Fox Thermal FT2A User Manual

Fox Thermal

THERMAL MASS FLOW METER

& TEMPERATURE TRANSMITTER

Model FT2A

Modbus & BACnet

Precision Mass Flow Measurement

www.foxthermal.com | 399 Reservation Road Marina, CA. 93933

An ON

CON Brand

105435

Rev. D

Modbus/BACnet

Notice

equipment require repair or adjustment beyond the procedures given herein,

FOX THERMAL

This publication must be read in its entirety before performing any

operation. Failure to understand and follow these instructions could result

in serious personal injury and/or damage to the equipment. Should this

contact the factory at:

FOX THERMAL INSTRUMENTS, INC.

399 RESERVATION ROAD

MARINA, CA 93933

TELEPHONE: 831-384-4300

FAX: 831-337-5787

EMAIL: SERVICE@FOXTHERMAL.COM

Download Technical Data Sheets from our website:

www.foxthermal.com

Fox Thermal believes that the information provided herein is accurate

however be advised that the information contained herein is NOT

a guarantee for satisfactory results. Specically, this information is

neither a warranty nor guarantee, expressed or implied, regarding

performance; merchantability; tness; or any other matter with

respect to the products; nor recommendation for the use of the

product/process information in conict with any patent. Please note

that Fox Thermal reserves the right to change and/or improve the

product design and specication without notice.

Fox FT2A Manuals:

• Model FT2A Instruction Manual

• Fox FT2A View™ Instruction Manual

• Fox FT2A Anybus Manual

Modbus/BACnet

Table Of Contents

1. Modbus Introduction Page 4

2. Modbus Protocol Page 4

3. RS485 Wiring for Modbus Page 5

4. FT2A Commands Supported by Modbus Page 6

5. Modbus Programming Page 12

6. BACnet Introduction Page 17

7. BACnet Protocol Page 16

8. RS485 Wiring for BACnet MS/TP Page 18

9. BACnet Programming Page 19

TABLE OF CONTENTS

10. Glossary of Terms and Abbreviations Page 24

11. Index Page 25

Model FT2A

Modbus/BACnet

Model FT2A

Modbus Introduction

Scope

Thank you for purchasing the model FT2A thermal gas mass ow meter from Fox Thermal. The model FT2A is one of the most technically advanced ow meters in the world. Extensive

engineering effort has been invested to deliver advanced features, accuracy measurement performance and outstanding reliability.

This document describes the Modbus implementation using RS485 serial communication

physical layer for the Fox Thermal FT2A mass ow meter based on the Modicon Modbus

Protocol (PI-MBUS-300 Rev. J).

Modbus Protocol

MODBUS Protocol is an application layer messaging protocol that provides client/sever

communications between devices. MODBUS is a request/reply protocol and offers services specied by function codes.

The size of the MODBUS Protocol Data Unit is limited by the size constraint inherited from the

rst MODBUS implementation on Serial Line network (max. RS485 Application Data Unit = 256

bytes).

MODBUS PROTOCOL

Therefore, MODBUS PDU for serial line communication = 256 – Server address (1 byte) – CRC (2 bytes) = 253 bytes.

RS485 ADU = 253 + Server address (1 byte) + CRC (2 bytes) = 256 bytes.

For more information on MODBUS go to the web site http://www.modbus.org/.

Command Request:

<Meter Address> <Function code> <Register start address high> <Register start address

low> <Register count high> <Register count low> <CRC high> <CRC low>

Command Response:

<Meter Address> <Function code> <Data byte count> <Data register high> <Data

Note: The data in shown in brackets < > represents one byte of data.

Modbus/BACnet

RS485 Wiring: Modbus

RS485 Wiring for Modbus

Wiring connections are made to terminal block TS2 for Modbus communication.

The Tx/Rx+ signal connects to pin 7, Tx/Rx- connects to pin 8 and communication common to pin 9 as shown in Figure 3.1.

Termination Resistor

Connect a termination resistor across the receive/transmit signals of the last device on the Modbus communication line. To connect the 121 ohm termination resistor on the FT2A, set

jumper W1 to the TERM position.

Disconnect the termination resistor on all other external Modbus devices. The termination resistor of the FT2A is disconnected by setting jumper W1 to the NC (Not Connected) position.

Fig. 3.1: Modbus Wiring

MODBUS WIRING

1 2 3

TS7 TS1

Communication Common

TS8

1 2 3

Tx/Rx (+)

Tx/Rx (

TS2

)

Pin 1 of termination resistor header W1

NC (Termination resistor Not Connected)

} }

TERM (Termination resistor installed)

Note: W1 jumper will either be in the NC or TERM position. It should be in the TERM

position on the last meter in the Modbus daisy chain.

Modbus/BACnet

FT2A Commands Supported by Modbus

FT2A Commands Supported

The FT2A supports the following commands:

1) Command 03: Read holding registers

2) Command 04: Read input register.

3) Command 06: Preset single register

Read Holding Registers (command 03)

This command reads the basic variable from the FT2A and has the following format:

Request:

Response:

Example: Request data register at starting address 0x0000 and specifying only 1 register

MODBUS - FT2A COMMANDS

<0x01> <0x03> <0x00> <0x00> <0x00> <0x01> <0x0a> <0x84>

Response:

<0x01> <0x03> <0x02> <xx> <xx> <CRC high> <CRC low>

Where xx xx is the data register value.

Table 4.1: FT2A Modbus Holding Registers

0x00 40001 Flow in Eng units (low) No Mass ow in selected units

0x01 40002 Flow in Eng units (high) No

0x02 40003 Total (low) No Total in selected units

0x03 40004 Total (High) No

0x04 40005 Temperature (low) *10 Temperature in selected units

0x05 40006 Temperature (high) *10

0x06 40007 Elapsed time (low) *10 Elapsed time in hours * 10

0x07 40008 Elapsed time (high) *10

0x08 40009 Velocity (Low) No Velocity in nm/hr

Modbus Address

Data Type Scaling Comment

* 10

FT2A Commands Supported by Modbus

Modbus/BACnet

0x09 40010 Velocity (high) No

0x0A 40011 Flow in Eng units * 10 10 Mass ow in selected units * 10

0x0B 40012 Flow in Eng units *100 100 Mass ow in selected units *

0x0C 40013 Total *100 100 Total in selected units * 100

0x0D 40014 Total2 (low, 2 gas curves only) No Total #2 for 2 gas curves

0x0E 40015 Total2 (high, 2 gas curves only) No Total #2 for 2 gas curves

0x0F 40016 Status No Status

0x10 40017 Spare/ Not used

0x11 40018 Control Register (Write Only) No Control Register

0x12 40019 Spare/ Not used

0x13 40020 Flow in Eng units (oat, upper 16 bits) No Mass ow in selected units

0x14 40021 Flow in Eng units (oat, lower 16 bits) No Mass ow in selected units

0x15 40022 Total in Eng units (oat, upper 16 bits) No Total in selected units

0x16 40023 Total in Eng units (oat, lower 16 bits) No Total in selected units

0x17 40024 Total#2 for 2 gas curve (oat, upper 16 bits) No Total in selected units

0x18 40025 Total#2 for 2 gas curve (oat, lower 16 bits) No Total in selected units

0x19 40026 Temperature in selected units (oat, upper 16 bits) No Temperature in selected units

0x1A 40027 Temperature in selected units (oat, lower 16 bits) No Temperature in selected units

0x1B 40028 Elapsed time in hours (oat, upper 16 bits) No Elapsed time in hours

0x1C 40029 Elapsed time in hours (oat, lower 16 bits) No Elapsed time in hours

0x1D 40030 Velocity in selected units (oat, upper 16 bits) No Velocity in selected units

0x1E 40031 Velocity in selected units (oat, lower 16 bits) No Velocity in selected units

0x1F 40032 Spare/ Not used

0x20 40033 Spare/ Not used

0x21 40034 Spare/ Not used

0x22 40035 Spare/ Not used

0x23 40036 Spare/ Not used

0x24 40037 Total 24 hrs, Last total record, low register No Tot24hrs: Last total record

0x25 40038 Total 24 hrs, Last total record, high register No Tot24hrs: Last total record

0x26 40039 Total 24 hrs, Current Day (0-6) No Tot24hrs: Current Day

0x27 40040 Total 24 hrs, Current Hour (0-23) No Tot24hrs: Current Hour

0x28 40041 Total 24 hrs, Record day 1, low register No Tot24hrs: Record day 1

0x29 40042 Total 24 hrs, Record day 1, high register No Tot24hrs: Record day 1

0x2A 40043 Total 24 hrs, Record day 2, low register No Tot24hrs: Record day 2

0x2B 40044 Total 24 hrs, Record day 2, high register No Tot24hrs: Record day 2

0x2C 40045 Total 24 hrs, Record day 3, low register No Tot24hrs: Record day 3

0x2D 40046 Total 24 hrs, Record day 3, high register No Tot24hrs: Record day 3

0x2E 40047 Total 24 hrs, Record day 4, low register No Tot24hrs: Record day 4

0x2F 40048 Total 24 hrs, Record day 4, high register No Tot24hrs: Record day 4

Modbus Address

Data Type Scaling Comment

100

MODBUS - FT2A COMMANDS

Modbus/BACnet

FT2A Commands Supported by Modbus

0x30 40049 Total 24 hrs, Record day 5, low register No Tot24hrs: Record day 5

0x31 40050 Total 24 hrs, Record day 5, high register No Tot24hrs: Record day 5

0x32 40051 Total 24 hrs, Record day 6, low register No Tot24hrs: Record day 6

0x33 40052 Total 24 hrs, Record day 6, high register No Tot24hrs: Record day 6

0x34 40053 Total 24 hrs, Record day 7, low register No Tot24hrs: Record day 7

0x35 40054 Total 24 hrs, Record day 7, high register No Tot24hrs: Record day 7

0x36 40055 Total 24 hrs, Last Total, low register No Tot24hrs: Last Total

0x37 40056 Total 24 hrs, Last Total, high register No Tot24hrs: Last Total

0x38 40057 Reserved No

0x39 40058 Reserved No

0x3A 40059 Reserved No

0x3B 40060 Reserved No

0x3C 40061 Reserved No

0x3D 40062 Reserved No

0x3E 40063 Reserved No

0x3F 40064 Reserved No

0x40 40065 Reserved No

0x41 40066 Reserved No

MODBUS - FT2A COMMANDS

0x42 40067 Reserved No

0x43 40068 Reserved No

0x44 40069 Reserved No

Modbus Address

Data Type Scaling Comment

* The data in registers with scaling must be multiplied by 10 or 100 as indicated to be scaled properly.

Note: Registers A, B & C are provided to get more resolution for low ow and total. When value exceeds the 16 bit registers, they will be frozen with all 16 bits set. It is also

possible to use the velocity to calculate the ow in engineering units by using the pipe

area and conversion factor for the selected units.

+ 18 hidden pages

Fox Thermal FT2A User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual