Hi,
I've had some sensors attached to my emonTX V2 for a long time giving me consistent readings.
Recently I've added an ESP8266 board with a couple of sensors attached and have noticed that from time to time one of the readings will increase and then decrease by as much as a degree. The time between these changes can be 8 hours or more at least.
Sensors in both cases are powered, i.e. they have power, ground and data connected.
Anyone run into this before? Or is it just a duff sensor?
Thanks for any insights.
Re: DS18B20 sensor - sudden change in readings
Are there any fluctuations in the power supply? WiFi is allegedly a large current consumer ("you'll want to assume the ESP8266 can draw up to 250mA so budget accordingly" to quote Adafruit), so that's where I'd start looking.
Re: DS18B20 sensor - sudden change in readings
Thanks Robert. I had wondered about that but could only see issues on a Google search when voltage dropped below about 2.5v and the esp is on a 2A USB power supply. So I'm assuming that's not the case.
I'm not near the thing for a few days but will have to try another supply after I've tried swapping out the sensor for a new one.
Re: DS18B20 sensor - sudden change in readings
The sensor could well have died, but I would expect it to either give nothing, or totally stupid readings if it had.
Another thought, is there any self-heating going on?
Re: DS18B20 sensor - sudden change in readings
Hi Robert,
No self heating. It's in a pocket in the heat bank. You can see the temperature slowly dropping and then suddenly either jumping up or down by about a degree. These instances are well separated time wise. I have a good graph of one instance where they are 8 hours apart.
Once I'm back next week I'll take a screen shot of the graph and post it, also a zoomed in image of the actual change.
Simon