Acromag BusWorks 900MB Series User manual

BusWorks900MB Series
Modbus/RS485 Network I/O Modules
Model 942MB
Dual Frequency or Pulse Counting Input Module
USER’S MANUAL
ACROMAG INCORPORATED Tel: [phone]
30765 South Wixom Road Fax: [phone]
Wixom, MI 48393-2417 U.S.A.
Copyright 2002, Acromag, Inc., Printed in the USA.
Data and specifications are subject to change without notice. 8500682H

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
2
IMPORTANT SAFETY CONSIDERATIONS
You must consider the possible negative effects of power, wiring,
component, sensor, or software failure in the design of any type of
control or monitoring system. This is very important where property
loss or human life is involved. It is important that you perform
satisfactory overall system design and it is agreed between you and
Acromag, that this is your responsibility.
GETTING STARTED
MOUNTING AND DIMENSIONS………………………
3
CONTROLS………………………………………………
3
ISOLATION BARRIERS..……………………………….
3
CONNECTIONS……………………………………….
4
Power……………………………………………..
4
Input…………………………………………………
4
Network…………………………………………..
6
Output…………………………………………….
6
Earth Ground..…………………………………….
7
CONFIGURATION SOFTWARE……………………….
8
Installation……………………………………….
8
Starting The Program…………………………….
9
Creating A Configuration File…………………..
10
Input Setup………………………………………
11
Alarm Configuration…………………………...
13
Writing Your Configuration............................
14
Printing Your Configuration...........................
14
Saving Your Configuration.............................
14
Testing Your Module……………………………..
15
Input Calibration………………………………..
16
TROUBLESHOOTING………………………………..
17
TECHNICAL REFERENCE
KEY FEATURES………………………………………
19
HOW IT WORKS………….……………………………..
20
CONFIGURATION TERMS & DEFINITIONS……...
21
REGISTER MAP…………………………………………
24
Data Types…….…………………………………..
33
SPECIFICATIONS…………………………………….
33
Model Number…………………………………..
33
Default Factory Configuration………………….
34
Inputs…..…………………………………………
34
Digital Outputs (SSR’s)..……………….………..
36
Enclosure/Physical……………………………….
36
Agency Approvals…………………….....……….
36
Environmental…………………………………..
36
Communication Interface……………………..
38
Controls & Indicators…………………………….
39
ACCESSORIES………………………………………….
39
REVISION HISTORY...................................................
40
Windows® is a registered trademark of Microsoft Corporation.
Modbus® is a registered trademark of Modicon, Incorporated.
TABLE OF
CONTENTS
Symbols on equipment:
Means Refer to User’s Manual
(this manual) for additional
information”.
The information of this manual
may change without notice.
Acromag makes no warranty
of any kind with regard to this
material, including, but not
limited to, the implied
warranties of merchantability
and fitness for a particular
purpose. Further, Acromag
assumes no responsibility for
any errors that may appear in
this manual and makes no
commitment to update, or
keep current, the information
contained in this manual. No
part of this manual may be
copied or reproduced in any
form without the prior written
consent of Acromag, Inc.
!

BusWorks942MB Module User’s Manual Dual Frequency Input
___________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
3
TB1
12
FIN 0
13
44
15 16
41 36 33
TB4
FRTN
FIN 1 RTN
FRTN OUT0
COM
D D A
TB3
11
NC
46
14
NC
4345 42
OUTPUTS
35 3234
NETWORK
31
INPUTS
OPTICAL
OUT1
DIGOUT
OPTICAL
TB3
B
COM
RS485
TB1
FREQUENCY INPUT0,1
TRANSFORMER
TRANSFORMER
PWR
PWR
TB4
942MB-0900
ISOLATION
DIAGRAM
0
DFT
ST
NC NC
R11
46 45
14
43
OUT1
42 35
COM
34
B
32 31
TB1
1
Acromag
TB4
(PLUG-IN TYPE) TB1
TB4 TB3
RU N
TB1
12
FIN 0
15
FIN 1
13
FRTN
TB4
44
RTN
16
FRTN
41
TB3
36
D
OUT0
COM
33
A D
PWR
FREQUENCY INPUT 0,1
RUN/PWR LED (GREEN)
TERMINALBLOCKS
REMOVABLE
OUTPUTLED (YELLOW)-
ON WHEN OUTPUTS ARE
CONDUCTING.
DIG OUT
DEFAULTMODE SWITCH -
PUSH FOR DEFAULTMODE.
STATUS LED FLASHES IN
DEFAULTMODE.
STATUS LED WILLFLASH
RAPIDLY UPON WATCHDOG
TIMEOUT.
STATUS LED (YELLOW)
RS485
C
0
DFT
ST
D A
L
2.34
R
(95.3)
11 12
FIN 0
45
14 15
FIN 1 RTN
42
TB3
34 31
(118.9)
(26.7)
1
Acromag
NC
(99.1)
TB1
NC
DIG OUT
TB4
RS485
B D
TB3
(59.4)
1.05
RUN
3.75
TB1 TB4
46
3.90
FRTN
13 16
FRTN
44
OUT1
41
OUT0
43
(110.5)
4.35
36
COM
33
COM
35 32
4.68
PWR
"T"RAILDIN MOUNTING
DIN EN50022,35mm
NOTE: DimensionsAreINCHES (MILLIMETERS).
FREQUENCY INPUT 0,1
MOUNTING AND
DIMENSIONS
Unit mounts to “T” type DIN
rails (35mm, type EN50022).
Units may be mounted side-
by-side on 1-inch centers.
WARNING: IEC Safety
Standards may require that
this device be mounted within
an approved metal enclosure
or sub-system, particularly for
applications with exposure to
voltages greater than or equal
to 75VDC or 50VAC.
CONTROLS
Green Run LED will stay ON if
power is on and unit is OK and
will blink if unit fails.
Yellow ST LED will blink slowly
if module is in Default Mode.
This LED will blink quickly for a
watchdog timeout and will stay
ON if any channel is open or
over-range.
Yellow Output LED’s will turn
ON if output switch is closed.
Push the DFT button to place
module in Default Mode (ST
LED will blink). This sets unit
to 9600 baud, address 247,
and no parity.
ISOLATION BARRIERS
Dashed Lines denote isolation
barriers.
The inputs, outputs, network,
and power circuits are isolated
from each other for safety and
noise immunity.

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
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4
2
0
RUN
R
3
1
ST
T
NC
FIN0
11 12
FRTN NC
FIN1
13 14 15
RTN
OUT1
FRTN
16
OUT0
D
COM COM
PW R
D B A
NC
FIN0
11 12
NC
FIN1
14 15
DI G O UT
RTN
OUT1
RS485
D
COM
PW R
B A
T T
T
NC
11
36
NC
FIN0
FRTN
11 12 13
NC
12 13 14
35 34 33
NC
FIN1
FRTN
14 15 16
DI G O UT
RTN
OUT1 OUT0
15 16
32 31
COM
36 35
RS485
D D
COM
34 33 32
PW R
B A
31
NC
FIN0
11 12
NC
11 12
36 35
NC
FIN1
14 15
RTN
OUT1 NC
14 15
33 32
D
COM
35 34
PW R
B A
PW R
32 31
DFT
36 35 34 33 32 31 36 35 34 33 32 31 36 35 33 32 35 34 32 31 36 35 34
FIN0
FRTN
OUT1
33 32 31
FIN1
FRTN
RTN
OUT0
36
100
COM COM
35 34 33
D D B
32 31
A
36 35
FIN0
33 32
FIN1
OUT1
RTN
35 34
COM
D
32 31
B A
DI G I TAL
O UTPUTS
RS485
FRTN
FRTN
13 16
OUT0
COM
(SEE NOTE)
D
NODE 2'
R R
RS485 PW R
100
FRTN
FRTN
13 16
DI G O UT
OUT0
COM
(SEE NOTE)
13 16
FREQ UENCY I NPUT 0 , 1
DI G O UT
34 31 36
100
D
NODE 4
33
120 RDIGITAL
OUTPUTS
61
100
FREQ UENCY I NPUT 0 , 1
31
34 31 36
100
RS232
33
RS485
RS485SIGNAL
REPEATER
R
RS485
RS485
NODE 2
FREQ UENCY I NPUT 0 , 1
3
34 31 36
100
FRTN
FRTN
2
OUT0
COM
(SEE NOTE)
33
D
NODE 3
DI G O UT
NODE 32'
POWER
RS485
NODE 31
(SEE NOTE)
FREQ UENCY I NPUT 0 , 1
DI G O UT RS485
ANALOGINPUT
FREQ UENCY I NPUT 0 , 1
Ac ro m a g
(SEE NOTE)
TERMINATION
RESISTOR
MODBUS MASTER -A HOST
PCRUNNINGAPPLICATION
SOFTWARE.
NODE 1' NODE 32
ACROMAG4SCR-TTM-1
OREQUIVALENT
NODE 1
ACROMAG4SCC-TTM-1
OREQUIVALENT
RS232-TO-RS485
INTERFACE
CONVERTER
FREQ UENCY I NPUT 0 , 1
30
1
(SEE NOTE)
RS485DIFFERENTIALPAIR
SEGMENT1 (UP TO4000FEET, UP TO 32 NODES PER SEGMENT)
SEGMENT2 (UP TO4000FEET,
UP TO 32 NODES PER SEGMENT)
MODBUSRS485NETWORK
NOTE (Earth Ground):PerEIA 485guidelines,a 0.5W,100ohmresistoris connectedbetweenearthgroundandtheportcommon
tolimitcirculatinggroundcurrents,particularlyoverlongdistanceswithmultipleconnectionstosafetyground.Thisresistorisnot
requiredtoachieveoperation,butrecommendedasgoodwiringpractice. Ifmodulesaredistributedwithincloseproximityata
location,thenport commons mayconnecttogetherviaathirdlinewithoutthe100ohmresistor.
A network segment may contain up to32 nodes without theuseofa signal repeater.
Transmissiondistanceisupto4000feetpersegmentwithoutarepeater.
A 120ohmtermination resistormustbeplaced at bothendsof anetwork ornetwork segment.
The total number of nodes andtotal distancemay beextendedbyusingsignal
repeater(s), suchastheAcromag4SCR-TTM-1. Themaximumnumberofmodules
possibleis furtherlimitedbytheaddressrangefrom1to246.
✓Connect 12-36V DC or 24VAC to the non-polarized power terminals
labeled A & B. For supply connections, use No. 14 AWG wires rated for
at least 75C. CAUTION: Do not exceed 36VDC peak power voltage.
TB3
D
D
A
B
RS485 PWR
36 34 33 31
EARTH
GROUND
35 32
TB3
COM
COM
INPUTPOWER
ISISOLATED
10 TO 36VDC
OR 24VAC
NON-POLARIZED
CAUTION: Risk of Electric Shock –More than one disconnect switch may
be required to de-energize equipment before servicing.
✓Connect Frequency or Pulse signal to the input terminals FIN & FRTN.
Refer to the examples below for connections to other types of inputs.
-
+
14 11
NC
NC
1516 1213
TB1
FREQUENCY INPUT 0,1
TB1
SHIELDED
CABLE
RTN RTN
BIPOLAR
BIASTO+VFREQUENCY
GENERATOR
SETMODULETOUNIPOLAROR
BIPOLARINPUTASREQUIRED
FRTN
FIN 1
UNIPOLAR
BIASTOGND
FRTN
FIN 0
+V
INTERNAL
CONNECTIONSTORTN
CAUTION: Do not connect internal pull-up or pull-down resistors for
voltages greater than 11V peak, or damage to the circuit may result.
CONNECTIONS
Example Modbus System
Connections.
IMPORTANT –External
Fuse: If unit is powered from
a supply capable of delivering
more than 1A to the unit, it is
recommended that this current
be limited via a high surge
tolerant fuse rated for a
maximum current of 1A or less
(for example, see Bel Fuse
MJS1).
Power
Voltage
Current
10VDC
135mA
12VDC
110mA
15VDC
90mA
24VDC
60mA
36VDC
45mA
24VAC
100mArms
Input Connections
Connection to a standard
frequency generator.
To prevent measurement
error, limit maximum input
frequency to less than
110% of full-scale.
Limit signal amplitude to
±200V peak (disconnect
internal pullup/ pulldown
connections above 11V).

BusWorks942MB Module User’s Manual Dual Frequency Input
___________________________________________________________________
______________________________________________________________________________________
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5
16 13
+V +V
15 14 12 11
OR
TB1
FRTN
FRTN
FRTN
TB1
1K
NC
FIN 1
NC
FIN 0FIN 0
FREQUNCY INPUTS 0,1
HIGH-SIDE
SWITCH
ENA UNIPOLAR
(BIAS TOGND)
ENABLE PULL-
DOWN TO GND
INTERNAL
CONNECTIONS
OPEN COLLECTOR
OR OPEN DRAIN
SETMODULE TOUNIPOLAR
INPUTAND ENABLE PULL-DOWN
SHIELDED CABLE
14 11
NC
NC
1516 1213
TB1
FREQUENCY INPUTS 0,1
2.7K
+5V
FIN 1
FRTN
FIN 0
FRTN
FIN 0
FRTN
OR
TB1
LOW-SIDE
SWITCH
SETMODULE TOUNIPOLAR
INPUTAND ENABLE PULL-UP
ENA PULL-UP
TO+5V
INTERNAL
CONNECTIONS
OPEN
COLLECTOR
OR DRAIN
ENA UNIPOLAR
(BIAS TOGND)
SHIELDED CABLE
FRTN
FIN 0
2.7K
TB1
16 13
TB1
1415 1112
FREQUENCY INPUTS 0,1
+5V
FRTN
FRTN
SeeNOTE
NC
FIN 1
NC
SHIELDEDCABLE
FIN 0
SET MODULE TOUNIPOLAR
INPUT ANDENABLE PULL-UP
ENAUNIPOLAR
(BIASTOGND)
ENAPULL-UP
TO+5V
DRYCONTACT
INTERNAL
CONNECTIONS
2.7K
FIN 0
FRTN
TB1
14 11
+5V
16 13
15 12
TB1
FREQUENCY INPUTS 0,1
SeeNOTE
NC
NC
SHIELDEDCABLE
SET MODULETOUNIPOLAR
INPUT ANDENABLE PULL-UP
FRTN
FIN 0
FRTN
FIN 1
TTLLOGICLEVELS ENAPULL-UP
TO+5V
INTERNAL
CONNECTIONS
ENAUNIPOLAR
(BIASTOGND)
For low-side transistor switches, use the on board pull-up resistor. For
high-side transistor switches, use the on board pull-down resistor.
15 12
16 1314 11
TB1
NC
NC
FRTN
FREQUENCY INPUTS 0,1
SeeNOTE FIN 1
FIN 0
TB1
SHIELDEDCABLE
+V
ENABIPOLAR
(BIASTO+V)
FRTN
FRTN
MAGNETIC
PICKUP
INTERNAL
CONNECTIONS
SET MODULETOBIPOLARINPUT
CONNECTIONS
Input Connections
Connection to high-side
switches.
Connection to low-side
switches.
Connection to dry-contact
relays.
Connection to TTL logic
signals.
Connection to magnetic
pickups.

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
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6
✓Connect the RS485 terminals to your network. Differential data lines
may use twisted pair. The 100 ohm resistor shown between port
common and earth ground may be eliminated for modules in close
proximity to one another.
36 34 33 31
35 32
100 OHM
TB3
TB3
COM
D
D
A
DROP-LINE
COM
RS485
B
PWR
COM
DATA
DATA
HALF-DUPLEX
RS485 NETWORK
TO OTHER
NETWORK
MODUES
NETWORK
IS ISOLATED
A 0.5W, 100 OHM RESISTOR IS CONNECTED
BETWEEN EARTH GROUND AND PORT COMMON
PER EIA 485 STANDARD.
D D
46
13
44 43
16
41
21
36
24
D
33
12
45
15
42
21 23
D
34
24 26
31
Tx
TB1 TB4
IN0+ OUT2 IN1- OUT0
COM
D
IN2-
D
TB1
CH 0 CH11
CH 3 CH 8
TB2
TB2
EXC2
CH 5
D
RTN
COM
11 12 1514
45 42
22 23
D
35 34
2625
B A
3132
11 1413
D IG ITA L IN or O U T
46 44 43
22
36 35
25
32
COMRx
IN0- IN1+
C JC -0
RTN
OUT3
RTN
OUT1
TB1
TB2
IN2+
C JC -1
TB3
COM
R S 4 85
TB4
COM
TB2
IN3+ IN3-
TB3
CONNECT
POWER
EXC1
CH 1 CH 2 CH 9
CH10
RTN
CH 4
TB4
COM COM
COM
TB4
D
CH 7
TB3
TB3
P W R D IG ITA L I/O R S 4 85 P W R
SETBAUDRATE
16
D IG ITA L IN or O U T
D
41 33
CONNECTTOACPOWER
PCRUNNING
MODBUS
APPLICATION
SOFTWARE
PERSONALCOMPUTER
MASTER-
OPTIONAL120OHM
TERMINATIONRESISTOR
SETBAUDRATE
ANDPARITY
IN P U TS 0 ,1 IN P U TS 2 ,3
MODEL924MB-0900
TB1
RTN
CH 6
MODEL906MB-0900
EXC3
CONNECT
POWER
TOADDITIONAL
MODULESOR
OTHERRS485
NETWORKDEVICES
RS232
PORT
D IG ITA L O U TP U TS
SETBAUDRATE,PARITY,
ANDADDRESS SETBAUDRATE,PARITY, ANDADDRESS
RS485NETWORK-HALFDUPLEX
ANYRS232-TO-RS485CONVERTER
(ACROMAGMODEL4SCC-TTM-XSHOWN)
SERIES9XXMB NETWORK CONNECTIONS
SEENOTE REGARDINGPORTCOMMONANDEARTHGROUNDCONNECTIONS.
NOTE (EARTHGROUND): PORTCOMMONS ARE SHOWNCONNECTINGVIAA THIRD
WIRE. ACONNECTIONTOEARTHGROUNDSHOULDALSOBE PROVIDEDATONE
POINTALONGTHENETWORK. THIS ISACCEPTABLEFORMODULESLOCATEDIN
CLOSEPROXIMITYTOONEANOTHER,BUTNOTRECOMMENDEDFORMODULES
DISTRIBUTEDOVERLONGDISTANCES.
PEREIA485STANDARD,ITIS GOODPRACTICETOINSTEADCONNNECTPORT
COMMONTOEARTHGROUNDVIAA 0.5W,100OHMRESTORATEACHPOINTALONG
THENETWORK,PARTICULARLYFORNETWORKS THATPROVIDE MULTIPLE GROUND
CONNECTIONSDISTRIBUTEDOVERLONGDISTANCES.
1 - 3 00 5 - 4 8 00
2 - 6 00 6 - 9 6 00
3 - 6 00 7 - 1 9 .2K
4 - 2 40 0 8 - 3 8 .4K
P OW ER
BAUD
RATE
acromag
TB 1 RS-232 C
AC INPUT
COM
TB 2 RS-485
R RT
Rx
Tx
24 VDC
D D
COM
T
24 VDC
RTN
S1 2 3 2 >
4 8 5
7654321 8
R S4 8 5
F A UL T 4 8 5 > 2 3 2
✓Connect solid-state output switches.
V
46 45 43 42
RTN
D L
44 41
TB4
DIGOUT
TB4
OUT1
R
OUT0
SHIELDED CABLE
EARTH GROUND
OUT0
OUT1
SOLID-STATE OUTPUT SWITCHES
ARE RATED TO 48VDC AND 1A.
POSSIBLE VARIATIONS
DC APPLICATIONS ONLY
CONNECTIONS
Network
Port common COM should
connect to earth ground at
each node. A 100 ohm
resistor is shown connected
between earth ground and port
common per EIA 485 standard
to limit circulating currents.
This resistor is not required for
operation, but is good wiring
practice.
Refer to this drawing as an
example of connections to an
RS485 signal converter and
network.
The Acromag 4SCC-TTM-X
signal converter is shown
here.
Output
Outputs turn OFF (open)
following a software or power-
on reset of the module.
Optionally, outputs may be
sent to a defined state
following a watchdog timer
timeout.

BusWorks942MB Module User’s Manual Dual Frequency Input
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7
IMPORTANT –Add Protection With Inductive Loads: Outputs
already include internal reverse-bias shunt diodes to help protect the
switch from damage due to the reverse-bias voltages generated when
switching inductive loads. You should add external protection near the
inductive load to prevent these transients from being sent along the
connection wires. Place a diode (1N4006 or equivalent) across an
inductive load with the cathode to (+) and the anode to (-) as shown
above.
+
11
NC
46
12
45
14
NC
43
15
RTN
42 35
D
34
B
32
A
31
+
-
+
FIN 0
OUT1
FIN 1
TB3
COM
TB1
13 16
41
44
D
3336
NC
NC
RTN
OUT0
OUT1
TB4
FRTN FRTN OUT0
DIG OUT
COM
RS485 PWR
TB3
OR24VAC
10TO36VDC
NC
NETWORKCONNECTIONS (SEEDRAWING 4501-805)
DC/AC
POWER
DIODE
0-48VDC
FREQUENCY INPUT 0,1
DE-ENERGIZEDCONDITION. EARTHGROUND
(SEENOTE1)
SHIELDEDCABLE
DCRELAY
POWER
INPUT CONNECTIONS
(SEE DRAWING4501-904)
SHIELDEDCABLE
TB1
(SPST-NO)
TB4
DIGITAL I/O
EARTH
MODEL942MB-0900
EARTHGROUND
(SEENOTE1)
CONTACTPROTECTION
1N4006OREQUIVALENT
(SEENOTE2) GROUND
TYPICALDIN-RAILMOUNTEDRELAYIN
NON-POLARIZED
NOTE:ALLRELAYCONTACTSSHOWN.
NOTE1: RETURNSSHOULDBECONNECTEDTOEARTHGROUND
ATTHESAMEPOINTTOAVOIDCIRCULATINGGROUNDCURRENTS.
IMPORTANT-OBSERVEPROPERPOLARITY
INTERPOSINGRELAY CONNECTIONS
OUTPUTSINCLUDE
TRANSIENTAND
REVERSE SHUNT
PROTECTION
NOTE2: DIODEADDEDLOCALTOINDUCTIVELOADTOSHUNTTHE
REVERSE EMFTHATISGENERATEDWHENCURRENTTHROUGH
THEINDUCTOR(RELAYCOIL)ISTURNEDOFF.
LOCATERELAYNEARLOAD
TWOSOLID-STATE
OUTPUTSWITCHES
WITHCOMMONRETURN
RATEDTO48VDCAND1A
6
4 5
3
7812
✓Connect Earth Ground as indicated in the example drawings above.
The plastic module housing itself does not require earth ground.
The ground connections noted in the drawings are recommended for
best results and may be needed to meet EMC specifications. If sensors
are already grounded, use caution and avoid making additional ground
connections which could create ground loops.
Refer to this drawing if you
need to increase switching
capacity with another relay.
Earth Ground
Warning: To comply with
safety and performance
standards, use shielded cable
and connect earth ground as
noted. Failure to use good
wiring and grounding practices
may be unsafe and hurt
performance.

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
8
The software for this product is supplied on CDROM and included as part of
the Series 900MB Software Interface Package (Order Model 900C-SIP).
This software is used to configure Series 900MB modules and is installed
similar to other Windowsprograms. Any PC running Windowswith a
CDROM drive may be used. Simply insert the CDROM into your drive. Click
on the [START] button in the lower left hand corner of your Windows screen.
Then click the “Run…” icon and execute SETUP.EXE. This will execute the
Installshield Wizard for this program. Follow the on-screen instructions to
complete the installation.
In addition to configuring all features of the module, the Modbus
Configuration Software includes additional features as follows:
•Allows a configuration to be uploaded or downloaded to/from the
module via the RS485 interface.
•Polls the module & allows polling to be turned on or off.
•Monitors the input frequency or event count.
•Monitors/controls the discrete output signal states.
•Reads the contents of the Module Status Register.
•Provides controls to reset one or both event counters.
•Provides controls to reset a module.
•Provides controls to separately recalibrate each input frequency
range (high endpoint).
•Allows optional user documentation fields to be saved to a module
file on the PC.
•Allows a module’s complete configuration to be printed in an easy to
read, one or two page format, including user documentation.
The following section will walk you through the software. You should have a
module connected in order to access all pages of this software. Use of the
Acromag software is the easiest method of setting up your module. For
additional details on configuration of your module, please refer to the
Technical Reference section at the back of this manual.
For detailed information on Modbus, please refer to our technical reference
“Introduction To Modbus” (8500-648), available as a download from our
website at www.acromag.com. This guide thoroughly explains Modbus as it
relates to the Acromag 900MB modules and is an important supplement to
this manual.
CONFIGURATION
SOFTWARE
Installation

BusWorks942MB Module User’s Manual Dual Frequency Input
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Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
9
Click on the Series 900MB program icon to boot the Configuration Program
and the screen above will be displayed.
Click on the “Settings-Serial Communications…” pull-down menu (or press
Ctrl-E) to set the COM port, baud rate, parity, and slave address that the
host computer will use to communicate with the module.
Set the host Communication Port the module is connected to (COM1-
COM4), or type in a COM port from COM1 to COM99.
Set the host Baud Rate for communication with the module.
Set the host Parity to Odd, Even, or No Parity error checking.
Set the Slave Address the host is to use to talk to the module.
Use File-New to create a new configuration file.
Use File-Open to open an existing configuration file.
Use File-Save to save the current configuration file to disk.
Use File-Save As to save the current configuration file to a new file name.
Use File-Print to get a printout of the currently loaded configuration file.
Use File-Print Preview to preview a printout of the current configuration.
Use File-Print Setup to select a printer and font style.
Use Module-Upload Configuration to upload the module’s current
configuration and calibration (recommended).
Use Module-Download Configuration to write the currently loaded
configuration to the module.
Use Help to obtain information about using this software or configuring
transmitters. Note that context sensitive help (?) is also available for help
on a specific field or topic. Simply click on the [?] button, then click on the
field or topic of interest to obtain help on that subject. You may also click the
right mouse button to copy or print the help screen while it is being
displayed.
Starting The Program
The host COM port setting is
indicated in the first box of the
lower right-hand corner.
MODULE is indicated in the
third box if a connected
module is detected by the
software. The fourth and fifth
boxes indicate NUM for Num
lock and CAP for Caps lock,
respectively.
↑
↑ You can check this box to
automatically change host
settings to match new module
settings following download.
Uploading first is
recommended as it will
automatically detect the
correct model connected and
load the property sheets for
that model.

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
10
This screen is displayed once you choose to create, open, or upload a file.
Optional documentation: Enter a “Tag:” (15 characters), “Comment:” (31
characters), “Configured By:” (15 characters), “Location:” (25 characters),
“ID Channel:” (15 characters). This info is not stored within the module.
Use the scroll bars of the following fields to make a selection. Your selection
will take effect following the next download.
Set “Slave Address” from 1 to 247.
Set “Baud Rate” (2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600,
76800, or 115200 bits per second).
Set “Parity” to Odd, Even, or No Parity error checking.
If you already checked the “Update Communications settings at download”
box of the Settings pull-down menu, the host software will change its own
settings to match the new module settings that take effect after download in
an effort to maintain communication with the module.
Some host software or signal converters may require a communications
turnaround delay to work properly. Set “Response Delay” from 0 to 65500
ticks (1 tick=1.085us) if required. This will add delay between message
receipt by the module and its response to the host. Since a fixed amount of
delay is already present, you will have to specify a comparable amount of
response delay to measure any affect.
You can enable the I/O Watchdog Timer by setting “Watchdog Timeout:”
from 1 to 65534 seconds (0 or 65535 will disable timer). A timeout will occur
if no I/O data transfer occurs within this time period. You may optionally click
the “Watchdog Reset” check box to also send the digital outputs to their
reset states upon watchdog timeout (Reset States are set separately via the
Configure Alarms screen).
Creating A
Configuration File
The model number is indicated
at the top of the screen along
with the current file name.
Note that address, baud rate,
& parity selections take effect
following a configuration
download, but do not alter the
settings used by the host
software which is configured
separately via the Settings
pull-down menu.

BusWorks942MB Module User’s Manual Dual Frequency Input
___________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
11
Click the Input Setup tab to display the screen shown above. Input Setup is
used to specify parameters for the frequency or event counter inputs
(parameters apply to both inputs together).
IMPORTANT: Count memory is volatile and totalized count values are not
retained following loss of power.
General Setup
Use the field scroll bars to select parameters as follows:
For “Range:”, pick 0-50KHz, 0-1KHz, 0-100Hz, or Event Counter.
For “Threshold/Hysteresis:”, pick Bipolar 0.0V (25mV), Bipolar 0.0V
(83mV), Unipolar 1.5V (25mV), or Unipolar 5.0V (83mV).
For “Input Resistor”, select an input pull-up to the internal +5V supply, an
input pull-down to RTN, or none to leave the input pull resistors
disconnected.
Frequency Setup
Use the “Gate Time:” scroll bar to select a time period from 0.1s to 1.0s in
0.1s increments. This is the fixed time over which a number of input cycles
is counted in order to calculate the period & frequency for the 0-50KHz range
only.
Enter an integer from 1-255 into the “Cycles:” field to set the number of
cycles to sample for the 0-1KHz and 0-100Hz ranges only. The total time to
acquire this many cycles is used to calculate the period and frequency for
the 0-100Hz and 0-1KHz ranges.
Enter a “Cutoff Freq:” into this field to set the minimum measurable
frequency for the 0-100Hz and 0-1KHz ranges only. Frequencies below
0.5Hz (default), or below the specified cutoff frequency, will read as 0Hz.
Specify a cutoff frequency to minimize the time to detect a loss of signal for a
large number of cycles at low frequencies.
Input Setup
Thresh/Hysteresis Selection:
Sine Waves (Zero Crossing):
Set Bipolar 0.0V (  25mV).
Square Waves (Logic Level):
Set Unipolar 1.5V (  25mV).

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
12
Event Setup (Event Counter Only)
In the “Debounce Time:” field, enter an increment multiple of 5ms from 0-
200 (Default=1). This is the amount of time the module will wait following an
event before it will allow another event to occur. Your maximum count rate
will be reduced with increased debounce time.
Use the “Trigger Edge:” scroll bar to select the rising (positive-going) edge,
or falling (negative-going) edge, of the input pulse that will trigger an event
count.
Use the “Termination Type:” scroll bar to select Auto-Reset, or Latch for
the event counter. Auto-Reset will turn the alarm output ON for 100-200ms
and reset the counter back to 0 when the limit value has been reached.
Latch will turn the output ON upon reaching the limit and stop counting
events, until the event counter is reset.
Use the “Acquire Count:” scroll bar to select No (default), or Yes.
Normally, the event counter uses a high limit and alarm output to indicate it
has reached a defined count limit and this keeps accurate count. Choosing
“Yes” will cause the sampling controller to also send the running count to the
main micro every 100ms for display purposes, rather than just relying on the
high limit to report where the count is. However, choosing “Yes” can cause
the sampling controller to miss events during the time it’s reporting the count
and this can decrease count accuracy. This field is set to “No” (off) by
default and its use must be carefully considered where exact counts are
required. Note that the totalized count value is volatile and will not be
retained following loss of power.
The next section covers alarm configuration.
Note that the corresponding
High limit must be separately
enabled to control the
associated digital output.
CAUTION: Selecting “Yes” to
periodically acquire the event
count may cause the event
counter (the sampling
controller) to miss events for
the time it takes to report its
count to the main processor.
You have the option of
reporting the running count,
but at the possible expense of
count accuracy. Keep this in
mind for critical counting
applications.

BusWorks942MB Module User’s Manual Dual Frequency Input
___________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
13
Limit Alarm (Each Input)
Hi/Lo Alm Output Enable: Click to check this box and enable the High
and/or Low Limit alarm output for each input.
High Limit/Event Counter Setpoint: Enter a high limit in Hertz (or events).
The corresponding alarm output will go to its alarm state for an increasing
input signal that equals or exceeds the high limit (if enabled).
Low Limit (Not For Event Counters): Enter a low limit in Hertz. The
corresponding alarm output will go to its alarm state for a decreasing input
frequency that equals or goes below the low limit (if enabled).
Deadband (Not For Event Counters): Deadband is applied to both limit
levels and determines the amount the input signal has to return into the
“normal” operating range before the corresponding solid-state alarm relay
will transfer out of the “alarm” state.
Alarm Mode (Each Input): Select Failsafe or Non-Failsafe alarm output
action. A failsafe alarm output will turn OFF in alarm (the same state as the
power-down state). A non-failsafe alarm output will turn ON in alarm. Alarm
outputs must be separately enabled.
Alarm control of an output will take precedence over direct control when the
High/Low Alarm Output Enable box is checked. Keep this in mind if you try
to control the state of an alarm output directly, as the module will seek to
maintain the correct output state each time it scans the input, relative to the
alarm condition and alarm mode. This does not apply for input signals within
the deadband region, where the output state can be controlled directly.
However, direct control of an alarm output is not recommended.
Alarm Configuration
Limit checking is always active
for this module. The default
limits are the input range
endpoints.
Limit alarm control of the
corresponding output takes
priority over direct control
when enabled.
Be sure to enable the High
Alarm Output for event
counters, especially with
Acquire Count set to “No”.
Deadband is normally used to
eliminate false trips or switch
“chatter” caused by
fluctuations of the input near
the limit.

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
14
There are three methods of detecting an alarm: the output status LED can
be used to indicate a transfer to the alarm state, a global limit exceeded flag
will be set in the Module Status Register, and a high and/or low limit flag will
be set in the Channel Status Register.
Watchdog Output Reset Value: This selection determines the state the
output will be automatically toggled to following a watchdog timeout. Select
“On” or “Off” as required. Watchdog timer control of the output will take
precedence over alarm & direct control.
After making your General and Alarm Configuration selections, you must
download the new settings as follows:
Select Module-Download
Configuration to write your configuration to the module.
Module
Upload Configuration
→Download Configuration
Note that you can select Module-Upload Configuration to retrieve the
module’s current alarm configuration/calibration, or to review and verify its
configuration. Configuration data is stored in non-volatile memory within the
module.
You can select File-Print-Preview to preview this document before printing.
If you wish to document your transmitter configuration, then select File-Print
to get a two page printout of all of your selected configuration parameters.
The currently loaded configuration file name is indicated at the top of the
screen to the right of the model number.
You should select File-Save As to save your configuration file to disk and
give it a new file name.
Use File-Save to save the current file without renaming it.
In the event that you lose a configuration file, you can always upload it from
the module via Module-Upload Configuration.
Now wasn’t that easy! That’s all there is to using the Configuration software
to configure your module. The module is now ready for installation in the
field.
The next section covers testing of your configuration. If you have made
changes to any of the module configuration screens, be sure to download
your changes to the module prior to invoking any of the active Test or Input
Calibration pages.
The Test Page of this software
program will also report the
alarm status for the module
and at an input channel.
Writing Your
Configuration
Printing Your
Configuration
Saving Your
Configuration

BusWorks942MB Module User’s Manual Dual Frequency Input
___________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
15
Click the “Test” tab to display a screen similar to the one above. This screen
allows you to actively interact with and poll the module, monitor the module
status flags and I/O values, reset the module, and control and monitor the
outputs.
The flashing green dot of “Polling Status” indicates the software is
communicating with the module and polling its I/O. Polling is automatic
when this screen is displayed and turns off if another screen is selected.
The LED’s of the graphic simulation will reflect actual module LED states.
For Event Counters, you can click the CH0, CH1, or BOTH Event Counter
Reset buttons to reset event counters.
You can reset the module by clicking the “Reset” button (same effect as
power-on reset).
For each input, the current selected input range, input value (“Value:”), and
input status is indicated. Output states are also indicated. You may turn
outputs On or Off by clicking the “Output On” and “Output Off” buttons
(assuming they are not already enabled as alarm outputs).
Clearing a watchdog timeout by initiating I/O with a module that has timed
out will not automatically return the digital outputs to their pre-timeout state.
It simply returns control of the output state to the alarms, or to the operator
via manual control. Watchdog timeout control of the output has the highest
priority (if enabled), followed by alarms (if enabled). Manual control of the
outputs has the lowest priority.
The next section covers calibration of your frequency inputs. Calibration has
already been done at the factory and adjustment is not generally required.
However, periodic re-calibration may be performed to correct for component
aging, or as part of your company’s maintenance requirements.
Testing Your Module
CAUTION: Always download
your changes to the module
before invoking the active Test
or Input Cal pages as selecting
this page may change some of
your software settings to
match those obtained from
polling the module.
Note that the count value is
volatile and will not be retained
following loss of power.
Note that a module will exit the
Default Mode following a reset.
Keep in mind that alarm
control of an output has priority
over direct control (if enabled)
and will seek to maintain the
correct output state relative to
the input level each time the
input is scanned.

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
16
Module Input Calibration (Frequency Inputs Only)
Calibration is simplified using the controls of this software. Simply connect
the high-endpoint frequency indicated, then click the “Calibrate” button.
For best results, you will need a precision signal generator capable of
producing the high calibration frequency indicated, and at least as accurate
as the module itself. If calibration is attempted with equipment of poor
accuracy, then recalibration may degrade performance, or possibly render a
channel inoperable.
Module Input Calibration
1. Click the Input Calibration tab to display the screen shown above.
Note that Module-Upload Configuration will recall the module’s current
calibration. After uploading, the current active calibration values are
indicated in the High Calibration Value field of each input. These
correspond to the selected input range’s upper endpoint signal.
2. Observe proper polarity and wire your frequency generator to the input
channel you wish to calibrate. Adjust this input frequency to the High
Calibration value indicated.
3. Note the measured frequency indicated in the Value field at the top of
the screen. If the indicated value does not precisely match the High
Calibration Value, then click the High “Calibrate” button to reset the
High Calibration endpoint. After a moment, the value indicated at the
top of the screen should closely match the High Calibration Value. If
not, carefully repeat this procedure.
4. Repeat steps 2-3 for the second input channel, as required.
INPUT CALIBRATION
CAUTION: Always download
your changes to the module
before invoking the active Test
or Input Cal pages as selecting
this page may change some of
your software settings to
match those obtained from
polling the module.
IMPORTANT: Calibration of
the input ranges has already
been done at the factory.
Recalibration is normally not
required, except as necessary
to correct for long term aging
effects.
We recommend a Gate Time
setting of 1 second with 0-
50KHz range and 8 Cycles
with the 0-1KHZ or 0-100Hz
ranges to improve
measurement accuracy.
Uploading first will help
prevent miscalibration if the
input range set at the module
is different than that selected
via this software.
You may wish to
independently verify this
frequency via a precision
frequency counter.

BusWorks942MB Module User’s Manual Dual Frequency Input
___________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
17
The module routinely performs internal diagnostics following power-up or
reset. During this period, the green “Run” LED will flash for a moment. If the
diagnostics complete OK, the “Run” LED will stop flashing after a few
seconds and remain ON. This indicates the unit is operating normally.
If your problem still exists after checking your wiring and reviewing the table
below, or if other evidence points to another problem with the unit, an
effective and convenient fault diagnosis method is to exchange the module
with a known good unit. Acromag’s Application Engineers can provide
further technical assistance if required. Complete repair services are also
available from Acromag.
SYMPTOM
POSSIBLE CAUSE
POSSIBLE FIX
Cannot
communicate.
Is power ON at the
module and/or
RS485 converter?
Check power. Is green RUN
LED ON?
Is baud rate correct?
Check baud rate settings at the
host, module, and/or any
RS485 signal converter or
repeater.
Is address correct?
Check address settings at the
host and at the module.
Is parity correct?
Check parity settings at the
host and at the module.
Additional response
or turnaround delay
time may required.
Some host systems
or signal converters
require additional
turnaround delay to
work properly.
Try increasing the Response
Delay Time at the module.
Setting is found by
experimentation and you must
specify a time that is greater
than the inherent time already
present to notice a difference.
Have you tried the
Default
Communication
Mode?
Press the DFT button until ST
LED begins to blink. In this
mode, the baud rate is 9600,
the address is 247, and no
parity is set.
Continuous flashing
green RUN LED.
Internal firmware
problem.
Return module to factory to
restore firmware.
Communication was
lost while in the
Default Mode.
Has module been
reset?
Module leaves the Default
Mode if reset and internal
baud, address, & parity
settings take effect. Press
DFT button until ST LED blinks
to re-enter Default Mode.
Input frequency is in
error or input is
inoperable.
Miscalibration
Use the Configuration Software
to recalibrate the input
channel. Check your signal
generator.
Missing pullup or
pulldown?
Review input resistor selection.
Wrong threshold?
Review selection of
polarity/threshold/hysteresis.
SYMPTOM
POSSIBLE CAUSE
POSSIBLE FIX
TROUBLE-SHOOTING
Diagnostics
Some network converters or
host/software systems cannot
accept an immediate response
from a slave device without
additional delay inserted
between message receipt and
module response.
Diagnostics

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
18
Input frequency
measurement
indication is much
lower than actual
or 0Hz.
Aliasing - Input signal
is too fast to be
sampled.
Limit maximum input
frequency below 110% of
nominal. The maximum
measurable frequency of
your unit is about 54.5KHz.
Missing pullup or
pulldown?
Review selection of input
resistor.
Wrong threshold?
Review selection of
polarity/threshold/hysteresis.
Event counter is
missing events.
Is Acquire Count
enabled?
Count accuracy can be
degraded if Acquire Count is
set to Yes, as the sampling
controller can miss events
during the time it takes to
report its running count.
Disable Acquire Count and
use the High Limit alarm to
report count.
Has power been
cycled?
Totalized count values are
volatile and are not retained
following loss of power.
Debounce Time is too
long.
Reduce Debounce Time.
Frequency of events is
too fast.
With debounce time set to 0,
the maximum count rate that
can be obtained is about
200 samples per second.
Reduce the frequency of
events.
Missing pullup or
pulldown?
Review selection of input
resistor.
Wrong threshold?
Review selection of
polarity/threshold/hysteresis.
Yellow ST status
LED remains ON.
Indicates Over-range
at an input.
Reduce input frequency.
Yellow ST status
LED blinks slowly.
Indicates module is in
Default Mode.
To exit Default Mode, You
can press the DFT button,
reset the module, or cycle
power off/on to the module.
Yellow ST status
LED blinks rapidly.
Indicates a watchdog
timeout has occurred.
I/O communication with the
module will clear a timeout.
Yellow ST LED
blinks in rapid
bursts.
Indicates both Default
Mode and watchdog
timeout.
See above.
Cannot get unit to
indicate Default
Mode or
Watchdog
Timeout.
Yellow ST LED is
always ON.
This occurs if input
frequency is over-range
(between 100 and 110% of
full-scale). Reduce input
frequency until ST LED
changes state.

BusWorks942MB Module User’s Manual Dual Frequency Input
___________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
19
TECHNICAL REFERENCE
•Easy Setup With WindowsConfiguration Software –You don’t
have to be a programmer to quickly setup and operate this module.
•RS485/Modbus Network Interface –Highly immune to noise and can
operate over long distances. Allows many modules to network together.
•High-Speed Data Rates –RS485 up to 115K baud.
•Nonvolatile Reprogrammable Memory –Allows the functionality of this
device to be reliably reprogrammed thousands of times.
•Fully Isolated –The inputs, outputs, network, and power are all isolated
from each other for safety and increased noise immunity.
•Wide-Band Frequency Inputs With Event Counter - Two channels of
frequency in 3 ranges from 0Hz to 50KHz, plus event counter.
•High Voltage Inputs –Signal amplitudes up to 140VAC, or 200V peak.
•Flexible Interface Supports Many Input Types –Programmable pull-
up and pull-down resistors provide support for a variety of input types.
•Supports Bipolar or Unipolar Input Signals –Variable input bias for
both zero crossing and non-zero crossing periodic signals. The voltage
threshold and relative hysteresis are also user-selectable.
•Plug-In Terminal Blocks & DIN-Rail Mount - Make mounting, removal,
and replacement easy.
•Event Counter Alarm Function –Counts pulses on the positive or
negative edge, upward, in the range 0-65535. Counter may latch at a
high limit and turn the high alarm output ON, or pulse the alarm output
and reset itself to 0 after reaching the high limit. Counter(s) may be
reset remotely.
•Input Filtering - Inputs include hysteresis, over-sampling (frequency
inputs), debounce (event counter), and deadband (alarms).
•Dual Discrete SSR or Alarm Outputs - High voltage/current solid-state
switches provide for direct or alarm control of external devices, with both
failsafe and non-failsafe modes.
•Self-Diagnostics & Built In Watchdog - For easy maintenance and
troubleshooting. Includes a hardware watchdog timer built into the
microcontroller that causes it to initiate a self reset if the controller ever
“locks up” or fails to return from an operation in a timely manner.
•Wide-Range DC-Power or 24VAC Power - Non polarized and diode-
coupled for use with redundant supplies, and/or battery back-up.
•I/O Watchdog Timer –For periods up to 65534 seconds (18.2 hours).
Timer will timeout if an I/O channel read or write operation does not
occur for the configured time period. Outputs may also be automatically
set to user-defined states following timeout.
•Hardened For Harsh Environments - For protection from RFI, EMI,
ESD, EFT, & surges. Has low radiated emissions per CE requirements.
•Wide Ambient Operation –Reliable over a wide temperature range.
•LED Indicators - A green LED indicates power. A yellow status LED
indicates over-range, default communication mode, and watchdog
timeout. Another yellow output LED indicates the On/Off output state.
•Push-Button Default Communication Mode –Can set the module to
a default set of communication parameters for baud rate, module
address, and parity if its internal settings are unknown.
•Alarm Function With Variable High and Low Limits Plus Deadband -
Includes optional failsafe or non-failsafe alarm outputs.
KEY FEATURES

BusWorks942MB Module User’s Manual Dual Frequency Input
__________________________________________________________________
______________________________________________________________________________________
Acromag, Inc. Tel:[phone] Fax:[phone] Email:[e-mail] http://www.acromag.com
20
These transmitters use a comparator and logic gate to convert the input
signal into a digital pulse stream. The comparator provides the threshold
and hysteresis, while the logic gate will “square” the wave-shape. Separate
microcontrollers sample the input pulse streams and track the number of
internal clock cycles to determine the period of the input signal and its
frequency. Two methods of determining frequency are used according to
the input range.
For the 0-50KHz range, the microcontroller counts the number of input
cycles over a gated time period from 0.1 to 1.0s (Gate Time) and calculates
the relative period and frequency. Thus, the longest Gate Time is 1 second
for this range making 1Hz the slowest possible frequency that can be
measured. For this range, input frequencies below 1Hz will read as 0Hz.
For the 0-100Hz and 0-1KHz ranges, the microcontroller measures the
period of a signal by counting a specified number of cycles while using the
internal clock to track the total time. The total time divided by the number of
cycles determines the period. The lowest measurable frequency for these
ranges is 0.5Hz, but with a slow input frequency and a high number of
cycles, the time to detect a loss of signal may be high. In this case, a
specified cutoff frequency is used and any frequency below the cutoff will
read as 0Hz.
The microcontroller will compute the input frequency and complete the
transfer equation according to the input type and its embedded function.
The microcontroller also compares the signal value to the limit value for the
alarm function and completes all necessary alarm functionality according to
its embedded program. I/O lines of the microcontroller will switch the solid-
state relays ON/OFF, as required. The UART of the microcontroller
sends/receives its I/O signals to the network via an optically isolated RS485
transceiver. Embedded configuration and calibration parameters are stored
in non-volatile memory integrated within the controller. New module
functionality can be downloaded from a host computer running the Modbus
Configuration Software, or other compatible Modbus software via the
network interface. Refer to the simplified schematic that follows to gain a
better understanding of the circuit.
RTN
RTN
UNIP
DIV
PDN
PUP
PDN
+5V
PUP
BIPO
D
DIV
+5V
D
FRQ0
CH1
1.5V REF
+5V
+5V
+5V
RS485
TRANSCEIVER
OUT0(+)
RTN (-)
RS485
COM
PWR
10-36V DC
24VAC
OUTPUT/
ALARM
STATUS
FRQ1
DEFMODE
SWITCH
CH0 PUSH FOR DEFAULT
MODE -STATUS LED
FLASHES
+5V
3
+5V
+5V
REG
+5V
REG
SWITCHINGPOWER
OUT1(+)
ISOLATED POWER
POWER -
ISOLATED
FLYBACK
STATUS LED
MAIN MICRO
CONTROLLER
ISOLATED DIGITALOUTPUTS (SOLID-STATE RELAYS)
OPTICAL
ISOLATION
ISOLATED RS485PORT
CH1MICRO
CONTROLLER
PWR LED
MODEL 942MB-0900
SIMPLIFIED SCHEMATIC
CH0MICRO
CONTROLLER
ISOLATED INPUT INPUTPOWER
HOW IT WORKS