Bad Temperature Sensors?


(Hfb) #1

I have been plotting the temperature throughout my house and have noticed that a few of my multi sensors seem to have lower resolution than the others. Here’s an image to show that difference.

If you look at field 2 and 6, they show lower resolution than the other charts. Some of it is very likely because of the scaling on the Y axis but even then, compared to field 3, they are still lower resolution when the scale is the same.
Any ideas why this is the case?


(Pmsmaker) #2

There is a know problem with readings.
Mine were off like 5-6 degrees.
A calibration fix is supposed to be in the works … some time ago.
IMO that is not an option because if it were that easy it would have been done already.
Keep on it and let us know.


(Hfb) #3

The calibration isn’t an issue in this case because I compensate for it in my Python script so all the temperatures above are good and all agree with each other as I did some testing with each sensor and made them all “equal” to each other.
The issue I’m seeing is the lower resolution with the temperature changes. For the ones in question, there is ~1 degree F resolution while the others are around 0.5 F resolution when there are changes.


(Pmsmaker) #4

OK, I am no expert. May be the result of device/part binning.


(Minollo) #5

As mentioned elsewhere, I had to give up using the ST temperature sensors due the unreliable and erratic readings.
I ordered a FortrezZ temperature and water unit; hopefully that will work as it should.


(Hfb) #6

What do you mean by device/part binning? My thought was that they possibly used a different temperature sensor in them that have lower resolution. I could always take it apart and check for them but I haven’t gotten to that point yet.
At some point, I’ll be using LM35 sensors with my own XBee radios to do similar work.
On a side note, one of my accelerometers on my multi isn’t working now either. It could be a low battery but it’s still at 35%.


(Chuckles) #7

To me it looks more like a communications issue than a sensor resolution issue.

The horizontal plateaus are where the system is unable to get an updated reading so it keeps plotting the last known value. When it does finally get through and gets a new value, it is substantially different to the prior value and hence the large vertical step.

Where are the two affected sensors located? What happens if you move them (temporarily) closer to the hub?


(Hfb) #8

Good catch there. It is indeed because it’s not updating but I’ll have to move the sensors around some and see if that makes a difference. I don’t think it will because some of them aren’t that far from the hub but it’s definitely worth a shot.


(Hfb) #9

I tried moving one of the sensors and it didn’t seem to really change anything much. RSSI levels went up some and back down when I put it back after I got up this morning but looking back as the past history, RSSI levels were just as high as when it was close at times in the past.