Bulletin P-MS2-M
Series MS2 Magnesense
®
II Differential Pressure Transmitter with Modbus
®
Communication
Specifications - Installation and Operating Instructions
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The Series MS2 Magnesense
Modbus ®
® II Differential Pressure Transmitter with
Communication Protocol combines the proven stable Hall Effect sensing technology of our original MS Series with additional features to reduce installation time and simplify ordering. When using the pluggable integral display, either Metric or English engineering units can be selected by changing the dip switch position. A major benefit of the communications is the transmitters can be daisy-chained together to reduce wiring time and installation cost. The communications allow for the transmitter to integrate seamlessly into the existing building automation control.
Like the original Series MS, the second generation transmitter can display pressure or velocity with the square root extraction internal to the transmitter. Additional parameters have been included to expand the square root capability to include flow measurements.
INSTaLLaTION
Surface Mount:
The transmitter should be mounted on a vertical surface with the connections directed down to prevent moisture from entering either the pressure ports or the electrical cable entry. The diaphragm must be vertical to minimize gravity effects on the diaphragm. Attach the mounting flange to a flat surface using three #8 x 1/2˝ pan head sheet metal screws. Do not over tighten.
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SPeCIfICaTIONS
Service: Air and non-combustible, compatible gases.
Wetted Materials: Consult factory.
accuracy: ±1% FS for 0.25˝ (50 Pa), 0.5˝ (100 Pa), 2˝ (500 Pa), 5˝ (1250 Pa),
10˝ (2 kPa), 15˝ (3 kPa), 25˝ (5 kPa); ±2% FS for 0.1˝ (25 Pa), 1˝ (250 Pa), and all bi-directional ranges.
Stability: ±1% / year FSO.
Temperature Limits: 0 to 150°F (-18 to 66°C).
Pressure Limits: 1 psi max., operation; 10 psi burst.
Power Requirements: 10 to 36 VDC or isolated 21.6 to 33 VAC.
Output Signals: Modbus ® RTU or ASCII 2-wire RS-485 communication protocol.
Response Time: Averaging, adj 0 to 240 s.
Zero & Span adjustments: Digital push buttons.
Current Consumption: 40 mA max.
Display (optional): 5-digit LCD.
electrical Connections: 5-wire terminal block, 18 to 24 AWG.
electrical entry: 1/2˝ NPS thread; Accessory (A-151): Cable gland for 5 to 10 mm diameter cable.
Process Connection: 3/16˝ ID tubing (5 mm ID); Max. OD 9 mm.
enclosure Rating: NEMA 4X (IP66).
Mounting Orientation: Diaphragm in vertical position.
Weight: 8.0 oz (230 g).
agency approvals: CE.
Duct Mount:
The transmitter should be mounted away from fans, corners, heating and cooling coils and other equipment that will affect the measurement of the pressure.
1. To mount the transmitter, drill a 9/16˝ (12.70 mm) diameter hole into the duct.
2. Insert transmitter probe into the duct.
3. Mark location of three mounting holes on duct using mounting flange as template. Drill holes.
4. Attach mounting flange to duct with three #8 x 1/2˝ pan head sheet metal screws. Do not over tighten screws.
DWYeR INSTRUMeNTS, INC.
P.O. BOX 373 • MICHIGaN CITY, INDIaNa 46360, U.S.a.
Modbus ® is a registered trademark of Schneider Automation, Inc.
Phone: 219/879-8000 fax: 219/872-9057 www.dwyer-inst.com
electrical Wiring
NOTICe Wiring should comply with Electrical Characteristics of
Generators and Receivers for Use in Balanced Digital Multipoint
Systems, TIA/EIA-485-A-1998, Telecommunications Industry Association, 1998.
NOTICe Wiring should comply with Modbus ® Communication Protocol
over Serial Line Specification and Implementation Guide V1.02,
Modbus Organization, Inc., 2006
NOTICe Communications wiring must be in a daisy-chain fashion. Star connections are not permitted.
NOTICe Cable shield must be connected to earth ground at one location only.
Figure 1 shows how to connect the MS2 in a network containing a common power supply. Use a cable containing two twisted pairs. One pair is to be used for B(+) and A(-). The other pair is to be used for power and common. This configuration is not suitable for AC supplies. Use a DC supply only. Care should be taken that there are not too many devices powered from the same supply as voltage drops will occur in the wiring. If you have many devices, or have long cable runs, the local supply configuration may be a better choice.
Figure 2 shows how to connect the MS2 in a network containing individual local supplies. Use a cable containing a twisted pair and a single conductor. The pair is to be used for B(+) and A(-). The single conductor is to be used for common. Both
AC and DC supplies are suitable for this configuration.
In either configuration you must use shielded cable. The MS2 has a shield terminal for a convenient location to make connections. It is not electrically connected to the
MS2. Connect the shield to earth ground at one location only to prevent ground loops.
All devices in the network should be daisy chained. Star connections and T connections are not permitted.
The B(+) and A(-) lines must be terminated at both ends with a 120 ohm resistor.
If the MS2 is an end device it has an on-board resistor that may be used. See DIP
SWITCH SETTINGS to enable it.
The network must be biased properly. If needed, there are bias resistors on-board the MS2. No more than two sets of bias resistors should be enabled in the network.
See DIP SWITCH SETTINGS to enable them.
B(+) A(-) PWR COM SHIELD
TO PREVIOUS
DEVICE
B(+)
A(-)
PWR
COM
B(+)
A(-)
COM
COMMON POWER SUPPLY figure 1
B(+) A(-) PWR COM SHIELD
+ figure 2
POWER
SUPPLY
LOCAL POWER SUPPLY
TO NEXT
DEVICE
B(+)
A(-)
PWR
COM
B(+)
A(-)
COM
Dip Switch Configurations
ON
1 2 3 4 5 6 7 8 figure 3
Use the left DIP Switch SW1 to configure the Modbus ® Communication Protocol address of the device. The LCD will show the address when the transmitter is powered on. Valid addresses range from 1 to 247. By default, the device is shipped with the address 127 (as shown in Figure 3). A valid and unused address should be set before connecting to an existing network. However, the address can be changed while the device is operational. If the address is changed, the device will stop responding to the currently configured address immediately. The device waits
15 seconds after the last switch change before applying the new address. The device will not function properly if an invalid address is set. The red LED will periodically blink once indicating an invalid address. The LCD will display “A Err” when the transmitter is powered on if the address is invalid. See Appendix I for setting the Modbus ® Communication Protocol address of the device.
figure 4
Use the right DIP Switch SW2 to configure other hardware and software options.
Table 1: DIP Switch SW2 functions
Switch
1-2 – Display Units
Selection
(See Table 2)
3-4 – Reserved
5 – Full Intelligent Serial
Configuration
6 – B(+) Network Resistor
7 – A(-) Network Resistor
8 – Terminating Resistor
On
Enabled
511Ω Pull-up to 5V
511Ω Pull-down to GND
120Ω between A(-) & B(+)
Off
Disabled
Pull-up not connected
Pull-down not connected
Open
Table 2: Display Units Selection
Switch 1
OFF
ON
OFF
ON
Switch 2
OFF
OFF
ON
ON
Unit
Inches of Water Column (in WC)
Pascal (Pa)
Millimeters of Water Column (mm WC)
Kilo-Pascal (kPa)
NOTICe When using the on-board buttons, there is a 5 second delay from the time the zero or span calibration button is released until the time that the change in calibration takes place. This delay is used to prevent stress related offsets on the lower ranges.
NOTICe The security level that is set in the Programming Menu Section of the manual will determine which calibrations, if any, may be adjusted by the user through the on-board buttons, but the calibration can be changed at any time through the communications.
Zero Calibration
The zero calibration can be set by applying zero pressure to both the pressure ports and pressing the zero button for 3 seconds. If the local LCD is present, the display will read Sero and then sequence back to the home display.
Span Calibration
The span calibration can be adjusted only after setting the zero adjustment. It must be completed within 5 minutes of the last zero calibration. The span calibration button will be ignored until the zero calibration is completed. Apply pressure to the port of the transmitter that is associated with the maximum end of the transmitter range. Press and hold the span button for 3 seconds. If the local LCD is present, the display will read SPAn and then sequence back to the home display. If the span calibration is attempted before adjusting the zero calibration, the FAIL error message will flash on the display.
LCD Display
The Magnesense ® II Differential Pressure Transmitter can be ordered with an optional, integral LCD. If the display is not needed for normal operation, the transmitter can be ordered without the LCD. A Model A-MS2-LCD field upgradeable display is available. It comes with a housing cover with the overlay cut out for the display. The display will plug into the pins as shown in Figure 5.
LCD Pins
DIP Switch
SW1
Display error Messages figure 5 ovEr = The applied pressure is greater than the maximum span value causing an
Over Range Error.
UndEr = The applied pressure is less than the minimum span value causing an
Under Range Error.
FAiL = When the span or zero buttons are pressed, the pressure value is out of the range to allow a correct setting. This may be due to a sensor failure or incorrect pressure being applied.
Err1 = The sensor is damaged.
LCD Pins
DIP Switch
SW2
PROGRaMMING MeNUS
Home Menu
During normal operation, the display will be in the Home Menu and will display the current measured pressure and the engineering units.
Menu access Security
While in the Home Menu, press and hold the Zero and Span buttons simultaneously until SECUr appears on the display in order to access the other programming menus. Upon releasing the buttons, the display will indicate the current security level.
If the current security level is the security level desired (i.e. Security Level 0), press and hold the span button for three seconds to enter the Pressure, Velocity, or Air
Flow Menu.
If the security level is not the desired level, it can be changed temporarily to a lower security level or permanently to a higher level of security by pressing the zero button. A security code will be shown on the display and it can be changed to one of the codes listed in the below table. The span button chooses which digit and the zero button increments the value of that digit. Pressing and holding the span button will store the value.
1
2
3
Security
Level
0
Setting
000
111
222
333
View Menu
Yes
Yes
No
No access edit Menu
Yes
Span
Yes
No
No
No
No
No
No
Zero
Yes
Yes
Yes
No
The level of access to the programming menus and the calibration is limited based on the security level. The above table details the level of access for each security level.
Programming Via Modbus ® Communication Protocol
Supported Modbus ® Communication Protocol Configurations
Modbus ®
Mode
RTU
ASCII
Supported
Baud Rates
9600
19200
38400
57600
76800
115200
Data Size
8
7
Parity
Even
Odd
None 1
None
Even
Odd
None
2
1
Stop Bits
1
2
Intelligent Serial Configuration
Intelligent serial configuration enables the device to determine the baud rate, data size, party, stop bits and even the Modbus ® Communication Protocol mode directly from the serial traffic. This allows the Series MS2 to be quickly and easily deployed after a valid Modbus ® Communication Protocol address is chosen.
To activate intelligent serial configuration, set a valid Modbus ® Communication
Protocol address using the left DIP switch SW1, connect the serial bus and power wires, and then apply power. The device will power up and begin examining the serial bus for communication. The Red LED will repeatedly flash twice, indicating that intelligent serial configuration is in progress.
If the device is setup offline or away from the main network, it is necessary to generate Modbus ® Communication Protocol traffic in order to configure the serial communication. Attempting to read input registers is a good method to generate
Modbus ® Communication Protocol traffic. Note that while serial configuration is in progress, the device may not respond to requests. The device may require multiple read requests to complete the serial configuration process.
The intelligent serial configuration process will complete once a message addressed to the device is received and processed successfully. The serial configuration parameters are then saved to non-volatile storage and loaded by default each time the device starts. If the serial configuration of the bus changes, a power cycle of the device is required to restart the Intelligent Serial Configuration process.
1 The serial configuration, no parity with one stop bit is not officially supported by the Modbus switch 5 on DIP switch SW2 to off. The device will configure itself in Modbus rate will still be determined automatically.
®
® Communication Protocol standard. However, if this configuration is desired, set
RTU Communication Protocol mode with a data size of 8, no parity, and 1 stop bit. The baud
Modbus ® Communication Protocol functions
The device supports the following functions function Name
Read Coils
Read Holding Registers
Read Input Registers
Write Single Coil
Write Single Register
Write Multiple Registers function Code
01
03
04
05
06
16
The String data type is read as a stream of ASCII characters, with the first character sent in the MSB of the first register, and the second character sent in the LSB of the first register and so on. If the string is shorter than the allotted size, the remaining bytes will be zero padded.
Holding Registers
Register
0001
0002-0003
0004-0005
Description
Use default K value. (Default value: 1)
Velocity K value
Area (ft 2 ) Float
Data
Type
Unsigned
16 bit integer
Float
Value
0...1
0...9.999
0.01...999.99
Range
False-True
0...9.999
0.01...999.99
Multi-address
Supported
Yes
Yes
Yes
The holding registers allow configuration of the Velocity K value and Area associated with velocity and flow calculations. By default, both the Velocity K value and Area are set to 1.0. In order to read a correct velocity or flow, these values should be written with appropriate values. The register “Use default K” value indicates to the device if the values in Velocity K value and Area are valid and should be used. Set “Use default K” value to 0 in order to use values written to the
Velocity K value and Area registers.
Coils
The coil registers represent functions of the device. The value returned when reading a coil register indicates the status of the last function execution. If the value is 1, then the last time the function executed was a success. If the value is 0, then the function has either not been executed since power on or failed during the last execution. To execute a function, write 1 to the corresponding register. A response will be returned immediately and the value of the coil will be set to 0. Once the function completes, the value of the coil will be set to 1 if the operation was a success. An application should poll the value of the coil periodically during this time to determine if the function succeeded. If the coil value does not transition to 1 after at most 10 seconds, then the operation failed.
Register
0001
0002
0003
0004
Description
Perform Zero function
Perform Span function
Reset Factory
Defaults
Reset Device
Data
Type
Boolean
Boolean
Boolean
Boolean
Value
0...1
0...1
0...1
0...1
Range
False-True
False-True
False-True
False-True
Multi-address
Supported
No
No
No
No
Coil 1 – Zero function
The zero function will attempt to recalibrate the zero point. This may be needed if the pressure sensor has drifted over time. Note that the zero function will only rezero the sensor if the current pressure is within ±2% of span pressure of the previous zero. If the current pressure is outside the valid band, the zero function will fail and the coil value will remain 0. If the sensor has drifted far enough that the zero function fails, then pressure will have to be applied to bring the current pressure closer to the current zero, and the zero function will have to be executed multiple times until the actual zero is reached.
Coil 2 – Span function
The span function will attempt to recalibrate the maximum positive or negative pressure. Note that accurate span pressure depends on an accurate zero pressure.
The span function will fail if the zero function has not been executed within the last
5 minutes.
Coil 3 – Reset factory Defaults function
The reset factory defaults function resets the zero, span, Velocity K value, Area, and Use Default K Value variables back to their factory default values.
Coil 4 – Reset Device function
The reset device function allows this device to be reset remotely from Modbus ® .
When the reset device function coil is written with a value of 1, the device will immediately respond with success. The reset will take place approximately 5 seconds after the command was received. Writing the value 0 to this coil has no effect.
Multi-address Support
Multi-Address support allows a register to be read or written to using different byte orientations specified by the address range. For example, input register 0003 can also be read at 2003, 4003 and 6003 with different byte orientations as listed in the below table. Registers that do not have multi-address support are only available in
Big-Endian byte orientation (Modbus ® Communication Protocol standard).
Byte Order
Big-Endian
Byte Swap
Word Swap
Little-Endian address Range
1 – 2000
2001 – 4000
4001 – 6000
6001 – 8000 float/32Bit Values
A
B
Register 1
MSB
C
D
B
A
D
C
Register 2
C
D
A
B
LSB
D
C
B
A
A
B
A
B
16Bit Values
Register 1
MSB LSB
B
A
B
A
LeD Status
The device provides three LEDs to indicate status and activity. The LEDs are located to the right of the terminal block and are arranged from left to right as green, yellow, and red. The green LED indicates communication with the pressure sensor.
This LED will flash very quickly most of the time, even without requests from the
Modbus ® interface. The yellow LED indicates Modbus ® communication addressed to this specific device. The frequency and duration of this LED depends on the baud rate and size of request sent. The red LED indicates error states by flashing specific error codes periodically.
1
2
Number of flashes
Solid On (not flashing)
3 error Description
Invalid Factory Configuration
Invalid Modbus ® Communication Protocol Address
Intelligent Serial Configuration in progress, unit may not respond to requests
Communication with pressure sensor failed
MaINTeNaNCe/RePaIR
Upon final installation of the Series MS2 Differential Pressure Transmitter, no routine maintenance is required. The Series MS2 is not field serviceable and it is not possible to repair the unit. Field repair should not be attempted and may void warranty.
WaRRaNTY/ReTURN
Refer to “Terms and Conditions of Sales” in our catalog and on our website. Contact customer service to receive a Return Goods Authorization number before shipping the product back for repair. Be sure to include a brief description of the problem plus any additional application notes.
appendix I: Setting Modbus ®
Switch Position address Value
1
128
ON
1
2
64
2
3
32
4
16
5
8
6
4
7
2
8
1
The address assignment is determined by adding the values for each of the switches that are in the ON position. The transmitter comes from the factory with all of the dip switches, except position 1, in the ON position as shown in Figure 6 below. The address of the transmitter would be 127 as it would be
64+32+16+8+4+2+1=127. Another example would be if the address desired was eight, the only dip switch position in the ON position would be position 5 as shown in Figure 7 below. When power is applied to the transmitter, the LCD (if connected) will display the current address for approximately 10 seconds. If the current address is invalid, the LCD will display “A Err”.
ON
Communication Protocol address of Unit
3 4 5 6 7 8 figure 6: address of Transmitter is 127
1 2 3 4 5 6 7 8 figure 7: address of Transmitter is 8
A
NOTICe Though the minimum possible address would be address 0 when all the dip switch positions were set to OFF, and the maximum possible address would be address 255 when all of the dip switches were set to ON, the transmitter only has valid address from 1 to 247. Any address outside of this range will give an error code.
appendix II: Modbus ® Registers
Register
0001
0002
0003-0004
0005-0006
0007-0008
0009-0010
0011-0012
0013-0014
0015-0016
0017-0018
0019
0020
0021-0022
8001-8006
8007-8012
8013-8018
8019-8024
Description
Pressure in
0.001 inches of water column
Pressure in
Pascal
Pressure in inches of water column
Pressure in
Pascal
Pressure in mm of water column
Pressure in kilopascals
Velocity in feet per minute
Velocity in meters per seconds
Flow in cubic feet per minute
Flow in cubic meters per second
Sensor Type
Data
Type
Signed
16Bit integer
Signed
16Bit integer
Float
Float
Float
Float
Float
Float
Float
Float
Unsigned
16Bit integer
Value Range
Multi-address
Supported
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Pressure
Sensor
Operational
Pressure
Sensor Errors
Modbus ®
Application
Firmware
Version
Sensor
Application
Firmware
Version
Modbus ®
Application
Serial Number
Sensor
Application
Serial Number
Unsigned
16Bit integer
Unsigned
32Bit integer
String
String
String
String
0...3
0...1
0...2
32 -1
0-None,
1-Hall,
2-Piezo,
3-Capcell
Operational-
Nonoperational
0...2
32 -1
Yes
Yes
Yes
No
No
No
No
appendix III: Menu flow Chart
33
W C
WHILE BUTTONS
PRESSED
SECURITY LEVEL
SELECTION
SEC 00
WHEN BUTTONS
RELEASED
SECURITY
TO CHANGE
SECURITY
SS 345
IF SECURITY
0,1,
HOLD 77
SECONDS
FACTORY SETTINGS
RESTORED, THEN
TO
INCREMENT
DIGIT
SELECT
DIGIT
SECURITY LEVEL
00
22
33
000
111
222
333
PRESS ANY
OR
0.0
W
MODE SELECTION
PRESSURE, VELOCITY,
OR FLOW
AA VG
INCREMENT
DIGIT
SELECT
DIGIT
ADJUST PRESSURE
OUTPUT
" "
PoH nn
SPAN
THIS MENU
DIP SWITCH
PoH YY
288 in
INCREMENT
DIGIT
SPAN
SELECT
DIGIT
UNITS SET
WILL
TO " UPDATE
AND
M S
UNITS SELECTED
BY DIP SWITCH
SETTING
SELECTED UNITS
DISPLAYED
Unit
FP
SPAN
ADJUST DISPLAY
K
K
OR
SELECT MAXIMUM
SET PRESSURE OR
VELOCITY oo AdJ
ADJUST VELOCITY
OUTPUT
K uu
K
FP
FPM OR
ON
SPAN
K
M S
TO PoH
MODE
INCREMENT
DIGIT
SELECT
DIGIT
INCREMENT
DIGIT
SELECT
DIGIT
PP
TO "" UPDATE
AND
FROM AVERAGING MENU
SPAN
C M
K
Unit
M H oo AdJ
ARE F
SPAN
SELECT
DIGIT
SQ. METERS BASED
DIP SWITCH SETTING
ARE M
FF
ZERO
PP
M
K
DIP SWITCH SETTING
K
M H
SPAN
ZERO
INCREMENT
DIGIT
SPAN
SELECT
DIGIT
FROM "" UPDATE
AND
UPDATE SECURITY
LEVEL
SEC 00 SEC 11 SEC 22 SEC 33
0.0
W C
©Copyright 2015 Dwyer Instruments, Inc.
Printed in U.S.A. 7/15
DWYeR INSTRUMeNTS, INC.
P.O. BOX 373 • MICHIGaN CITY, INDIaNa 46360, U.S.a.
Phone: 219/879-8000 fax: 219/872-9057
FR# 444021-20 Rev. 3
www.dwyer-inst.com
