments via the
RS-485 interface.
Baud Rate
Sets instrument baud rate for connection to RS-485 Modbus interface baud). To set baud rate:
• On the Configure tab select Modus then Baud Rate. Select 9600/19200 (default) and OK to conrm.
Stop Bits
Sets instrument stop bits for connection to RS-485 Modbus interface (Default: 1 stop bits). To set number of
stop bits:
• On the Configure tab select Modus then select Stop Bits. Select 1 or 2 and OK to conrm.
Parity
Sets instrument parity for connection to RS-485 Modbus interface (None, Odd, or Even (default). To set
parity:
• On the Configure tab select Modus then select Parity. Select None/Odd/Even and OK to conrm.
NOTICE: Stop bits must be set to 1 where parity is Odd or Even.
Enable 120Ω Termination
For optimal communication reliability, in RS-485 Modbus networks the last instrument physically connected
to the RS-485 bus must include a 120Ω termination resistor. This is to reduce the potential for electrical
signal reection on long buses due to impedance mismatches. Typically, this requires a physical resistor with
the same characteristic impedance of the bus cable to be installed on the bus.
MRLDS-450 instruments include this termination resistor on all instruments and allow this termination to
be enabled via this conguration setting without the need for an external physical resistor. To enable this
termination resistor:
• On the Configure tab select Modbus then select Enable 120Ω Termination. Select
Enable/Disable and select OK to conrm.
NOTICE: Termination resistor should only be enabled on last instrument physically
connected to RS-485 bus. An external resistor should not be connected where
this is enabled on the instrument.