Moderators: Doone, westonwarrior
haydn callow wrote:these types of sensors are calibrated to be at their most accurate at 25C.....any error at 25C will expand as the temp rises.
i.e. 1C error at 25C will be 3C error at 75C....think I have that right.
Thermistors can be bought +/- 0.5%.......+/- 2% ect
The more accurate the more expensive.
As long as you know the error you can work it out and live with it.
Firstly, you are probably correct in your guess that these are 10k thermistors. A quick check gives resistances around 12kohm in our office in chilly Scotland, so room temp is at best 20 deg C.haydn callow wrote:I thought a 5% error at 25C would also be 5% error at 75C ???
Probably not understanding it properly
No!haydn callow wrote:This leads me to something I’d like clarified if anyone can – if a thermistor is specified at 10%, is it likely to be within 10% at all temperatures?
Good questiom....
defo +/- 10% @25C
How this affected at higher temps I do not know...If it is still 10% @ 100C there could be quite a error.
As you say Thermocouples are the way to go
Could not agree more.tallbongo wrote: Jaylee has sourced a potential temp monitoring solution for under a tenner. This could save many Bongo heads and we should be trying to get this to work.
(edited to take the last frustrated couple of words out!)
Jaylee has put quite a lot of effort into this (a lot more than you see in this thread) and he should be applauded for that.
The academics of the electrical/thermal properties of the sensors being used in this system is educational, and I find it really interesting - well done for the research into this. The fact that there will be some error introduced is easily tolerable, but not to be ignored. I don't think this in any way discredits the find, or that anyone is trying to. It's a steep learning curve - although not steep enough at higher temperatures it would appear!Driver+Passengers wrote:That sounds promising!bikerbob wrote:... they have admitted to a software error.
Driver+Passengers wrote:
I think the software error that the supplier has admitted to is far more relevant, in terms of identifying the cause of the "wild" values we're seeing. As for 10%, 5% or whatever, you'll soon learn to compensate in reading numbers off and know what's "normal". It can't fail to be a good thing here.
I'm with you on all of that. Presumably, an item quoting X% error more reflects the tolerance of the manufacturing process than the average performance you should expect from a part - nothing is to say a given unit may not infact read accurately. The variation in readings from a large enough sample set of thermistors probably follows a normal distribution centered around "correct" with the tails up to the quoted +- value. However this theory is still is missing the point that "accuracy" may change over the temperature range (ie non-linear). The response curve of the 10k thermistor suggests that for the temperature range we're interested in (75-100C?), we might be "better off" with a different value thermistor in order to get a steeper gradient curve in our preferred temperature range. I say "better off", but you can't get much better off than finding a cheap unit like this. Other than the software issue, should perform perfectly adequately in a Bongo.tallbongo wrote:Driver+Passengers wrote:
I think the software error that the supplier has admitted to is far more relevant, in terms of identifying the cause of the "wild" values we're seeing. As for 10%, 5% or whatever, you'll soon learn to compensate in reading numbers off and know what's "normal". It can't fail to be a good thing here.
Exactly. And remember it has not been established that these probes are +/- 10%, +/- 5% or whatever. All that has been measured is that they are likely to be 10Kohm nominal resistance.
The manufacturer claims +/- 1 deg C accuracy. There is no sound reason to believe that the probes are not +/- 3% which would meet this. The retail cost is only 50p per probe more than 10%. I'm sure they are getting them massively cheaper than we can.
The only evidence that they may not meet this is the very crude test I did last night to check out if I had the display problem. I'll freely admit there is a lot of doubt over whether this was a valid trial.
However, checking out the theoretical response shows that even if they do not meet the manufacturers claims, even the cheapest thermistors would not be a disaster providing the display unit is designed with suitable care.
Internal/external air temp, hose stubs, exhaust, etc...? If i could get a long enough probe wire....? I would like to monitor the temperature in my house..!Driver+Passengers wrote:
To end with a question, if you had 10 sensors to distribute around the van in a non-invasive way, where would you put them all?
Aye - one in each room!jaylee wrote:If i could get a long enough probe wire....? I would like to monitor the temperature in my house..!Driver+Passengers wrote:
To end with a question, if you had 10 sensors to distribute around the van in a non-invasive way, where would you put them all?
I've had another 2 emails from Sure since yesterday. The first basically repeated that I'd get another gauge when they fix the problem. The second sent 8 hours later looks like delivery tracking information, although I can't get any information from the reference they gave me.bikerbob wrote:ResultReceived email from seller, has offered to replace the unit FOC no prompting from me but I did request that all connections & sensors be included to ensure a"clean" installation, will advise results when new unit has been insatalled.
Regarding the accuracy of the temperature read out, I`m was not too concerned with the accuracy of the temps although would be good if they were, bought the unit to inform if temps exceeded my highest normal running temp readings, perhaps I`m being nieve Haydn. How do you fit new thermisters to replace the originals and where can they be purchased fromt, as you are probably aware I`m flying by the seat of my pants on electricals etc.
