Omega DRA-DCC-8 User Manual

User’s Guide

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DRA-DCC-8

DIGIT AL TO 8 CURRENT LOOP CONVERTER

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Contents

1. MOUNTING INSTRUCTIONS

2. REPLACING FUSES

3. ASSEMBLY

4. SUPPLY VOLTAGE

5. MODES OF OPERATION

5.1 0-20 or 4-20mA output current selection

5.2 Switch Settings

6. PARALLEL CONTROL MODE

6.1 PLC Interface

6.2 The "E" (ENABLE) Terminal

7. SERIAL CONTROL MODE

7.1 RS232c / RS422 Select

7.2 RS422 Termination

7.3 Serial Control Switch Settings

7.4 Serial Communication Parameters

7.4.1 Baud Rate Select

7.4.2 ID Code

7.4.3 Command Formats

8. SELF TEST MODES

8.1 Self Test # 1

8.2 Self Test # 2

8.3 Self Test # 3

9. MULTIDROP CONFIGURATION

10. PUTTING THE UNIT INTO OPERATION

11. CALIBRATION

12. SPECIFICATIONS

1

1. MOUNTING INSTRUCTIONS

The DRA-DCC-8 is designed for standard DIN rail mounting.
Place the unit on the upper part of the mounting rail with the fastening tab facing

down. Using a suitable flat screwdriver loosen the tab slightly and attach the unit
to the rail. Once the tab is loosened, ensure that the unit is fastened securely in
place.

2. REPLACING FUSES

In order to replace a blown fuse, the unit has to be disassembled, as follows:
a. Take off both terminal strips by removing the four screws at the edges.

Note: This does not require disconnecting the cables connected to the strips.

b.

Remove the front panel using a suitable flat screwdriver. Press down gently on

the plastic springloaded tabs located in the slots either side of the unit.
c. Disconnect the flat connector which couples the LED circuit on the front panel.
d. Replace the blown fuse.

WARNING: Never install a fuse rated more than 800mA

3. ASSEMBLY

The DRA-DCC-8 unit includes
two printed circuit cards
designated as P.N 7041 and
P.N 7040. The two printed
circuit cards should occupy
the slots in the enclosure
according to fig 1.

Insert the two printed cards into their slots. Connect the flat cable between them.
Connect the front panel flat cable. The panel must be inserted into the grooves on
both sides of the case while pressing down until a distinct "click" is heard. Assembly
is completed by laying the terminal strips in place.

Figure 1

Note: The terminal strips are polarized and must not be placed backwards.

2

4. SUPPLY VOLTAGE

The DRA-DCC-8 is powered by a DC power supply at a range of 15-32Vdc. In order
to determine the minimum supply voltage, use the following equation:

Vmin = 8 + Rload(
where:
Vmin is the minimum required supply voltage.

Rload(

Ω) is the maximum output load including the leads resistance.

Ω) * 0.02

Note: If Vmin turns to be less than 15V, the minimum required voltage
should be 15 Vdc.

5. MODES OF OPERATION

The DRA-DCC-8 unit can be operated in several modes, determined by an internal
array of 8 DIP switches as follows:

4-20 or 0-20mA output current mode
Parallel control mode
Serial control mode
Self test mode

5.1 0-20 OR 4-20mA OUTPUT CURRENT MODE

Two current output spans are available: 4-20mA or 0-20mA selected by SW6.
The DRA-DCC-8 receives 12 bits of data which determine the output current value.
A channel data value of 4095 (FFF) is always interpreted as a 20mA output current.
A channel data value of 0 (000) will produce a 0mA output current when SW6
is OFF, or 4mA when ON.

5.2 SWITCH SETTINGS
Parallel Control Mode

MODE

0-20mA
4-20mA

S1 S2 S3 S4 S5 S6 S7
OFF OFF OFF OFF
OFF OFF ON OFF

XXX
XXX

3

Serial Control Mode

BAUD RATE (BPS)

300

4800
9600

19200

SW5 MSB

S1 S2 S3 S4 S5 S6 S7

OFF OFF

OFF

OFFONON

UNIT ID CODE

ONON

Self Test Mode

MODE

SELF TEST#1
SELF TEST#2
SELF TEST#3

* according to para #5.2

S1 S2 S3 S4 S5 S6 S7

ON OFF X OFF

OFF ON OFF

ON ON OFF

6. PARALLEL CONTROL MODE

ON=4-20mA

OFF=0-20mA

X
X

X

ON
ON
ON
ON

*
*

MODE

PARALLEL MODE

* according to para #5.2
In the parallel control mode, the DRA-DCC-8 unit is controlled via a 15 bit bus.

Three Address bits (A0-A3) select the proper current output channel and 12 Data
bits (D0-D11) determine its value (A0 and D0 are MSB). The DRA-DCC-8
microprocessor continuously scans the input vector (Address + Data) terminals
and updates its memory tables upon recognizing a new vector. The unit is
asynchronous in nature. The data should be valid for at least 160 microseconds.

S1 S2 S3 S4 S5 S6 S7

OFF OFF * OFF

X

SINK

SOURCE

6.1 PLC INTERFACE

The PLC's output modules can be divided into
three popular types; TTL output module, 24Vdc
sink type and 24Vdc source type.
There is a jumper selector on printed circuit card
PN 7040 which selects between Sink/Source
input. (TTL output module should usualy be
considered as sink type). See figure 2.

4

Figure 2.

6.2 THE "E" (ENABLE) TERMINAL

For E="1" the unit is enabled, which means that all input vectors are received and
the output is updated. When E="0" the unit ignores any new input vector. The E
terminal is recommended to be used as a strobe for parallel data which has a long
setup time. In this case the following sequence is recommended: prior to applying
a new vector, the E terminal should be set to logical 0 (inhibit state), then the new
input vector should be imposed. Once the new data is set, the E terminal should
be pulsed.
The E terminal is also used for multidrop configuration. The 15 bit vectors are
applied to the units in parallel and the selection is carried out by controlling the
"E" inputs.

7. SERIAL CONTROL MODE

7.1 RS232c / RS422 SELECT

he DRA-DCC-8 is equipped with two serial
communication ports: The RS232c and the
RS422. A jumper switch at the right side of the
DIP switch array is used to select the required
communication type. See figure 3.

RS-422

7.2 RS422 TERMINATION

The SW8's ON state terminates the RS422 receiver terminals with a 100W load.
In a multidrop configuration, the last (most distant) DRA-DCC-8 unit should be
terminated in order to match the transmission lines.

Figure 3.

RS-232c

Note: Only one termination load per RS422 communication link is permissible.

7.3 SERIAL CONTROL SWITCH SETTINGS

S1 S2 S3 S4 S5 S6 S7

BAUD RATE ID CODE * ON

* according to para #5.2

7.4 SERIAL COMMUNICATION PARAMETERS

The communication protocol is 8 bit ASCII, even parity, and one stop bit.

5

7.4.1 BAUD RATE SELECT

SW1 and SW2 select one out of four available baud rates.

SW1 SW2

300 BPS
4800 BPS
9600 BPS

19200 BPS

OFF

OFF

ON OFF

OFF ON

ON ON

7.4.2 ID CODE

Up to eight DRA-DCC-8s can be connected in a multidrop configuration. Switches
SW3, SW4, and SW5 (MSB) set the ID code.

7.4.3 COMMAND FORMATS
Three types of command formats are available:

Without echo back
acknowledgment.

With echo back
The host computer sends a message and receives an acknowledgment stating
the DRA-DCC-8 ID number and the addressed channel number.
Status report

The host computer sends a massage and does not receives an

7.4.3.1. WITHOUT ECHO BACK FORMAT

[A] [ID CODE] [CHANNEL VALUE] [CR]

The character A begins the command block.

The second byte is the ID code (07). The third byte is the addressable channel
number (07). Up to four bytes of a channel's value can be in BCD mode (0-4095).
Leading zeroes can be omitted. The last byte is [CR] which must terminate the
command block.

7.4.3.2. WITH ECHO BACK FORMATS

[C] [ID CODE] [CHANNEL VALUE] [CR]
This format differs only in the opening character. After every command block

transfer, the DRA-DCC-8 echoes back the following:

6

[C] [ID CODE CHANNEL] [LF] [CR]

Note: If the value is omitted it will be treated as zero. Separators such as
blanks or commas are not allowed.

Example:
Channel 4 in DRA-DCC-8 no. 7 has to receive the value of 981. Echo back is required

The command format is:
[C] [7] [4] [981] [CR]

The echo back will be: C 7 4

Note: The channel numbers on the DRA-DCC-8 front panel are designated
from 1 to 8, in binary they are designated from 0 to 7.

Note: When applying the echo back mode, it is advisable to wait for the
echo back before transmitting a new command.

7.4.3.3 STATUS REPORT FORMAT

[S] [ID CODE] [CR]
The addressed DRA-DCC-8 unit will respond with the values stored in its eight

channels. The response will start with S, ID code, following with eight channel
values separated with commas and [LF] [CR] as terminators.

Example:
DRA-DCC-8 unit number 3 has the following stored data: ch1: 300, ch2: 1270,

ch3: 0, ch4: 4087, ch5: 2099, ch6: 764, ch7: 3078, ch8: 550. The response from
the device will be:

S3,300,1270,0,4087,2099,764,3078,550 [LF] [CR].

Note: Wait until the status report has terminated before transmitting new
commands.

8. SELF TEST MODES

The DRA-DCC-8 is provided with three test modes.

MODE

SELF TEST#1
SELF TEST#2
SELF TEST#3

* according to para #5.2

S1 S2 S3 S4 S5 S6 S7
ON OFF X OFF
OFF ON OFF

ON ON OFF

X
X
X

*
*

7

8.1 SELF TEST #1 (Communication Ports T est)

In order to test the serial communication ports, this test mode converts the unit to
a transponder for ASCII characters. Any transmitted character will be echoed to
the host terminal. The host parameters should be set to:

Baud rate : 4800, Word length: 8 bits, Parity: even, Stop bit: 1

8.2 SELF TEST #2 (Same Leve)l

In this test mode, the DRA-DCC-8 unit ignores the address field. All the outputs
are set according to the data field only.

8.3 SELF TEST #3 (Saw Tooth)

In this test mode, only one output channel (according to the address setting) will
produce a saw tooth wave form in which the whole value range is used.

9. MULTIDROP CONFIGURATION

Up to eight DRA-DCC-8 units can be installed in a multidrop configuration using
the RS422 communication port.

The controller's RS-422 transmitter is connected to the units' receivers while the
controller's RS-422 receiver is connected to the units' transmitters.

As the communication cable might be several thousand feet long, it is necessary
to terminate the end of the line with its characteristic impedance in order to avoid
reflections in the transmission line causing data distortion. SW8 in its ON state
terminates the Rx inputs with a 100Ω load.

10. PUTTING THE UNIT INTO OPERATION

The DRA-DCC-8 is supplied with a set configuration for parallel control mode.
The DIP switch setting is:

MODE

PARALLEL 4-20mA

The communication port selector (see para #7.1) is set to RS232C.
The unit should be set up according to the required configuration.
Before applying voltage to the unit see para #4 for power supply consideration.

8

S1 S2 S3 S4 S5 S6 S7

ONOFF OFFOFF OFF OFF OFF

The channel LEDs are connected in series with the output current so that they will
light only as an indication of a closed current loop.

Note: After every power on, the unit is reset and the initialized
default output currents are according to the SW6 setting
(see para #5.2).

In the parallel control mode, internal pull-up resistors on each of the input terminals
keep them in logical 1 state. The unit will recognize input voltage up to 0.5V as
logical 0 and voltages from 4V to 60V as logical 1.

11. DRA-DCC-8 CALIBRATION

Generally there is no need to calibrate the DRA-DCC-8 unit. However if calibration
is required, the following steps should be carried out: Two potentiometer trimmers,
one for "Zero" and the other for "Span" are located on printed card 7040. The
trimmer close to the card edge is the "Zero". Use the following switch setup for
switching all the outputs between 4 and 20mA

MODE

ALL CH. = 4mA

ALL CH. = 20mA

Note: Set the unit to sink mode (fig.2).

Step 1:
Select one channel (for example ch.#1) for the initial tuning. Set the DIPswitch array

to "all 4mA".
Apply supply voltage to the unit. The initial state of all the output currents is 4 mA.
Use SW2 to switch all the outputs between 4 and 20mA. Iteratively set the "Zero"
and the "Span" trimmers for 4.00mA and 20.00mA.

S1 S2 S3 S4 S5 S6 S7

XX

ONOFF ON OFF

XXX

ONOFF OFFOFF X

Step 2:
Monitor all the 8 channels in 4mA state, and calibrate the Zero trimmer so that

their average readings is 4.000mA.
Then repeat for 20mA state, and calibrate the Span trimmer so that their average
readings is 20.000mA. This procedure should be repeated until calibration is
satisfactory.

9

12. SPECIFICATIONS

INPUTS:
PARALLEL INPUTS

LOGIC LEVELS:
DATA HOLD TIME:
MAXIMUM PARALLEL INPUT RATE:
SERIAL COMMUNICATION

BAUD RATES:
PARITY:
STOP BIT:
STATUS REPORT:
MULTIDROP CAPABILITY:
OUTPUTS:

OUTPUT CURRENT SPAN:
OUTPUT CURRENT SETTLING TIME:

POWER SUPPLY:
CURRENT CONSUMPTION:
MAXIMUM LOOP RESISTANCE:
ACCURACY:
RESOLUTION:
INDICATORS:

AMBIENT TEMPERATURE
Operation:
Storage:

RELATIVE HUMIDITY:
HOUSING

Box:
Terminals:

MOUNTING:
FUSE:
WEIGHT:
DIMENSIONS:

Parallel & Serial control inputs
3 - Output current loop address
12 - Output current value (Data)
1- Enable (E)

0<"0"<0.5V, 4 <"1"< 60V
160 microsecond
6000 updates per second
RS232c full duplex

RS422 full duplex
300, 4800, 9600, 19200 BPS
Even
One
Reports as interrogated
Up to eight units
8 continues current loops

0-20mA or 4-20mA (user selected)

4.2 ms max. for 99% of step
15-32 Vdc (regulated)
85mA max.

According to Rmax(K

±

0.1% of span typical, ±0.2% of span max.

0.025% of span typical,0.05% of span max.
Yellow Power On LED

8 Red output channel LEDs

-10 to 60 oC (14 to 140 oF)

-25 to +85 oC (-13 to 185 oF)
5 to 95%, non condensing
Plastic Polycarbonate

According to IP 50 DIN 40050

Standard DIN rail
630mA fast blow (5x20mm)

0.7Kg (1.5 lb.)

73.2H x 200W x 121mmD (2.88"x7.88"x4.76")

Ω

)= (Vsupply -6)/20

According to IP 20 DIN 40050

10

OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship
for a period of 13 months from date of purchase. OMEGA Warranty adds an additional one (1) month
grace period to the normal one (1) year product warranty to cover handling and shipping time. This
ensures that OMEGA’s customers receive maximum coverage on each product. If the unit should malfunction,
it must be returned to the factory for evaluation. OMEGA’s Customer Service Department will issue an Authorized
Return (AR) number immediately upon phone or written request. Upon examination by OMEGA, if the unit is
found to be defective it will be repaired or replaced at no charge. OMEGA’s WARRANTY does not apply to defects
resulting from any action of the purchaser, including but not limited to mishandling, improper interfacing,
operation outside of design limits, improper repair, or unauthorized modification. This WARRANTY is VOID if
the unit shows evidence of having been tampered with or shows evidence of being damaged as a result
of excessive corrosion; or current, heat, moisture or vibration; improper specification; misapplication; misuse
or other operating conditions outside of OMEGA’s control. Components which wear are not warranted, including
but not limited to contact points, fuses, and triacs.

OMEGA is pleased to offer suggestions on the use of its various products. However,
OMEGA neither assumes responsibility for any omissions or errors nor assumes
liability for any damages that result from the use of its products in accordance
with information provided by OMEGA, either verbal or written. OMEGA warrants
only that the parts manufactured by it will be as specified and free of defects.
OMEGA MAKES NO OTHER WARRANTIES OR REPRESENTATIONS OF ANY KIND
WHATSOEVER, EXPRESSED OR IMPLIED, EXCEPT THAT OF TITLE, AND ALL
IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. LIM ITATION
OF LIABILITY: The remedies of purchaser set forth herein are exclusive and the
total liability of OMEGA with respect to this order, whether based on contract,
warranty, negligence, indemnification, strict liability or otherwise, shall not exceed
the purchase price of the component upon which liability is based. In no event
shall OMEGA be liable for consequential, incidental or special damages.

CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic
Component” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medical
applications or used on humans. Should any Product(s) be used in or with any nuclear installation or activity,
medical application, used on humans, or misused in any way, OMEGA assumes no responsibility as set forth
in our basic WARRANTY / DISCLAIMER language, and additionally, purchaser will indemnify OMEGA and
hold OMEGA harmless from any liability or damage whatsoever arising out of the use of the
Product(s) in such a manner.

Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department.
BEFORE RETURNING ANY PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED
RETURN (AR) NUMBER FROM OMEGA’S CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID
PROCESSING DELAYS). The assigned AR number should then be marked on the outside of the return
package and on any correspondence.
The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent
breakage in transit.

FOR WARRANTY RETURNS, please have the
following information available BEFORE contacting
OMEGA:

1. P.O. number under which the product was
PURCHASED,

2. Model and serial number of the product under
warranty, and

3. Repair instructions and/or specific problems
relative to the product.

OMEGA’s policy is to make running changes, not model changes, whenever an improvement is possible.
This affords our customers the latest in technology and engineering.
OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
© Copyright 1996 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied,
photocopied, reproduced, translated, or reduced to any electronic medium or machine-readable form, in
whole or in part, without prior written consent of OMEGA ENGINEERING, INC.

WARRANTY/DISCLAIMER

RETURN REQUESTS / INQUIRIES

FOR NON-WARRANTY REPAIRS, consult
OMEGA for current repair charges. Have the
following information available BEFORE
contacting OMEGA:

1. P.O. number to cover the COST
of the repair,

2. Model and serial number of product, and

3. Repair instructions and/or specific
problems relative to the product.

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