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900MB

SeriesFrequency/Counter Module

Modbus/RS-485

Inputs (2)TwoFrequencyorPulse
Waveform
InputsTwoDiscreteOutputs
orLimit Alarms

Outputs (2)BusWorks® Modbus I/O

Isolation

942MB
Frequency/
Pulse Counter
Modules
Periodic or Pulse
Waveform Input
Limit Alarms or
Discrete Outputs
Model
942MB: 2 input channels
Input
Two input channels:
0 to 50KHz in three selectable ranges
Amplitudes up to 140V AC or 200V peak
Pulse counter range of 0 to 65535
OutputTwo output channels:
Solid-state relays (1A DC loads)
0 to 48V DC
Network Communication
Modbus-RTU high-speed RS-485
Power Requirement
10 to 36V DC,24V AC
Approvals
CE marked. UL, cUL listed
Class I; Division 2; Groups A, B, C, D.

RS-485

Modbus10-36V DC
or 24V ACPower■ Description■ Special Features

This signal conditioner is a two-channel analog
input module with discrete outputs and Modbus
communication. It conditions periodic or pulse
waveform inputs and provides solid-state relays
for limit alarms or ON/OFF control.

■Standard Modbus RTU protocol with high-speed
RS-485 communication (up to 115K bps)■

Separate microcontrollers on each channel for
pulse counting and period measurement■

Solid-state relay outputs enable local limit
alarms or host-controlled on/off switching■

Bipolar and unipolar input signal support■

Programmable pulse counter functions■

Input filtering functions include hysteresis,averaging, debounce, relay time delay, andalarm deadband controls■

4-way isolation (input, output, power, network)■

Watchdog timers provide a failsafe output■

Self-diagnostics monitor microcontroller activity
to detect operational failures (lock-up) and
execute a reset to restore communication

Versatile inputs accommodate many applications
using TTL, magnetic pickups, proximity sensors,
or a variety of switches (high/low-side transistor,dry contact, open drain, open collector). Bipolar
and unipolar waveforms are supported with aselectable input bias that accepts both zero andnon-zero crossing signals. Voltage threshold andrelative hysteresis are also user selectable.
Inputs may also function as event counters withseparate microcontrollers for each channel. The
module counts pulses on the positive or negativeedge. It can wrap around to zero for continuous
counting, latch at a programmed count value(setpoint), or automatically reset itself to zeroafter reaching a setpoint value. Software controls
enable remote resets. A variety of filters help
remove noise, jitter, and other mechanical effects
to prevent false counts.
The discrete outputs can operate as independent
alarms or provide on/off control regulated by thehost system. As limit alarms, each output can be
set for high and/or low setpoints exclusively tied
to an analog input. These low cost modules are
ideal for standalone alarms as well as for local
backup of the primary control system.

Optional terminal blocks: barrier strip (left) andspring clamp (right). Cage clamp terminal is standard.

Tel: 248-295-0880 e-mail: sales@acromag.com www.acromag.com
8401-003

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Modbus■ Performance■ Frequency/Counter Input

Input Ranges
Input type user-configured. Applies to both channels.
Input Range
Accuracy Accuracy over Temp.
0 to 100Hz±0.04Hz ±0.06Hz
0 to 1000Hz±0.4Hz±0.6Hz0 to 50,000Hz±10Hz±15Hz
0 to 65,535 pulses ±1 pulse ±1 pulse

Input Filter Bandwidth

LED Indicators-3dB at 35kHz, typical.

LEDs indicate power, status, and discrete level/alarm.

Input Pullup/Pulldown■ Power and Isolation

Software selectable 2.7K ohm input pullup to +5V anda 1K ohm input pulldown to return. The resistors may
also be left floating (none).

Input Debounce

Amplitude: 0 to 3V minimum range,
0 to 200V peak maximum range.
Threshold: Configurable for 1.5V or 5V, typical.
Hysteresis: Configurable for ±25mV (at 1.5V threshold), or ±83mV (at 5.0V threshold), typical.

Output Type
Solid-State Relay (SSR), one Form A (SPST-NO) switch
per input channel. Outputs share a common return
connection at the RTN terminals for low-side switching

Output Voltage Range

0 to 100Hz input range: 0.01Hz
0 to 1000Hz input range: 0.1Hz
0 to 50,000Hz input range: 1Hz
Pulse counter: 1 pulse

0.4 ohms maximum.

Output Response Time
4.1ms typical, from receipt of command to gate
transition of the output MOSFET.

Operation

Supported Modbus Commands
The command/response protocol for communicatingwith this module adheres to the Modbus/RTU standard
for the following Modbus Functions.
Read Holding Registers
Read CoilRead Input Registers
Reset Slave
Preset Single Register
Report Slave ID
Force Multiple Coils
Force Single Coil
Preset Multiple Registers

10µS (frequency input); 5mS (pulse input).

Counting Rate
100Hz maximum counting rate
(5mS ON and 5mS OFF for 10mS period or 100Hz).

Input Impedance
35K ohms, typical.

DIGITAL OUTPUT CONNECTIONS
TB4

TB1

FRQ0

V+V+PWR

orDV+B
A+DIGITAL OUTPUTUP TO
48V DCNETWORKCOMMUNICATION

TB3

FRQ0

TTLCOMCOMDRTNDRY CONTACT

OUT0

TB3+FRQ0
RTN

RTN

TB4

HIGH-SIDE SWITCH(Open Collector/Drain)OUT1

MECHANICALRELAY INTERFACE

36 35 34 33 32 31

MAGNETIC INPUT

RTN

RS485

RTN

RTN

TB1

FRQ1

FRQ0

orRTN

-NC
FRQ1

DIGITAL OUTPUTSANALOGINPUT+FRQ0
RTN

FREQ. INPUT 0, 1

TB1

11 12 13 14 15 16

LOW-SIDE SWITCH(Open Collector/Drain)

FREQUENCY INPUT

NC

46 45 44 43 42 41

ANALOG INPUTCONNECTIONS-900C-SIP
Configuration Software Interface Package(includes software CD-ROM for Windows,RS-232/485 converter, and RS-485/three-wire cable)
4001-095
USB-to-RS232 adapter
TBK-B02
Optional terminal block kit, barrier strip style, 4 pcs.
TBK-S02
Optional terminal block kit, spring clamp style, 4 pcs.
PS5R-VB24
Power supply (24V DC, 2.1A)

Output ON Resistance■ Communication

Minimum Input Pulse WidthMAGNETICPICKUP

942MB-0900
Frequency/counter input module

Accessories

0 to 48V DC, 1A DC.

Digital outputs are set to their OFF state following asoftware or power-on reset. Outputs can be set touser-defined states following a watchdog timeout.

Resolution■ Ordering
Information

AC/DC
POWER
10 TO 36V DC
OR 24V AC
NON-POLARIZED

OUT
RTN

TB4

RTN

RTN
OUT 3

OUT
FRQ0
RTN

FRQ0
RTN

OUT 2
DIGITAL OUTSHARES
RETURN

RTN
OUT 1
OUT 0

Tel: 248-295-0880 e-mail: sales@acromag.com www.acromag.com
8401-003

BusWorks® Modbus I/O

Amplitude (0-20KHz): ±50mV minimum (with ±25mVhysteresis), or ±150mV minimum (with ±83mV hysteresis), to ±200V peak maximum.
Amplitude (Above 20KHz): ±100mV minimum (with±25mV hysteresis), or ±200mV minimum (with ±83mVhysteresis), to ±200V peak maximum.
Threshold: 0mV nominal, 0.01V typical with ±25mV
hysteresis; 0.03V typical with ±83mV hysteresis.
Hysteresis: Configurable for ±25mV or ±83mV, typical.

10 to 36V DC.
22 to 26V AC.
1500V AC for 60 seconds or 250V AC continuous.
4-way isolation between input, network, power anddiscrete I/O circuits. Inputs are isolated channel-tochannel for common mode voltage to ±5V DC.

Noise Rejection■ Discrete Output

Bipolar (Zero-Crossing) Input Configuration

Power RequirementsIsolation

0 to 1.375 seconds, configurable in 5mS increments.
Common mode: 80dB @ 60Hz, typical with 100 ohm
input unbalance.

Unipolar Input Configuration

FREQUENCY
GENERATOR

I/O

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900MB

Series

900MB Series Technical Diagrams
TB4

TB3

Acromag

DFTB
A

D

D

TB3

TB1

2.34
(59.4)

BusWorks® Modbus I/O

PWR

TB2

2 3

CLRS4853.75(95.3)

0 1

36 35 34 33 32 31

TB4

STCOMCOM

46 45 44 43 42 41

RUN

4.68(118.9)"T" Rail Din Mounting
Din EN 50022, 35mm

11 12 13 14 15 1621 22 23 24 25 26

TB2TB13.90(99.1)

1.05(26.7)
NOTE: ALL DIMENSION ARE IN INCHES (MILLIMETERS)

4.35(110.5)

PERSONAL COMPUTER
W/ WINDOWS 95/98 OR NT
RS-232 SERIAL
PORT CONNECTOR
AT BACK OF PC

PC RUNNING
ACROMAGMODBUS CONFIG
SOFTWARE

INSTALL MODBUSCONFIGURATIONSOFTWARE

RS-232 TO RS-485 CONVERTERMODEL 5034-214

CONNECT THE RS-232
SIDE OF CONVERTERTO THE PC

CAUTION: DO NOT CONNECT THE
CABLE DIRECTLY TO THE PC WITHOUTTHE CONVERTER, OR DAMAGE TO
THE MODULE MAY RESULT.

CABLE 5034-202

CONNECT THE RS-485
SIDE OF CONVERTERTO THE CABLE

900C-SIP COMMUNICATION CONNECTIONSCBACONNECT WIRES AS SHOWNCOM DTB4TB4Acromag
RUNRED

RS-485DBBLACKDCGREENCOM

REFER TO THE USER'S MANUALTHAT CAME WITH YOUR MODULETO COMPLETE THE MODULE'S
POWER AND I/O CONNECTIONS

TB2

TB1COLORA

PWR

ANY 900MB MODULE

TB1R

A

STATUS LED FLASHES IN
DEFAULT MODE.

B

RS485

DDEFAULT MODE SWITCH PUSH FOR DEFAULT MODE.

DTB33WIRE

36 35 34 33 32 31
COM

246 45 44 43 42 41

TB3COM

1RUN/PWR LED (GREEN)
STATUS LED (YELLOW)TB4STDFT0D

11 12 13 14 15 16

21 22 23 24 25 26

TB1

TB2

Tel: 248-295-0880 e-mail: sales@acromag.com www.acromag.com
8401-003

(This page intentionally left blank.)

Modbus

I/O■ Performance■ General■ Discrete Inputs(901 & 903 models only)
Input Type

5.6K ohm pull-up resistor SIPs are installed in sockets
at each port (four-channels per port).

I/O Pull-ups and Socket

12 active-low, buffered inputs, with a common connection. Inputs include transient suppression devices
and series connected 100K ohm resistors, plus diodeover-voltage clamps to the internal +5V supply.

Excitation (per port)

External excitation voltage for each four-channel port
is limited to 35V or less.

Supported Modbus Commands

0 to 35V DC, maximum.

Input Current

293µA, typical at 35V DC.

Input Signal Threshold

TTL compatible with 100mV of hysteresis, typical.
Low-to-High threshold is 1.7VDC, High-to-Low is
1.6VDC, typical. Limited to TTL levels of 0.8VDC(max. LOW level) and 2.0VDC (min. HIGH level).

Input Resistance

100K ohms, typical.

LED Indicators

Input Hysteresis

LEDs indicate power, status, and discrete level.

100mV DC, typical.

Power Requirements
10 to 36V DC,
22 to 26V AC.

■ Discrete Outputs(902 & 903 models only)
Output Type

12 independent, open-drain, DMOS MOSFET switcheswith a common source connection that operate as
low-side switches.

Output Voltage Range

0 to 35V DC max. (0 to 500mA/channel continuous).
External voltage source required.

Output ON Resistance
0.28 ohms maximum.

Models901MB-0900
Discrete input module
902MB-0900
Discrete output module
903MB-0900
Discrete input/output module

Accessories

900C-SIP
Configuration Software Interface Package(includes software CD-ROM for Windows,
RS-232/485 converter, and RS-485/three-wire cable)
4001-095
USB-to-RS232 adapter
TBK-B02
Optional terminal block kit, barrier strip style, 4 pcs.
TBK-S02
Optional terminal block kit, spring clamp style, 4 pcs.
PS5R-VB24
Power supply (24V DC, 2.1A)

Supply Current
Supply10V DC
24V DC
24V AC

Current Draw
130mA maximum
54mA maximum
95mA maximum

Isolation

1500V AC for 60 seconds or 250V AC continuous.
3-way isolation between I/O, network, and powercircuits.

Output Response Time

Optional terminal blocks: barrier strip (left) andspring clamp (right). Cage clamp terminal is standard.

Force Single Coil: Output updates within 250µs ofreceipt of a command.
Force Multiple Coils: First coil updates in 250µs,
followed successively by additional coils every 180µs.
DIGITAL INPUT CONNECTIONS (ACTIVE LOW)

DIGITAL OUTPUT CONNECTIONS+ 12-24V DC,

CH 3
RTN

CH 0
CH 1
CH 2
CH 3

INTERNAL INPUT
PULL-UPS ARE PRESENT

CH 7
RTN

CH 8
EXC3COMCOM
DDBA100KTB3TO OTHER 3
CHAN OF PORTDIGITAL
I/O

5-35V

ON

OFF

NETWORKCOMMUNICATION

RTN

AC/DC
POWER
10 TO 36V DC
OR 24V AC
NON-POLARIZED

TB1
EXC1OUTCH 0
DIGITAL I/O
SHARES
RETURNRTN

CH 1CH 2CH 3
RTN

RTN

Tel: 248-295-0880 e-mail: sales@acromag.com www.acromag.com

8401-003

V
I/O

902MB/903MB

TB3

EXC1CH 6

CH 936 35 34 33 32 31

TB2

TB1CH 5PWR

RTN

CH 4CH10

TB4

RS485

DIGITAL
I/O

EXC2

DIGITAL IN or OUT

21 22 23 24 25 26

INP
SPST
RELAY

RTN
CH11903MB shown.
901MB & 902MB
are similar.

TB2TYPICAL

RTN

CH 2

TB1

RTN

CH 1

TB4

EXC

DIGITAL
I/O

CH 046 45 44 43 42 41

INP

11 12 13 14 15 16

RTN

EXC1

DIGITAL IN or OUT

TB1
DIGITAL IN or OUT

EXC
INP

DIGITAL I/O
SHARES
RETURNLOAD+5V+5V

INP

EXC

903MB

5V TTL LOGIC - INPUT CAN BE PULLEDUP INTERNALLY OR EXTERNALLY

BusWorks® Modbus I/O

The command/response protocol for communicatingwith this module adheres to the Modbus/RTU standard
for the following Modbus Functions.
Read Coil (Output) Status
Read Input Status
Read Holding Registers
Force Single Coil (Output)
Preset Single Register
Reset Slave
Force Multiple Coils (Outputs)
Preset Multiple Registers
Report Slave ID

Input Signal Voltage Range■ OrderingInformation

Accessories
Model 4001-095 USB-to-Serial Adapter
PERSONAL COMPUTERRUNNING WINDOWS
98/ME/2000/XP

HOSTUSBTO HOST USB PORT

USB MALE

HOST PC RUNNING
ACROMAGCONFIGURATIONSOFTWARE

4001095
USB SERIAL CONVERTERLEDRS232
DB9P

6 FEET OF CABLE

Simplifies configuration of Acromag I/O Modules ◆ Enables configuration via USB port

Description

Performance Specifications

Ordering Information

This device is a USB-to-serial adapter that you
can use to communicate with many Acromag I/O
products for setup and re-configuration for yourapplication.

USB Specification
Version 1.1
Data rate
Up to 115.2Kbps
Environmental Standards
RoHS-compliant
Basic Power Consumption
150mA
PC Requirements
Windows® 7 and newer.

NOTE: For more information visit www.acromag.com.

Key Features & Benefits■

Connects to I/O modules via USB(other adapters may be necessary)■

Complete RS232 control signals■

Conforms to USB Specification, Version 1.1■

USB-powered■

Cable length, 6 ft., UL approved

Adapters
4001-095
USB to serial adapter. Includes driver CD and manual.
5030-913
Serial port adapter. DB9S connector to RJ11 jack.
5034-202
RS-485 to 3-wire cable converter and cable, DB-9M to3 x 12AWG RS-485 cable, 8 ft.
5032-787
RS-232 to 151T transmitter configuration device
converter and cable, 6 ft.
5034-214
Non-isolated RS-232 to RS-485 Serial Port Converter,
DB-9F to DB-9F.

CablesIntelliPack 800x Series
Adapter and Cable
9-PIN CONNECTOR (DB9S)

INTELLIPACKSERIAL ADAPTER

RJ11 JACK(6 CONDUCTOR)

5030-902
Cable. 6 feet long with RJ11 plug at each end.

RJ11 PLUG(6 CONDUCTOR)MODEL 5030-902(6 feet long)

MODEL 5030-913

900MB Modbus Series
Adapter and Cable
RS232 TO RS485 SERIALCONVERTER(MODEL 5034-214)

CABLE 5034-202

RS-485

RS-2325034-202

C

DB9 FEMALE

DB9 FEMALE

B

A

DB9 MALECOM D D

Tel: 248-295-0880 ■ sales@acromag.com ■ www.acromag.com ■ 30765 S Wixom Rd, Wixom, MI 48393 USA
Bulletin #8400-572B

All trademarks are property of their respective owners. Copyright © Acromag, Inc. 2019. Data subject to change without notice. Printed in USA 5/2019.