Remote Temperature Monitoring with Linux

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Use a small footprint Linux with some cheap hardware to create a remote temperature monitor.
Future Extension

Digital multimeters are general-purpose electronic measurement tools. Although I used a thermistor for temperature measurement in this application, you can use other sensors that have resistance, voltage or electrical current as outputs. Some other conditions to measure include flow, pressure, weight, light level and humidity.

You don't need more multimeters to measure more than one temperature. You can connect a single multimeter to a switching device. You then would create a script to operate the switching device, which allows you to select one temperature sensor at a time.

Conclusion

This example shows how the tool concept behind Linux works for solving applications where cost and flexibility requirements are important. The wide variety of distributions available compared with other operating systems meant developing a system with all the features needed was practical. Additionally, you can add features using Perl and the development environment provided by the University Linux distribution.

The system can be duplicated for less than $100 US. The multimeter, thermistor and wiring accessories are available from numerous electronics retailers. Many retailers have Web sites, so it's easy to compare features, specs and pricing before ordering. Purchasing a used digital multimeter should be done with caution, as there is no easy way to tell whether accuracy of the instrument has been affected by the previous use.

Resources for this article: /article/8833.

Steven M. Lapinskas has a professional background that includes the areas of software quality assurance, mechanical design and project management. Some of his free time is spent experimenting to interface Linux with the real world outside the computer.

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Try ipmitool

Anonymous's picture

Try ipmitool - read the man page.

Linux Temperature Sensor

Jeff Pile's picture

I know this is an old post, but if your looking for a temperature sensor to use with Linux, try a google search for DirecTemp or contact Quality Thermistor.

They have a virtual serial version that works well.

Alternative solution

Anonymous's picture

Nice article about connecting digtal multimetr to Linux box. In the case you just want to measure temperature, you can find several other solutions on the web. One of them is
http://www.digitemp.com/
That one uses network of digital temperature sensors (DALLAS DS1820). From my point of view it is cheaper and more better solution for your needs and you don't need to solve "ugly" DTR/RTS hacks.

Other similar projects to connect sensors with I2C or Dallas interface to serial or prallel port exists as well...

RTS?

Anton's picture


If I connected the multimeter serial interface cable RTS to the RTS pin of the second serial port, the multimeter would be faked into seeing the correct line setting.

Why not just tie RTS to ground to pull it low?

You can't assume that everyone has a second serial port or that it won't be initialized, sending that RTS line high too.

DTR, RTS & Linux

Anonymous's picture

DTR & RTS signals, are you kidding? Yes, I know these signals are not supported well in Linux. You selected nice hw workarround. I selected hardware workarround in the past too.

Windows users don't need such workarrounds. Why Linux should? Why everyone only uses hw workarround and doesn't fix it in proper way in driver and user utilities? Are developers in Linux world just ignorants? I understand why Linux don't have (open source) NVidia and ATI drivers, and drivers for special hardware (like WiFi cards, etc). But I don't understand why problem with RTS and DTS on serial ports wasn't solved long time ago...

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