Mod-tronic MT300 User manual

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MT300
Three Channel Temperature Monitor
User Manual

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Table of Contents
1 Introduction .......................................................................................................................................... 4
2 Conventions .......................................................................................................................................... 4
3 Installation ............................................................................................................................................ 5
3.1 Mounting................................................................................................................................... 5
3.2 Wiring ........................................................................................................................................ 6
3.2.1 Controller Power......................................................................................................... 7
3.2.2 Inputs .......................................................................................................................... 7
3.2.3 Outputs ....................................................................................................................... 8
3.2.4 Serial Communication................................................................................................. 9
4 Configuration ...................................................................................................................................... 10
4.1 Non-Volatile Configuration Storage ........................................................................................ 10
4.2 Primary Configuration ............................................................................................................. 10
4.2.1 ...................................................................................................................... 12
4.2.2 ...................................................................................................................... 12
4.2.3  ........................................................................................................................ 12
4.2.4 ...................................................................................................................... 12
4.2.5  .......................................................................................................................... 13
4.2.6 ...................................................................................................................... 14
4.2.7  through ................................................................................ 14
4.2.8 ...................................................................................................................... 16
4.2.9  ...................................................................................................................... 17
4.2.10  ...................................................................................................................... 17
4.2.11  ...................................................................................................................... 17
4.2.12  ........................................................................................................................ 18
4.2.13  .......................................................................................................................... 18
4.2.14 ...................................................................................................................... 19
4.2.15 ...................................................................................................................... 20
4.2.16  ........................................................................................................................ 21
4.3 Secondary Configuration......................................................................................................... 21
4.3.1 through  ................................................................................. 21
5 General Usage..................................................................................................................................... 22
5.1 Operation Modes .................................................................................................................... 22

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5.1.1 Monitoring Mode...................................................................................................... 22
5.1.2 Peak Display Mode.................................................................................................... 23
5.1.3 Setup Mode............................................................................................................... 24
5.1.4 Test Mode ................................................................................................................. 24
5.2 Access Restrictions .................................................................................................................. 24
5.3 Special Functions..................................................................................................................... 26
5.3.1 Recovery.................................................................................................................... 26
5.3.2 Error Reporting ......................................................................................................... 26
5.3.3 USB Reset .................................................................................................................. 26
6 MODBUS ............................................................................................................................................. 27
6.1 Holding Registers..................................................................................................................... 27
6.2 Input Registers......................................................................................................................... 31
6.3 Value Format Key .................................................................................................................... 31
7 Specifications ...................................................................................................................................... 40
7.1 Inputs....................................................................................................................................... 40
7.1.1 Power ........................................................................................................................ 40
7.1.2 Sensors ...................................................................................................................... 40
7.2 Outputs.................................................................................................................................... 40
7.2.1 4-20mA loop.............................................................................................................. 40
7.2.2 Relays ........................................................................................................................ 40
7.3 Communication ....................................................................................................................... 41
7.3.1 RS-485 ....................................................................................................................... 41
7.3.2 USB............................................................................................................................ 41
7.4 General .................................................................................................................................... 41
7.4.1 Accuracy.................................................................................................................... 41
7.4.2 Dimensions................................................................................................................ 41
7.4.3 Weight....................................................................................................................... 41
7.4.4 Environmental........................................................................................................... 41
7.4.5 Construction.............................................................................................................. 41
7.4.6 Approvals .................................................................................................................. 41
7.4.7 Factory Defaults ........................................................................................................ 41
8 Glossary............................................................................................................................................... 42
9 Change Log.......................................................................................................................................... 43

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1 Introduction
The MT300 is a universal, three-channel temperature monitor capable of utilizing any combination of the
supported sensor types. Three relay outputs and an internal buzzer are individually configurable to be
tripped by one or more sensor inputs. The included 4-20mA output is fully configurable and may be loop
powered or internally powered. An RS-485 interface and USB port use the MODBUS protocol to configure
the unit as well as read the configuration, sensor values, and peak values. However, all configuration and
available values are accessible via the intuitive front panel interface. Celsius and Fahrenheit scales are
supported.
Separate electrical isolation is provided on the 4-20mA loop, RS-485, and sensor inputs for compatibility
with a wide range of installation environments.
2 Conventions
Several different typestyles are used throughout this manual to make it easier to convey whether the text
refers to a button, indicator, numeric display, output, etc.
In general, if a word or phrase is in all caps (LIKE THIS) it means that it refers to the name of a button or
single LED indicator on the MT300 front panel. Exceptions to this are acronyms such as USB and MODBUS.
If a word or phrase is first letter capitalized (Like This) it means that it refers to the name of a feature, such
as Fan Exerciser, or an input or output, such as Channel 1 or Fan Relay.
If a word or phrase is in an LED display font () it means that it refers to something displayed on
the numeric display.
If a value is preceded by “0x”, that value is in hexadecimal; other numbers should be assumed to be
decimal.
The usage of the words “alarm” and “trip”, in particular, regardless of capitalization, could be confusing.
These two words are industry standard terms for relay outputs on products such as the MT300.
Alarm could refer to the Alarm Relay output, front panel ALARM indicator, or the audible alarm (Buzzer).
However, when referring to the relay output, it is explicitly written as such. When referring to the front
panel indicator, capitalization will be used as previously described to prevent confusion.
Trip can refer to the Trip Relay output, the front panel TRIP indicator, the action of a setpoint being
exceeded, or describing the group of settings that determine a setpoint, and what happens when that
setpoint is exceeded, which is referred to as “trip settings”. Again, the previously described convention
will be used to clarify the intended meaning.
Because of the Reverse Acting Relay feature, specific terms are used to indicate whether a relay’s coil is
actually powered, or if that relay output is in the trip state regardless of the Reverse Acting Relay settings.
If referring to whether a relay’s coil is powered, “energize” will be used. If referring to if a relay output is
in the trip state, “engage” will be used.
If a relay output is engaged, the associated front panel LED will light, however, whether the relay is
energized will depend on the Reverse Acting Relay settings.

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3 Installation
There are no jumpers or user-accessible connections inside the MT300. Instead, it is suggested that the
user determines whether the C or F scale is preferred and set this before further configuration since the
MT300 will not convert existing settings when the scale is changed.
3.1 Mounting
The MT300 should be installed in a rectangular cutout of dimensions 5.6” x 9.0”, or 142mm x
229mm. The dimensions of the MT300 are shown in Figure 1 for reference. It’s easiest to place the
MT300 in the cutout, then mark or directly drill the screw mount holes.
The mounting screws/bolts should be tight enough to compress the foam gasket so as to prevent
debris from entering behind the MT300.
Figure 1

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3.2 Wiring
The rear panel is shown in Figure 2 and provides a visual guide of the terminal block connections.
Each connection is detailed in following sections.
Figure 2

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3.2.1 Controller Power
The MT300 is available in AC and DC models. While the external connections appear
identical, care must be taken to properly connect the appropriate power supply.
The power input for both the AC and DC model is electrically isolated from the rest of the
MT300 circuitry.
3.2.1.1 AC Model
On AC models, the line and neutral must be connected to the L/+ and N/-
terminals, respectively. The remaining connection is earth ground. It is
imperative that the earth ground terminal be properly connected. While the unit
will function without it, failure to do so is a potential shock hazard, may cause
reduced performance, and puts the MT300 at risk for damage due to ESD and
consequently will void the warranty.
3.2.1.2 DC Model
On DC models, the positive and negative must be connected to the L/+ and N/-
terminals, respectively. As with the AC model, the remaining connection is earth
ground, and it is imperative that the earth ground terminal be properly
connected. While the unit will function without it, failure to do so is a potential
shock hazard, may cause reduced performance, and puts the MT300 at risk for
damage due to ESD and consequently will void the warranty.
3.2.2 Inputs
The MT300 can use any combination of supported sensors which are listed in 7.1.2.
The sensor inputs are collectively isolated from the rest of the device, but are not isolated
from each other. Therefore, care must be taken to not create a situation where a voltage
differential can occur between sensors. This is generally an issue only if grounded
thermocouples are used since most RTDs are electrically isolated from the sensor casing.
Each sensor channel has four terminals. Terminals A through C are sensor inputs, and
terminal D is an earth ground connection for sensor lead wire shields. In general, shielded
and twisted pair sensor wires are the best for electrically noisy environments. In addition,
RTDs are generally more immune to noise than thermocouples, and offer better accuracy.
If a shield is provided on a sensor lead, it should be grounded at only one end for best
performance. Which end to ground is usually determined through trial and error since
otherwise it is extremely difficult to determine. Terminal D is provided for this purpose if
the sensor is grounded at the MT300 end.
3.2.2.1 RTDs
Either two-wire or three-wire RTDs may be used. Using three-wire RTDs will allow
the MT300 to automatically compensate for wire resistance as long as all three
wires have the same resistance (i.e. same wire gauge and length).

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When using two-wire RTDs, connect terminals B and C together with a short
jumper, then connect the RTD to terminal A and the junction of B and C. Be aware
that the lead wire resistance on a two wire RTD will be included in the
measurement, and therefore, will be less accurate.
When using three-wire RTDs, the uniquely colored wire is usually the one to
connect to terminal A, and the remaining two similar colored wires should be
connected to terminals B and C. If in doubt, an ohmmeter may be used to
determine which two sensor wires are connected together at the sensor end.
These are the wires that should connect to terminals B and C.
3.2.2.2 Thermocouples
The thermocouple’s positive lead should be connected to terminal A, and the
negative lead should be connected to terminal C. Generally the negative wire on a
thermocouple is red. Terminal B must remain unconnected.
3.2.3 Outputs
3.2.3.1 Relays
Three relay outputs are available: two SPDT relays and one SPST relay. It should
be noted that although the relays have specific names, the function of each relay is
fully programmable with the exception of the Fan relay, which in addition is
permanently linked to the MANUAL FAN button and the Fan Exerciser.
The terminal assignments are indicated on the rear cover of the unit; COM =
Common, NO = Normally Open, and NC = Normally Closed.
3.2.3.2 4 –20mA Loop
A 4 –20 mA output is provided on the MT300. This output will pass a current
between 4 and 20 mA to represent one of the sensor inputs. The output will fall as
low as 3.8mA or as high as 21mA during normal operation in which the loop
output has reached beyond the range defined by the user. The output may also
fall to either 3.5mA or 23mA to indicate a sensor out of range.
The loop may be configured to be external loop-powered or powered by the
MT300.
The loop output is electrically isolated from the rest of the MT300 except when
internal loop power is selected. When internal loop power is selected, it is
electrically connected to the power supply of the MT300, and therefore
electrically connected to the USB port, while other terminals on the MT300 remain
electrically isolated from the loop.

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In environments harboring a high amount of EMI or electrical interference, the 4-
20mA loop cable will need to be wrapped around a ferrite to meet the stated loop
accuracy. This ferrite is generally required only if the 4-20mA loop is used and is in
very close proximity to devices generating a high amount of EMI (such as motors
and radio transmitters). An indication this ferrite is required would be if the 4-
20mA output fluctuates wildly. If the 4-20mA loop output is stable, there is no
need to add anything. Please contact Mod-Tronic if you believe you require this
part and one will be provided free of charge.
For reference, the recommended part is Würth Elektronik 7427153.
3.2.4 Serial Communication
The MT300 includes an RS-485 and USB interface, both of which communicate using the
MODBUS protocol. Either interface may be chosen to communicate with the unit, but both
cannot be used simultaneously. Both interfaces accept the same commands and have
access to the same registers, but USB will typically be used for an easy connection to a
computer, while RS-485 will typically be used when multiple MODBUS devices must be
connected in a network, when other standalone MODBUS devices communicate with the
MT300, or when long bus length is required.
Two LEDs are located near the USB jack; one is labeled COMM and the other is labeled
ERROR. The COMM LED will blink when the selected interface, RS-485 or USB, is sending or
receiving data. This LED will blink when the selected interface receives anything, including
invalid data. The ERROR LED will blink if the MT300 receives a valid MODBUS message with
a function code that isn’t supported by the MT300.
3.2.4.1 RS-485
RS-485 is a differential signaling method that provides high reliability over long
distances and multiple devices on a single network, over a single twisted pair. The
MT300 has two identical sets of terminals for RS-485 connections, each set
containing terminals A, B, and S. Both “A” terminals are electrically identical and
are the non-inverting connections, while both “B” terminals are electrically
identical and are the inverting connections. The “S” terminals are also electrically
identical and are for the cable shield which should be connected in one location
only. A 120Ωtermination resistor will typically be connected across terminals A
and B in each end device in an RS-485 network.
A MODBUS slave ID and baud rate must be selected in the configuration before
the RS-485 interface can be used.
The RS-485 interface is electrically isolated from other MT300 circuitry.
3.2.4.2 USB
The USB interface provides a quick and convenient method of connecting the
MT300 to a computer when an RS-485 interface is not available. The commands
and capability are identical to the RS-485 interface; the USB interface appears as a
COM port to Windows so it may be possible to use some third-party Windows RS-
485 applications with USB.

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In order to use the USB interface, a MODBUS slave ID must be selected and the
baud rate must be set to “”. The Windows application must be set to the COM
port assigned to the USB connection, baud rate set to 19.2K, and no flow control.
The USB interface is not electrically isolated.
The Windows driver is on the included CD under “MCP2200\Driver Installation
Tool”. From there, choose “x86” or “x64” depending on if your Windows
installation is 32 bit or 64 bit, respectively.
4 Configuration
To configure the MT300, Configuration Mode must be entered. To do this, press and hold the
ENTER/MENU button. If no password is set, the Primary Configuration will immediately be presented and
the first menu option, , will be displayed. Otherwise, if at least the Primary Password is set, the
MT300 will ask for the password by displaying . Use the UP and DOWN buttons to change the first
digit to the desired number, and then press ENTER/MENU to accept and move to the next digit. Continue
until all four digits have been set.
If the entered password does not match either the Primary or Secondary Password,  will
momentarily display and will revert back to Monitoring Mode. If the entered password matches the
Primary Password, access to the Primary Configuration will be granted; all configuration settings will be
available. The first menu option, , will be initially displayed. (Note: the front panel TEST button is
protected by the Primary Password)
If the entered password matches the Secondary Password, access to the Secondary Configuration will be
granted; only the trip setpoints will be available. In this case the first menu option of the “setpoint-only
menu”, , will be initially displayed.
Should the user set the Primary Password and the Secondary Password to the same code, the MT300 will
behave as if the Secondary Password is disabled (i.e. set to ).
4.1 Non-Volatile Configuration Storage
All configuration settings are stored to non-volatile memory at the point of exiting Configuration
Mode. When power to the MT300 is lost, or a reset occurs, the configuration is kept intact.
4.2 Primary Configuration
Use the UP and DOWN buttons to cycle through the base menu options, then use the ENTER/MENU
button to select. The specifics of each base menu option are detailed in the following sections. See
Figure 3 for the list and order of the base menu options.
CANCEL may be pressed at any time to back up one menu level at a time. Once a specific setting is
confirmed with the ENTER/MENU button, it is saved and the user may press CANCEL to drop back a
menu level, or pressed repeatedly until the MT300 exits Setup Mode.
If no buttons are pressed while in Setup mode for two minutes, Setup will automatically exit. Any
changes made will be saved. The automatic exit function simulates a press of the CANCEL button.