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X-404 Modbus Master Controller | ControlByWeb
5 Year Warranty

Monitor up to 32 modbus devices/sensors as well as a 1-Wire Bus for Temperature and Humidity Monitoring



Temp: Up to 16 sensors

Modbus: Up to 32 devices/sensors


9-28 VDC*




Modbus Master Controller

Web Enabled

Up to 32 modbus RS-485 sensors.

Web Enabled

All logic occurs on device, no cloud necessary.

Web Enabled

Easily create custom logic, no scripting neccessary.

Web Enabled

Monitor sensor status using a standard web browser.


Share real-time sensor states with other ControlByWeb devices.

Logging and Graphing

Log and graph sensor states over time.

Email/Text Alerts

Customizable email/text alerts based on sensor states.

Other 400-Series Features

Task Builder, encryption, intuitive user interface, much more.

Industrial Internet of Things (IIoT)

Monitoring RS-485 Sensors

The X-404 module functions as a web-based Modbus master controller and monitor for third-party RS-485 modbus sensors and devices. It can monitor up to 32 sensors. Reap the benefits of modbus integration with easy setup, reliability, and daisy-chaining capabilities.

Control Options

All ControlByWeb devices, with their various combinations of inputs and outputs, can function as a Modbus/TCP slave device controlled by the X-404 controller.

Fluid Level Monitoring

Use the X-404 to monitor fluid levels through the module's Modbus protocol.

Remote Monitoring

The X-404 can be connected to and monitor up to 32 different modbus devices. In this illustration, the X-404 is connected to the MPX Float Sensor, as well as the MND Modbus Display for local level monitoring. The X-404 can also be connected to pressure sensors, like the PT-500 for other level monitoring options.


The X-404 module is designed to automatically program modbus sensors when connected, without using an external power supply or separate programming module.

Email/Text Alerts

Configure the X-404 to send email/text alerts when the level reaches user-defined high/low paramaters. Enable logging to record the history of sensor states.


  • Connect up to 32 modbus devices/sensors
  • 1-Wire Bus for up to 16 sensors (temperature, humidity, etc.)
  • Monitor,log, and control up to 32 remote modules, or up to 100 I/O
  • User Permissions: Admin, Manager, User
  • Tasks
    • 50 Scheduled
    • 50 Conditional
    • 20 Override Schedules
  • Send email alerts based on user-defined conditions (supports encrypted email servers, such as Gmail)
  • Real-Time Clock with NTP server synchronization
  • Automatic daylight savings and leap year adjustment
  • No software required
  • Customizable web-based Control Page
  • BASIC script support for advanced flexibility
  • Configurable logging
  • Graphing (logged data)
  • HTTPS/TLS encrypted
  • Static or DHCP IP address configuration
  • Modbus, SNMP, Remote Service, IP Filtering
  • Field updatable
  • Rugged DIN-Rail/wall-mountable enclosure
CE listed RoHS compliant Made in the USA

X-404 Part Numbers (Differences highlighted in green)

X-404-I Temp: Up to 16 sensors.
Modbus: Up to 32 devices/sensors
Task builder, email daily log file, add 100 I/O on up to 32 Remote I/O Modules 9-28 VDC

More Information:


Where to Buy

Click "Buy Online" to view part numbers and pricing. X-404 is available in the USA and internationally, and can be purchased either from us or an Authorized Distributor.

Warning: May contain chemicals, including Nickel (metallic), known to the State of California to cause cancer and reproductive harm. -