Omega CN8260, CN8240 User Manual

CN8240 & CN8260 Series Communications & Options

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CN8240 &

CN8260

SERIES

Communications &

Options Guide

User’s Guide

CN8240 & CN8260 Series Communications & Options

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The information contained in this document is believed to be correct, but OMEGA Engineering, Inc. accepts no liability for any errors it contains,
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WARNING: These products are not designed for use in, and should not be used for, patient-connected applications.

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CN8240 & CN8260 Series Communications & Options

Table of Contents

For information and instructions related to basic operations, refer to the CN8240/CN8260
operator’s manual supplied with your controller.

Option Wiring Diagrams

Alarm Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

24 Volt DC Alarm Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Relay, N.O. Alarm Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

RS-232 Communications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

RS-485 Communications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Transducer Excitation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Auxiliary Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Remote Analog Setpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Guide to Digital Communications

Remote Communications Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Omega+ Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

• Message Formats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

• Sample Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10

• Request Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-13

• Response Messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15

• Communications Parameter List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-21

• Auxiliary Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 23

• Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-26

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1

2

3

1
1

12

13

23

24

RCV

B(-)

XMT

A(+)

SIG GND
SIG GND

RS 232
RS 485

Relay, N.O.

OUTPUT 2

N.O.

C

N.O.

2

3

12

13

14

15

16

17

18

23

24

8

9

1
0

19

2
0

21 22

4

5

6

7

N.O.

C

N.O.

C

ALARM 1

L1

L2

ALARM 2

120-250 V

50-60 Hz

+

–

+

Alarm Output

Option -AL1, -AL2: Relay, N.O. Alarm Output

CN8240 & CN8260 Series Communications & Options

Supply voltage*

Supply voltage*

Load 5 amp fuse

Load 5 amp fuse

Option Description: NO (Normally open) relay contact is closed when either alarm is active. The relay life is greater
than 100,000 operations at 5 operations per second switching full load.

*Connect load and supply voltage per the following table:

Load Type 5 A Voltage Limit

Resistive dc 30 Vdc

Inductive ac (L/R = 7 ms) 20 Vdc

Resistive ac 250 Vac

Inductive ac (pF = 0.4) 150 Vac

Motor, ac, 1/6 hp 250 Vac

Tungsten Lamp, 360 W 120 Vac

RS-232
Communications

Option -C2: RS-232 (one-to-one) Communications

RCV XMT SIG GND

Option Description: Provides a one-to-one connection between the controller and an RS-232 port. Computers,

PLCs, or dumb terminals may be used to set and access controller data.

1

CN8240 & CN8260 Series Communications & Options

1

2

3

1
1

12

13

23

24

RCV

B(-)

XMT
A(+)

SIG GND
SIG GND

RS 232
RS 485

+

–

NOTE: FOR 2 WIRE RTD

JUMPER 18 & 20

3

12

13

14

15

16

17

18

8

9

1
0

19

2
0

21 22

4

5

6

7

T/C

+

–

RTD

MA
MV

V

SENSOR

INPUT

RS-485
Communications

Option -C4: RS-485 (one-to-many) Communications

B(-) A(+) SIG GND

JMP 1

Option Description: Provides one-to-many communications.

Terminate the controller furthest from the computer by either connecting a 120-ohm, 1/4-watt resistor between ter­minals 23 and 24 or using jumper 1 located on the underside of the communications board as shown above.

Transducer
Power Supply

Options -XP1, -XP2, -XP3, -XP4: Transducer Power Supply

0 to1 volt out = 0 to100% RH

(6 to 30 Vdc input)

Option Description: The transducer power supply option provides power to remote transducers. The transducer
outputs, in turn, provide a signal to the controller input which can be scaled in the appropriate engineering units.

Option -XP1: 15 Vdc
Option -XP2: 12 Vdc
Option -XP3: 10 Vdc
Option -XP4: 5 Vdc

All options will provide at least 20 mA. The transducer circuitry is thermally protected from short circuits.

2

CN8240 & CN8260 Series Communications & Options

+

–

NOTE: FOR 2 WIRE RTD

JUMPER 18 & 20

2

3

12

13

14

15

16

17

18

23

24

8

9

1
0

19

2
0

21 22

4

5

6

7

T/C

+

–

RTD

MA
MV

V

SENSOR

INPUT

–

14

15

16

17

18

8

9

19

21 22

4

5

6

7

T/C–RTD

MA
MV

SENSOR

INPUT

1

12

13

14

15

16

17

24

1

12

13

14

15

16

17

24

Process Output

Options -PVSV1, -PVSV2: Process Output

Connect jumper between pins 16 and
17 for option -PVSV2

Option PVSV2
(0-5 V)

Option -PVSV1
(4-20 mA)

Option Description: The Setpoint Variable or Process Variable is transmitted to a remote device (chart recorders,
indicators, data recorders, computers, process controllers, etc.) with 1 of 2 different interfaces:

Option -PVSV1: 4-20 mA

Option -PVSV2: 0-5 V
The output signal is scalable in the Auxiliary Output Menu. Multiple remote indicators may be driven by the controller.
For current (mA) options, the remote indicators are connected in series. The sum of the input resistance for all

remote indicators must be less than 400 ohms. For voltage options, the remote indicators are connected in parallel.
The sum of the currents for all remote indicators must be less than 10 mA.

Remote
Setpoint Options

Options -DIC, -RSP4, -RSP5, -RSP6, -RSP7: Remote Setpoint

Options -RSP4, -RSP5, -RSP6, -RSP7

0-5 V/1-5 V/0-10 V
0-20 mA/4-20 mA

}

Enable
Switch

→

10K

CW

Remote analog setpoint

(voltage/current input)

(potentiometer with
enable switch)

Option Description: Remote setpoints use either voltage or current inputs, depending on the specified option:

Option -DIC: Switch Input Closed
Option -RSP4: 0-5 Vdc
Option -RSP5: 1-5 Vdc
Option -RSP6: 0-20 mA

Option -RSP7: 4-20 mA
The input signal is scalable in the Remote Analog Setpoint Menu. Activation of the analog setpoint causes the F1
indicator to illuminate. For current (mA) options, the input resistance is 255 ohms. For voltage input options, the
input resistance is greater than 10K ohms.

input option menu controls the programming of this switch.

*Ground shield at one end, taking care not to run wires next to power circuitry. Maximum length will be determined

by noise performance.

Note: Switch input option -DIC is active when switch is closed. The digital

3

Option -DIC

Switch input onlyRemote analog setpoint

Enable
Switch

CN8240 & CN8260 Series Communications & Options

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CN8240/CN8260 Series

Controllers

with

Digital

Communications

Option

4

CN8240 & CN8260 Series Communications & Options

1

2

3

1
1

12

13

14

15

16

23

24

4

5

6

RCV

B(-)

XMT
A(+)

SIG GND
SIG GND

RS 232
RS 485

DIGITAL COMMUNICATIONS

Digital
Communications Option

Remote Communications Options

RS-232

This method allows bidirectional data transfer via a three-conductor cable consisting of signal ground, receive input
and transmit output. It is recommended for communication distances less than 50 feet between the computer termi­nal and the instrument. Note: Multiple instruments cannot be connected to the same port.

The RS232 port is optically isolated to eliminate ground loop problems. Typically, “Data Out” of the computer/
terminal connects to the “RCV” terminal. “Data In” connects to the “XMT” terminal. If shielded cable is used, it
should be connected to the frame ground at one end only. Signal ground is to be connected at appropriate ground
terminals (refer to wiring diagram on bottom of this page).

RS-485

The RS485 multipoint capability allows up to 32 controllers to be connected together in a half-duplex network or up
to 100 controllers with an appropriate communications repeater.

This method allows bidirectional data transfer over a twisted pair cable. The twisted pair cable is a transmission line;
therefore, terminating resistors are required at the most distant ends of the line to minimize reflections (typically 120
ohms at each end). The RS485 circuit is fully optically isolated, eliminating ground loop problems. Parallel drops
from the transmission lines should be kept as short as possible; however, the line may be daisy-chained at each
controller. The polarity of the line is important and each device will specify an “A” (+) and “B” (-) connection.

Figure 1. Wiring diagram for digital communications.

Three remote communications options are available for the CN8240/CN8260 which allow interfacing to remote
devices utilizing the most common industry standards: RS232 and RS485.

Call factory for a recommended RS485 converter.

5

CN8240 & CN8260 Series Communications & Options

Digital
Communications Option

Omega+ Protocol

The Omega+ Protocol provides an easy way to query and modify controller parameters using a personal computer
and the optional digital communications option of the 18C/25C.

In this manual, the word “host” refers to the personal computer that’s communicating with the controllers in the
serial link, and the word “slave” refers to the controllers themselves.

All transactions between the host and the slaves are done with messages consisting of only printable ASCII charac­ters. There are only two primary types of messages: Requests and Responses. Messages coming from the host are
called requests and messages coming from the slaves are called responses.

With the exception of a broadcast request, for every request sent from the host, the slave will send back a response.
If a slave does not respond within 100 milliseconds, then the request can be considered lost.

A broadcast request is a request having an ID of ‘00’ (see Message Formats below). It is used to address all slaves
on the network. All slaves on the network will perform the actions requested in a broadcast message. However, a
response message will not be returned. Therefore, the host can only broadcast Write or Auxiliary Command
Requests. All slaves will ignore all Read Broadcast Requests.

Message Formats

All Omega+ messages adhere to the general format of:

[START CHAR][ID][ZONE][TYPE][PARAM][ERROR][DATA][CHKSUM][END CHAR]

START CHAR

This is a single character which designates the start of the message. For a Request message, this character is the
ASCII ‘$’ and for a Response message, this character is the ASCII ‘%’.

ID

This is a two-character ID identifying the receiving controller. Controller IDs go from 1-255 inclusively and all slaves
in the network must have unique IDs. The ID number of ‘00’, when used in a request, designates a broadcast mes­sage that is used to address all controllers in the network. See the section Request Message for an explanation of the
broadcast message.

In order to represent 255 with just two ASCII characters, a number system known as the Message Code Numbering
System is used. In this system, the most significant digit is represented with the numbers 0-9 and the letters A-Z
and the least significant digit is represented with the numbers 0-9.

The numbers 0-9 have the same values as their decimal counterparts and the letters A-Z have the values of 100 - 50
inclusively in increments of 10.

Example:

Message Code Value = Decimal Value

00 0 + 0 = 00
99 90 + 9 = 99
A0 100 + 0 = 100
A2 100 + 2 = 102
B8 110 + 8 = 118
P5 250 + 5 = 255

Zone

This is a two character ID identifying the Zone number in multi-zone capable controllers. For the 18C/25C, this num­ber must be 01.

6

CN8240 & CN8260 Series Communications & Options

Digital
Communications Option

Type

This is a single character identifying the type of message. The following table lists the type characters for all messages.

TYPE character Message Type

R Read Request or Read

r Read Response Returning a Negative Result

W Write Positive Value Request and Response

w Write Negative Value Request and Response

A Auxiliary Command

For further information, see following sections on the different message types.

This is a two character, message specific, parameter ID. For a Read/Write Request or Response message, this
ID identifies the controller parameter. For an Auxiliary Command Request or Response message, this ID specifies
the command.

Code Description

0 No error.

1 Framing error.

2 Hardware error.

3 Parity error.

4 Bad character in the TYPE field.

5 Bad message. Message cannot be understood.

6 Bad checksum. The checksum received

7 Bad zone ID.

8 Bad auxiliary command ID. The auxiliary

9 Bad parameter ID. The parameter is not

A Bad data. Bad representation in the data field

B Attempt to write to a read only parameter.

C Cannot write to a parameter because it’s in use.

Response Returning a Positive Result

PARAM

ERROR

did not match the checksum of the message.

command is not supported in this controller.

supported in this controller.

or data is out of range.

7