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.

X-404 connects to many different sensors

The X-404 monitoring fluid levels through Modbus



  • 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

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

Power Requirements

  • Voltage:
    • X-404-I: 9-28 VDC
  • Max Current:
    • No Modbus Sensors: 134mA
    • X-404 + 1.7A for modbus sensors: 1.834A

    See users manual for more information

RS-485 Connector

  • Sensors Supported: Up to 32
  • Connector: 5-position, removable terminal strip, 3.81 mm spacing
  • Communication: RS-485

Temperature Sensors

  • Maximum Number of Sensors: 16
  • Temperature Range: -67°F to 257°F (-55°C to +125°C)
  • Accuracy: ±0.5°C (from -10°C to +85°C)
  • Sensor Functions: Monitor Temperature, Log Temperature, Email Alerts, SNMP Traps
  • Humidity Type: Xytronix Model X-DTHS-P sensor
  • Humidity Range: 0-100% RH
  • Accuracy: ±2%
  • Max Cable Length: 600 feet (180m) maximum combined cable length

Real-Time Clock:

  • Manual or NTP(Network Time Protocol) setup
  • NTP Sync Period: Once, Daily, Weekly, On Powerup
  • Auto Daylight Savings Adjustment
  • Battery (capacitor) Power Backup

Capacitor Power Backup

  • Backup Functions: Real-time clock, 1 register, 2 counters, 64 relay states (remote modules only)
  • Backup Duration: 2 week minimum


  • Type: 10/100 Base-T Ethernet Port
  • Setup: Static or DHCP IP address configuration


  • Modbus Bus: 5-Position, 3.81mm terminal spacing, Removable. For 16-28 AWG wire.
  • Power and 1-Wire Bus: 5-Position, 3.81mm, Removable
  • Network: 8-pin RJ-45

LED Indicators

  • Number of LEDs: 3
    • Power on
    • Network linked
    • Network activity


  • Operating Temperature: -40°F to 150°F (-40°C to 65.5°C)
  • Size:
    • 1.41in (35.7mm) wide
    • 3.88in (98.5mm) tall
    • 3.1in (78mm) deep (not including connector)
  • Weight: 5 oz (142 grams)
  • Enclosure Material: Lexan 940 Polycarbonate Plastic
  • Enclosure Flame Rating: UL94 V0


  • HTTP, HTTPS, SSL, XML, Modbus TCP/IP, SNMP V1,2C,V3, SMTP, Modbus RS-485


    • Log File Size: 3,072-Kbyte (up to 50,688 logs)
    • Storage: Nonvolatile Flash
    • Buffer Architecture: Circular Buffer

Log data can be periodically stored on a computer via FTP or email.

Advanced Features

  • Task Builder
  • BASIC interpreter (up to 4-Kbytes script file size)
  • Remote services

Password Settings

  • Password Length: 6-18 Characters

Electromagnetic Compliance

  • IEC CISPR 22, CISPR 24
  • EU EN55024, EN55022
  • X-404-I: FCC 47CFR15 (Class B)

Product Safety Compliance

  • UL 61010-1 (Electrical Equipment for Measurement, Control, and Laboratory Use)
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