MSP430 Temperature Logger – Part 4

Using the temperature monitor in the Incubator, I’ve run into a problem.

Temperature Monitor In Incubator

Temperature Monitor In Incubator

The problem is that the temperature seems to be fluctuating more than I’ve expected. Since we haven’t noticed any problems with the other thermometers, I’m going to assume that the problem is with my code. Perhaps it has something to do with my oversampling code? Do I need to average the samples better? Well, let us take a look at some data. Lets first look at the offending data here.

Wave Data

Wave Data

As you can see, it looks like the data is forming a wave. Is this something cause by the incubator itself. Perhaps noise on the ADC line? Lets look at some more data.

Missing Wave

Missing Wave

This is what the data looks like when the temperature logger is sitting around the house. Notice how it is missing the wave effect.

The following is roughly another 9 days with recording data at fifteen minute intervals. Notice how we still have the wave going on through out the data.

9 Days in Incubator

9 Days in Incubator

Well, after a lot of logging, it seems that we still have a problem. Now I decided, lets record more data, but let us record extra data points. So now instead of just storing the over sampled value, we will also store the average of the over sampled value, the non over sampled value, and the average of non over sampled value. The averages will be from four sequential readings. Here are the results from storing them once every fifteen minutes(so far all the temperature recordings have been taken at 15 minute intervals in hopes of storing an entire incubation period worth of data).

More Data!

More Data!

This new set of data seems to rule out problems with the oversampling; however, it does show that using averaging appears to provide some better results. This still leaves the question, are we still just getting ADC noise? To rule out getting a group of bad readings, let us try recording the temperature every minute and see what that looks like.

Every Minute

Every Minute

This appears to rule out getting noise on the ADC line; however, it does leave a few questions unresolved. Why do the other thermometers not report the same type of behavior? Is this just an problem of observing the analog thermometers at the right time? Is this a sensitivity issue? Perhaps the MSP430 calibration is off?

One thought on “MSP430 Temperature Logger – Part 4

  1. have you considered perhaps this is something to do with the incubator? Most of these cool to a certain temperature and then shut off until they are triggered again. perhaps your temperature control needs a bit of an adjustment.

    I’m running a very similar setup except in a fridge and noticed similar things. I got started with an MSP430 tutorial that got me started reading data. Then I store it in an external memory using the SPi interface and dump through USB.

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