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SRM showing incorrect temperature

Old 05-19-16, 12:52 AM
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UmneyDurak
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SRM showing incorrect temperature

Hi.

My SRM computer started showing wrong temperature, but the zero offset doesn't seem to be affected. Anyone ran in to this issue?


Thank You
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Old 05-19-16, 07:10 AM
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My temperature reading seems to always be off by a bit. However, I suspect that the "bit" is consistent (i.e., the system is likely reliable), and, thus, I don't get too concerned about it. But, consider contacting SRM for the scoop on that.

Originally Posted by UmneyDurak
Hi.

My SRM computer started showing wrong temperature, but the zero offset doesn't seem to be affected. Anyone ran in to this issue?


Thank You
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Old 05-19-16, 08:41 AM
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Yeah I emailed them. Will call today. It was showing correct temperature until last week. Now it's shows -70C. Bleh.
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Old 05-19-16, 08:58 AM
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Originally Posted by bostongarden
My temperature reading seems to always be off by a bit. However, I suspect that the "bit" is consistent (i.e., the system is likely reliable), and, thus, I don't get too concerned about it. But, consider contacting SRM for the scoop on that.
the best thing about SRM's design for the power meter (IMO) is that it is largely immune to temperature changes. other companies sell software 'temperature correction', while the SRM has none. it doesn't have to; the orientation of the strain gauges is such that temp fluctuations due to difference response rates of the materials cancel out. (a 50F swing in a day is pretty common for me from where i store the bike to where i ride.)

i realize we're talking about the head unit here, but i just wanted to be clear that nothing about the power reading would be affected.




Originally Posted by UmneyDurak
Yeah I emailed them. Will call today. It was showing correct temperature until last week. Now it's shows -70C. Bleh.
in your original post i wasn't sure if you meant "off by a few degrees"; i've always found that head units display temperature that is off by a bit--either due to being in the direct sun (vs ambient temp) or that the sensor is placed near a circuit which heats it up just a bit.

but....... -70C? we're not on mars!
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Old 05-19-16, 01:23 PM
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Originally Posted by tetonrider
the best thing about SRM's design for the power meter (IMO) is that it is largely immune to temperature changes. other companies sell software 'temperature correction', while the SRM has none. it doesn't have to; the orientation of the strain gauges is such that temp fluctuations due to difference response rates of the materials cancel out. (a 50F swing in a day is pretty common for me from where i store the bike to where i ride.)

i realize we're talking about the head unit here, but i just wanted to be clear that nothing about the power reading would be affected.






in your original post i wasn't sure if you meant "off by a few degrees"; i've always found that head units display temperature that is off by a bit--either due to being in the direct sun (vs ambient temp) or that the sensor is placed near a circuit which heats it up just a bit.

but....... -70C? we're not on mars!
Ah thanks for explanation.
I called SRM tech support and zero offset is adjusted based on a current through the strain gauges. It does not rely on the thermometer in the head unit. Looks like that part glitched. So it's showing -70C. I'll probably just send it in after racing season since it doesn't affect power readings.
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Old 05-19-16, 08:25 PM
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Originally Posted by UmneyDurak
Ah thanks for explanation.
I called SRM tech support and zero offset is adjusted based on a current through the strain gauges. It does not rely on the thermometer in the head unit. Looks like that part glitched. So it's showing -70C. I'll probably just send it in after racing season since it doesn't affect power readings.
yeah...SRM doesn't promote a bunch of things that are good about the system, and instead when other companies say things like "we've got temperature compensation" they position it as something great. SRM's lack of response comes across as weakness when the reality is that it's a weak hardware design that requires compensation.

anyway....that sucks about the temperature problem in the head unit. i bet they all have the same cheap chip for that.

is it off in a linear way or random?
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Old 05-19-16, 08:36 PM
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Originally Posted by UmneyDurak
I called SRM tech support and zero offset is adjusted based on a current through the strain gauges. It does not rely on the thermometer in the head unit.
Originally Posted by tetonrider
yeah...SRM doesn't promote a bunch of things that are good about the system, and instead when other companies say things like "we've got temperature compensation" they position it as something great. SRM's lack of response comes across as weakness when the reality is that it's a weak hardware design that requires compensation.
The resistance of the strain gauge will vary with temperature. Not relying on an "actual thermometer" does not mean there is no compensation.
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Old 05-19-16, 09:52 PM
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Sheesh ... all I see on here lately is SRM bad news. So glad I've got my Quarq
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Old 05-19-16, 10:13 PM
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Originally Posted by Enthalpic
The resistance of the strain gauge will vary with temperature. Not relying on an "actual thermometer" does not mean there is no compensation.
Sorry...thought it was implicit in my earlier message that there are brands promoting *software* compensation. When I read it back I realize that it was not clear that some companies either did not take into account, or they did so ineffectively, this variation in their HW design.

It's also interesting to note that some of them only recently added this. What was going on before they figured out it was necessary??

better to solve something with proper hardware design vs having to make up for a deficiency via software.
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Old 05-19-16, 10:14 PM
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Originally Posted by hack
Sheesh ... all I see on here lately is SRM bad news. So glad I've got my Quarq
If it's a known-good unit, keep it! Not all quarqs are bad, nor are all SRMs good, of course. We're just talking percentages.
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Old 05-19-16, 10:46 PM
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Originally Posted by tetonrider
yeah...SRM doesn't promote a bunch of things that are good about the system, and instead when other companies say things like "we've got temperature compensation" they position it as something great. SRM's lack of response comes across as weakness when the reality is that it's a weak hardware design that requires compensation.

anyway....that sucks about the temperature problem in the head unit. i bet they all have the same cheap chip for that.

is it off in a linear way or random?
It's fairely consistent -74C. I think sensor went out completely.

Originally Posted by hack
Sheesh ... all I see on here lately is SRM bad news. So glad I've got my Quarq
Dude I have special touch. As in I touch technology and it breaks. lol
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