901MB, 902MB, 903MB: Multi-Channel Modbus-RTU Discrete I/O Modules

These modules provide twelve discrete input and/or output channels. Isolation separates the I/O, power, and network circuits. Network communication adheres to the industry-standard RS-485 Modbus-RTU protocol. Both AC and DC power sources are supported with wide range, non-polarized, diode-coupled terminals.

The open-drain outputs are intended for current-sinking or low-side switching applications. The buffered inputs are active-low. These models are the complement of the 904, 905, and 906 units which have open-source, high-side output switches and active-high inputs. Socketed pull-up resistors are easily removed or exchanged to satisfy your application requirements.

The 903MB model has twelve input/output points that may be used as inputs or outputs on a bit-by-bit basis. Outputs may be read back to verify output settings.

Combining flexible I/O types, wide I/O ranges, and a network interface in a single package, makes this instrument extremely powerful. Multi-channel design adds cost-efficiency and allows high-density mounting. Plus, safe, rugged construction makes these modules reliable for use in both control room and distributed field I/O applications. Custom module configurations are also possible (consult factory for details).

Active-Low Inputs Sinking Outputs (Low-Side Switching)

Models:
901MB: 12 input channels
902MB: 12 output channels
903MB: 12 input/output channels
Input:
Twelve input channels (901, 903 models only)
0 to 35V DC
Output:
Twelve output channels (902, 903 models only)
O to 35V 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

Performance Specifications

Discrete Inputs (901 & 903 models only)

Input Type:
12 active-low, buffered inputs, with a common connection.
Inputs include transient suppression devices and series connected 100K ohm resistors, plus diode over-voltage clamps to the internal +5V supply.
Input Signal Voltage Range: 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
Input Hysteresis: 100mV DC, typical

Discrete Outputs (902 & 903 models only)

Output Type: 12 independent, open-drain, DMOS MOSFET switches with 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
Output Response Time:
Force Single Coil: Output updates within 250μs of receipt of a command.
Force Multiple Coils: First coil updates in 250μs, followed successively by additional coils every 180μs

General

I/O Pull-ups and Socket: 5.6K ohm pull-up resistor SIPs are installed in sockets at each port (four-channels per port).
Excitation (per port): External excitation voltage for each four-channel port is limited to 35V or less.
Supported Modbus Commands: The command/response protocol for communicating with 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

LED Indicators: LEDs indicate power, status, and discrete level.
Power Requirements:
10 to 36V DC
22 to 26V AC

Supply Current:
Supply         Current Draw
10V DC    130mA maximum
24V DC      54mA maximum
24V AC      95mA maximum

Isolation:
1500V AC for 60 seconds or 250V AC continuous
3-way isolation between I/O, network, and power circuits