Guide to using SNMP with your Room Alert 3E

SNMP is a great way to integrate your environmental monitoring system into your existing network management system. This guide provides a short tour of all the information you can access via SNMP from your Room Alert 3E.

A Short Introduction to SNMP

The Simple Network Management Protocol is a standard for querying, setting and alerting a wide variety of management information from a device. There are two main system components in SNMP. The first the the SNMP agent. The agent is the entity that responds to queries and optionally send alerts in the form of SNMP traps. The SNMP client requests information from the agent and then logs the data as necessary. A standard network protocol means it doesn't matter what operating system you are running, you can interact with any other compliant SNMP agent from any SNMP client.

If you want a fuller explanation of SNMP, please read the Guide to SNMP?

SNMP on the Room Alert 3E

The Room Alert 3E supports SNMP version 1. If you try to use the Room Alert with a higher version, like 2c or version 3 you will likely get a response like Timeout: No response from .

The Room Alert 3E has two ways to format the sensor readings. You control the sensor reading format using the admin portal built-in to your Room Alert 3E. Go to the Settings > SNMP section. Enable the Use 2 digit SNMP property to round the sensor reading to two digits or disable to use 4 digit SNMP values. The default is set to 4 digit SNMP values.

Room Alert 3E SNMP Settings

How to Retrieve Data Using SNMP

There are many different tools to retrieve SNMP data from your Room Alert 3E. I've chosen net-snmp mainly because it is free and available for pretty much any operating system.

To retrieve information from your Room Alert 3E, type the following into your command prompt:

snmpget -v 1 -C public  ip-address oid 

In my case, my Room Alert 3E is on my network at and I want to retrieve the internal temperature in Celsius so I typed in the following:

snmpget -v 1 -C public .
SNMP Request & Response

You are probably wondering why the temperature data returned looks a bit odd. SNMP v1 can't represent the temperature as 23.93 so it needs to represent it as an integer instead. Simply divide the number by 100 and then you'll get back to the real temperature.

To find out what data is available via SNMP from your Room Alert 3E, please see the tables in the Available Information via SNMP section below.

Available Information via SNMP

Internal Temperature Sensor

The internal temperature sensor is located inside the case of the Room Alert 3E. The sensor is always present and cannot be switched off.

Description Full OID Type Example Value
Current temperature in Celsius . Integer 2393
Current temperature in Fahrenheit . Integer 7507
Label . OctetString Internal Sensor
External Digital Sensor

The external digital sensor is connected to the Room Alert 3E using the RJ-11 connector. When the external digital sensor is not connected the Room Alert 3E will not respond when you request the values below.

Description Full OID Type Example Value
Current temperature in Celsius . Integer 2443
Current temperature in Fahrenheit . Integer 7507
Current relative humidity . Integer 5148
Current heat index in Fahrenheit . Integer 7597
Current heat index in Celsius . Integer 2442
Label . OctetString Ext Sensor 1
External Switch Sensor

The external switch sensor connects to the Room Alert 3E using the two pin connector terminal. Whether a switch sensor is connected or not, the Room Alert will respond to the values outlined below.

Description Full OID Type Example Value
Switch state . Integer 0
Label . OctetString Switch Sen 1

This article was written using a Room Alert 3E with software version 2.0.0. Prior or later revisions of the software may vary. I would urge anybody running version 2.0.0 to upgrade to the latest firmware as at least one bug has been fixed with the MIB files. You may struggle to compile the Room Alert 3E MIB file if you use the Room Alert 3E version 2.0.0 firmware. I used Net-SNMP version 5.7.3 to explore the SNMP data on my Room Alert 3E.

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