ST-MIX16880-D Usage Tips

Note: This combination I/O module is compatible with IPm stations and ST-GT-1210 / ET-GT-ST-3 controllers only. It is not compatible with legacy SIXNET stations such as SixTRAK gateways, VersaTRAK RTUs and the ET-GT-ST-1 / ET-GT-ST-2 I/O concentrators. Version 1.7 or new controller / IPm firmware is required to support this new I/O module. This firmware is available for free download from www.sixnetio.com.

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 cannot be reset under software control. Typically, retention of the values and resetting the counts is accomplished in software at the host computer that polls these inputs.

High Speed Counter

The first channel (and only the first channel) may be configured as a high speed counter 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.

Watchdog Output

The first discrete output in this module can be configured to be a watchdog output. This system performance monitor will be ON if:

• The output module is functioning normally

• The gateway is functioning normally

• ST-Bus communications are occurring normally

To configure a watchdog output, open the configuration window for the module and select the "watchdog output" feature. When the watchdog feature is enabled, the corresponding discrete output signal is ignored.

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 and Indication

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.

This module also has a status LED for each analog input. A Status LED will turn OFF if the corresponding 4-20 mA signal malfunctions or drops below approximately 3 mA.

Sourcing/Sinking Discrete Input Wiring

The discrete inputs in the ST-MIX16880-D may be configured as sourcing inputs (ON when positive voltage is applied) or sinking inputs (switch closures to ground). There is a Sink/Source jumper setting inside the base that is easily accessed by unplugging the logic module and opening the hinged door. The default factory setting is: "Sourcing (jumper to -)", which is appropriate for most situations in which a positive voltage is applied to an input to indicate an "ON" condition. Select "Sinking (jumper to +)" for "ON" inputs corresponding to ground closures that require a positive reference as an opposing return connection. It is also necessary to make a similar selection in the Discrete Options window in the I/O tool Kit software. The ST-MIX16880 firmware performs a consistency check to verify that the hardware and software selections match.

The inputs may also be modified to transition at a threshold voltage lower than the factory setting. This is accomplished by soldering a resistor into the base at the indicated location, according to the following chart. Please note that this resistor is only creating a reference voltage and therefore only needs to be rated for 1/8 Watt or less: