Hey, Any change that you can get the low temperature below-40 ? Up here in Alberta, Canada today we got a -45 wind-chill or feels like and in some places air temp. is below -40 too.
the battery can work at pretty low temperatures, but -40 is a bit of a stretch. Who knows you might get lucky.
It still works at that temp, its just that it doesnt read or displays anything lower then -40
luckily it never gets that cold over here. I guess it is the temp sensor itself that doesn’t report temperatures below -40.
Southern Saskatchewan here. Regular thermometer is -40 but the Weatherflow/Tempest stopped showing a temp when it hit -40. Graph went off the bottom and a blank — appears where temperature reading should be. Is this normal? Batteries say good, other things seem to be recording. In original post mlandfarm above was talking windchill. This is real is temperature.
looks like the sensor limit is -40 in both air temp and wind chill, does guys down south ( where they build the stations) probably don’t know what -40 feels like Ha Ha
Midnight here. Still at -41 on old fashioned thermometer.
@WFstaff @WFsupport Came here for the same reason. The station is ARTIFICIALLY limited to -40C. I understand that it is only calibrated to read up to -40C, but it would be great if there could be a switch to allow for displaying of temps lower than -40C with a disclaimer stating that those temperatures might not be accurate as it is only calibrated to -40C. Similar to how there is a power saving switch in the settings…
Last night the temperature dropped below minus 40 and once again the thermometer stopped displaying. I am resigned to that reality now. It would be fun to have it display at colder temps so one could see what the windchill is locally.
From the top of my head I think the temp sensor can’t go below -40°C though we mention -37°C as lowest (between those 2 values the error margin becomes so big not even sure what you get) . Not to bad for a home device I would say.
does anybody know what chip is used inside to measure the pressure (which probably reports the temperature as well)?
why do you claim this is artificially done? It might just be that the sensor chip itself never reports values below -40.
At one point, they were using the Bosch BME-280 for pressure, which is only good to -40 (F/C) per the spec sheets.
Temp/humidity was using the Sensiron SHT21 at one point, which is likewise also only good to -40 (F/C) per its spec sheet.
The SHT21 is common in several other PWS models, including the Davis VP2 which is also only good to -40 (F/C)…
Correct. The chips are calibrated to -40C but will report below -40C, however it might loose accuracy below -40C as they are not calibrated for those temps. @vreihen Like you mention the VP2, is also only spec’ed/calibrated up to -40C, however they will continue to report below that temp. Hence it is artificially limited in the weatherflow model, either in the firmware or the software. @sunny @WeatherFlowStaff
are you confusing operating range with the reported range values? I can find that the operating range of the chips starts at -40. Below that, nothing is guaranteed. But that doesn’t mean the chip tells you values below -40. it might be the zero value of the adc is set to -40.
I am not confusing anything with anything. The chip is capable of reporting values below -40C, however it is outside its official certified range. Weatherflow has decided to not report these values either via the firmware or software. There’s only so many manufacturers of temp chips (for this application) which are certified up to -40C, however the chips will report below them, but there is no accuracy guaranteed.
It would be nice if @WFstaff or @WFsupport could at least acknowledge and/or speak to this issue.
As I understand, to prevent invalid temperatures from being shown, the graphs should not display any temperature data below -40 F/C. However, it seems there are some inefficiencies handling the null data, where it appears it’s being plotted at -40 F/C. Ideally the line should not be present and there should be no data points.
It is a hardware limitation, not an artificial limitation. You are correct it was decided to not display values outside of the hardware spec. because they are invalid, untrustworthy data. On that note, real-time Nearcast data should be able to take over where the hardware has limitations.
its a difficult problem. indicating that the temperature is below -40 surely is better than no data at all. I agree that it makes almost no sense to display untrustworthy data, but some indication in the graph that the temp is below -40 (or above 60) is appreciated. Perhaps use some shading of the graph area below -40 and display the untrustworthy values anyway.
Ummm no. What if the sensor goes whacko and thinks it is ‘above’ the measurable range ? It happens.
I could see some indication somehow of ‘bad data’ perhaps but that might be hard to do in their gui and of very minimal value over their customer base…
but how would you know… if it goes wacko because it is -55 and it reports +10. There is no way to tell the difference between wacko +10 and real +10 (unless the sensor has a special flag for out-of-range data)