917MB, 918MB: DC Current/Voltage Modbus-RTU Output Modules with Discrete Outputs

These modules drive four analog output channels and also feature four discrete outputs for on/off control. Isolation separates the output, power, and network circuits. Network communication adheres to the industry-standard RS-485 Modbus RTU protocol. AC and DC power sources are supported with non-polarized, diode-coupled terminals.

The analog outputs generate a signal based on communication from the host. They accommodate wide DC voltage or current ranges.

Discrete outputs provide simple on/off switching capability for external devices.

Combining analog outputs, on/off controllers, 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 make it reliable for both control room and distributed field I/O use in a broad range of temperature control applications. Custom module configurations are also possible (consult factory for details).

DC Current or DC Voltage Outputs
Discrete Outputs

Models:
917MB: 4 current output channels
918MB: 4 voltage output channels
Analog Output:
917MB: 0 to 20mA, 4 to 20mA, 0 to 1mA DC
918MB: 0 to 10V, 0 to 5V, 0 to 1V DC
Discrete Output:
Four output channels:
Open-drain MOSFETs (1A DC loads)
0 to 35V DC
Network Communication: Modbus-RTU high-speed RS-485
Power Requirement: 12 to 36V DC (917MB), 10 to 36V DC (918MB), 24V AC
Approvals:
CE marked. UL, cUL listed
Class I; Division 2; Groups A, B, C, D

Performance Specifications

General Analog Output

Resolution: See current/voltage output specifications for more information.
Ambient Temperature Effect: Better than ±0.001% of output span per °C, or ±1.0uV/°C, whichever is greater.
Ambient Temperature:
Operation (917MB): -25°C to 60°C* (-13°F to 140°F*)
Operation (918MB): -25°C to 70°C (-13°F to 158°F)
Storage: -40°C to +85°C (-40°F to +185°F)
* Limit 917MB maximum ambient to 50°C (122°F) when using supply voltages less than 15V DC

Current Output (917MB)

DC Current Output Ranges: Range user-configured. Range selected applies to all channels.
Output Range     Resolution      Accuracy (% span)
0 to 1mA                0.554% ±2.0%           (±0.002mA)
0 to 20mA             0.028% ±0.1%            (±0.02mA)
4 to 20mA             0.035% ±0.1%            (±0.02mA)

Maximum Output Current: 22.5mA DC typical
Integral Non-Linearity: ±0.1% of span or ±2 LSB typical, whichever is larger, for spans equal to or greater than 16mA.
Output Compliance: 12V minimum, 12.7V typical
Output Load Resistance Range: 0 to 630 ohms typical
Response Time: 11ms typical into 500 ohms, for measurement to reach 98% of the final value in response to a step command. Actual response time will vary with load.

Voltage Output (918MB)

DC Voltage Output Ranges: Range user-configured. Selection applies to all channels.
Output Range      Resolution      Accuracy (% span)
0 to 1V                     0.274% ±0.6%             (±6mV)
0 to 5V                    0.055% ±0.1%              (±5mV)
0 to 10V                  0.027% ±0.1%             (±10mV)

Maximum Output Voltage: 11.255V DC typical
Integral Non-Linearity: ±0.1% of span or ±2 LSB typical, whichever is larger, for spans equal to or greater than 5V
Output Current: 0 to 10mA DC maximum
Output Impedance: 1 ohm
Output Short Circuit Protection: Included
Response Time: 110μs rise time typical, 150μs fall time typical, unloaded, for output to reach 98% of the final value in response to a step command. Time varies with load.

Discrete Output

Output Type: Four independent open drain MOSFET switches with a common return that operate as low-side switches.
Output Voltage Range:
0 to 35V DC (up to 1A/channel continuous)
External voltage source required
Output ON Resistance: 0.15 ohms maximum
Operation: Digital outputs are set to their OFF state following a software or power-on reset. Outputs may be set to user-defined states following a watchdog timeout. Watchdog timeout output control takes precedence over limit alarm control. Alarm control takes precedence over host control.
Output Response Time: 4.1ms typical, from receipt of command to gate transition of the output MOSFET

Communication

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 Report Slave ID
• Read Holding Registers Reset Slave
• Read Input Registers
• Force Single Coil (Output)
• Preset Single Register
• Force Multiple Coils (Output)
• Preset Multiple Registers

LED Indicators: LEDs indicate power, status, and discrete level/alarm

Power and Isolation

Power Requirements:
10 to 36V DC (918MB), 12 to 36V DC (917MB)
22 to 26V AC

Supply Current:
Supply    Current Draw (917)           Current Draw (918)
10V DC       Not Recommended              100mA maximum
12V DC        275mA maximum                   85mA maximum
24V DC        120mA maximum                   45mA maximum
24V AC         210mA rms maximum         85mA rms maximum

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