RM-RTU-8440-F Usage Tips

This module is an ideal solution for small I/O locations with just a few I/O points which may be a combination of discrete (switch closure) inputs, discrete outputs and 4-20 mA process signals and pulse accumulator channels.

Slow / Fast Response – Discrete Inputs

Select fast response for minimal input filtering to respond to DC input changes in 5 mS. Slow response looks for stable inputs for approximately 25 mS to filter contact bounce (important when counting mechanical switch closures) in noisy environments.

Pulse, Rate and Runtime Counters

Enable pulse counters for the first eight discrete inputs to increment an analog input register (SIXNET address AX8 - AX15 or Modbus address 30009 - 30016) each time an OFF to ON transition occurs on the corresponding discrete input (X0 – X7 or Modbus address 10001 - 10008). Other configuration choices include rate counters (report the number of pulses received in a selectable time period from one second to one minute), and also Run Time counters (report the number of seconds or minutes that the corresponding input is ON).

These counters report unsigned 16 bit values (0 - 65535) and are volatile (forget their counts if power is lost). These counters can be reset by toggling the counter reset bits Y8 – Y15. Typically, retention of the values and resetting the counts is accomplished in software at the host computer that polls these inputs.

Two High Speed Counters

The first two channels may be configured as a high speed counters to record pulses as fast as 10 KHz. In this high speed mode, the input filtering is not active, and even short input spikes will most likely be counted.

Self-resetting 4-20 mA Input Protection

Each 4-20 mA input channel has a 100 ohm, high precision (0.1 percent) shunt across its input to develop a 2 volt signal when a full scale 20 mA input is applied. Each shunt is located in the module’s base, giving you the advantage of maintaining a continuous circuit even if the logic module is removed from the base. If excessive voltage is applied to an input, a self-resetting fuse will open to help prevent the shunt from overheating.

Open Loop Detection

This module can detect and report an open instrumentation loop on its input. By allowing the module to report a negative value if the current falls below 4 mA, low limit logic in your DCS, PLC, RTU or computer can signal the loss of current. To enable this feature, select the "Go Negative Below 4 mA" setting for each individual channel.

Initializing Communications (Getting Control of the Serial Port)

The default factory setting for communications is 9600 baud, 8 data bits, no parity, one stop bit, SIXNET Universal protocol.

Situations may arise in which the module is configured to communicate in a manner that is not compatible (or known) to the I/O Tool Kit software. It may be for example, that the module is configured at a baud rate incompatible with the computer's serial driver, or it may be configured for Modbus. A feature is provided to enable you to regain control of the port for maintenance purposes.

First select the module you wish to address and then on the Operations --> Advanced Operations menu, select "Reset System Com Port". When you cycle the power on the module, the I/O Tool Kit software will trap the module as it initializes and reset the communications to the default factory settings. You may now perform the desired maintenance functions. Be sure to set the communications back to the necessary settings for system operation using a load command.

This feature will function over either RS485 or RS232 communications. Be sure to set the jumper in the module's base appropriately. Please note that this module may not be connected to an active (in use) RS485 network while the RS232 port is in use.