Toll Free Sales


Email Sales!
View Cart

Temperature Guard has been making quality products since 1977. We currently specialize in Food Service, Medical, and Industrial grade applications. We offer quality products from a family business.

Refrigerator/Freezer NetGuard - M303

  • Monitor 2 temperatures and 2 doors
  • Quick setup
  • Continuous temperature data logging
  • Stores up to 4 months worth of temperature data
  • Access temperature data with a web browser from anywhere
  • Rechargable battery backup


Order $250.00

Order with 2 year NIST Cert +$30

  • Description
  • Features
  • Web App
  • FAQ
  • Specifications
  • Sensors

The M303 helps protect the valuable contents of your refrigerators and freezers by continuously monitoring the temperature.  The M303 will notify you of a temperature issue with its built in audible alarm and our free Data Capture software will send an alarm email, specifying the cause of the emergency.

The M303 monitors and logs the temperature data to its internal memory, independent of a PC.

The M303 will continue to log temperature data for days without power running on its own internal rechargeable battery backup.

Store up to 4 months worth of temperature data, the data is never lost.

Why waste time and money with a messy paper chart recorder.  With the M303 you never have to change pens or replace chart paper.  If there is ever a temperature issue, download the temperature data from the on board memory into any any browser then generate a chart or export the data to a CSV file.

Our free Data Capture software simplifies your temperature recording tasks by automatically recording the temperature status of all of your M303 on the network.   Data Captures displays the real time temperature in an easy to read grid and stores all readings to the PC where you can generate charts and reports.

  • Built-in Ethernet connection with web server.
  • Onboard data storage with Embedded Real Time Clock.
  • Local audible alarm.
  • Relay output for connection to existing security system
  • Programmable high and low temperature limits for each refrigerator/freezer.
  • Programmable time delay for each refrigerator/freezer.
  • Data Logging Capabilities.

View the temperature data

Graph and print the temperature data


What is the minimum I need to buy to build a monitoring system?

  1. One M303.
  2. One temperature sensor for each area to be monitored.

How does the M303 work?
The M303 is designed to monitor two sensors, one for the refrigerator and one for the freezer or any two zones you like.

You connect the M303 to your Ethernet network and the sensors.  You then use our Data Capture software to program the M303 and collect the temperature data to a PC.

When a sensor goes out of limits, the M303 will sound it's alarm and Data Capture will send out alarm emails and or text messages.  Data Capture has to be running on a PC for the emails to be sent.

The M303 maintains a temperature log file of up to 60 days worth of data.  This data can be downloaded with a web browser.


  • Temperature Sensor Range: -148°F to 96°F, -100°C to 35°C
  • Measurement resolution:  0.1°
  • Sensor Type: 1000 Ohm Platinum (.00385 TCR)
  • Maximum Temperature Inputs: 2     Need more temperature inputs?
  • Maximum Door Inputs: 2
  • Internal Memory:  124 days at one 60 minute update rate
  • Internal Memory Data Update Rate: Programmable 1 to 60 minutes
  • Network Interface: Ethernet 10Base-T or 100Base-TX (Auto-Sensing)
  • Network Connector: RJ45
  • 0.5a 125vac alarm relay output
  • Internal alarm buzzer
  • Rechargeable battery backup included keeps the M303 operating for up to 10 days.
  • Internationally compatible plug-in wall transformer included (100-240v 50-60hz) Standard US plug.
  • Operating Temperature Range 32°F to 125°F
  • Enclosure Dimensions: 5.625" x 3.250" x 1.375"

The M303 can be used with our temperature sensors in either glycol or glassed filled vial. See Sensors and Accessories page for more details.

You can also use the Door Sensors and the Strobe light (RL-B)