Problem with my 1-Wire

Since I added a long run of cable and 2 new sensors, I have been noticing some strange temperature readings.  Every once in a while, the reported temperature will spike up off the graph.  I have seen this on every sensor and sometimes it seems to happen several times within a short period of time.  Here is an example of what it might look like from yesterday:


click to enlarge

I have seen this maybe a dozen times.  The first few times I assumed it was a fluke and manually deleted the values from the database.  This is obviously not the best practice but I couldn’t imagine what was happening and just decided to ignore and hope it went away.  When the problem didn’t go away, I stopped deleting them in hopes of finding a pattern.

This is the SQL query I ran to find (and eventually delete) the offending entries.  The temperatures are all saved in one table of the database and I am looking for temperatures greater than 50ºC (122ºF).
SELECT * FROM temps WHERE temperature > 50 AND reading_time > date '2014-10-15';
When I run this query right now, PSQL returns:

         reading_time      |   location   | temperature
2014-10-16 22:17:27.265155 | outside      | 85
2014-10-19 14:32:56.26111  | outside      | 85
2014-10-19 14:44:06.480761 | outside      | 85
2014-10-21 16:50:26.453891 | dining_room  | 85
2014-10-21 20:22:55.547973 | back_bedroom | 85
2014-10-21 20:23:56.437617 | back_bedroom | 85
2014-10-21 20:24:57.342779 | back_bedroom | 85
(7 rows)

What I immediately notice is that all of the out-of-range values are all the same.  85ºC.  This can’t be simply a coincidence.

I am going to do some research about this and get back to you.

  1. Problem with my 1-wire found | Gouhobandgraw - pingback on 2014-10-29 at 10:04

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