DigiRail OEE and Digirail IoT IO Modules

What Is the Difference Between DigiRail OEE and DigiRail IoT Remote I/O Module Models?

NOVUS DigiRail OEE and DigiRail IoT models are very similar in terms of their I/O structure and general communication features. The main difference between the two models is the available operating modes of the RS-485 port.

DigiRail OEE uses its RS-485 port as a Modbus TCP–Modbus RTU Gateway. (It can also be considered as an RS-485 to Ethernet converter for Modbus.) This allows Modbus TCP requests received over Ethernet or Wi-Fi to be transferred to Modbus RTU devices connected to the RS-485 line.

Example Application: Suppose you need an I/O module for AI, DI and DO signals in the field, and you also need to connect an energy analyzer with an RS-485 Modbus output to Ethernet. Normally, you would need both an Ethernet-enabled I/O module and an RS-485 to Ethernet converter for Modbus. DigiRail OEE combines these two requirements in a single device. While providing its own I/O data via Modbus TCP/IP or MQTT, it also bridges the Modbus device connected to its RS-485 port to the Ethernet network.

DigiRail IoT, on the other hand, allows its RS-485 port to be configured not only in Gateway mode, but also as a Modbus RTU Master or Modbus RTU Slave. In Master mode, it can read a total of 8 remote channels from Modbus RTU devices connected to the RS-485 line. These 8 channels do not mean 8 separate devices; they refer to a total of 8 different data points that can be read from the same or different Modbus RTU devices.

These Modbus channels can be transferred to higher-level systems via MQTT or Modbus TCP together with the data acquired from the device's own analog and digital inputs.

In summary, DigiRail OEE is suitable for monitoring its own I/O channels and performing Modbus TCP–Modbus RTU conversion, while DigiRail IoT provides a more advanced and flexible solution for applications that require data acquisition from Modbus RTU devices connected to the RS-485 line.

All of these settings can be configured easily using NOVUS NXperience, the free configuration software, either through the dedicated USB port available on DigiRail OEE and DigiRail IoT models or over the network.

What Exactly Is the Buffer Memory or Data Logger Feature in DigiRail OEE and IoT Models?

DigiRail OEE and DigiRail IoT models can store measurement and event data in the device's internal circular memory at defined logging intervals. This feature allows the devices to operate as limited-capacity data loggers.

One of the key uses of this memory feature is to reduce the risk of data loss during temporary network or broker connection interruptions when transmitting data via MQTT. If the connection is lost, unsent records are retained in the device memory and MQTT publishing queue. Once the connection is restored, the pending data continues to be transmitted via MQTT.

The devices can store up to 7,000 records. However, this value is not fixed for every application. Each record in memory contains the data from all channels that are active at that time. Therefore, as the number of active analog, digital and remote channels on the DigiRail IoT model increases, the size of each record also increases, reducing the total number of records that can be stored in memory.

For example, in a configuration with only one analog input enabled, approximately 7,000 records can be stored. In a configuration using two analog inputs and six digital inputs in counter mode, the capacity may decrease to approximately 1,800 records.

This memory is designed primarily to protect data during short-term network interruptions. The protection period depends on the logging interval, the number of active channels and the frequency of generated events.