4iiii precision power meter, my experience

[softy]

trolling through all the research, it appears to me the best power meter on the market is the infocrank.

Duck for the flak!

Why?

No calibration needed, this unit is designed to be stable across temperature ranges and is extremely stable due to the wheatstone design of the strain meters in each crank. I won't explain the theory but this is a common way to balance errors in accuracy measurements of all kinds (a proved technique), not just for watt meters. It also measures both legs so no doubling of watts, which is always going to be an estimation.

the only drawback is it is towards the upper end of the price market, so I need to save..... 2K about.

Not sponsored or have any relationship with this company, it comes down to me realising, if you want to measure watts, you need to be able to measure watts consistently in all conditions, otherwise how do you compare your performance? Many units don't do this.

[dalai47]

Pull that blurb straight from their site?

The use of a wheatstone bridge is not unique to the Infocranks, SRM have used that configuration for 30 years!

[softy]

no I didn't just pull it from there blog, I actually understand and have used the concept.

SRM may use it as well, I can not confirm or deny, as I dismissed this product due to the significant price. But most power meters don't and require zeroing due to drift before every ride (PITA)
I have also used Wheatstone bridges for accuracy testing of electrical metering units. It is comprised of 4 components placed in a diamond configuration, the ratio of one side is the same as the other, any variation in one of the elements creates a spill current across the centre of the diamond. this current is monitored and represents an error change. This can then be related to a correction. This is related to ratio change between the two sides of the variance in the ratio. This can be caused by temperature or be a comparison method with a known standard (of one side).

It is a reliable and known system of accuracy which has been used for decades.

What good is a watt meter that drifts or needs to be re-zeroed every time you ride. This means it is not consistent. Therefore how do you know you were putting out more watts today than yesterday?

It also can't be compared to anyone else or another meter.

In the accuracy world, drift is a big thing, if you say a meter measures watts, it has to have corrections for different points of measurement. this whole argument that as long as it is out consistently is just rubbish, because no meter is linear across its measuring range. i.e. if you have a tape measure, the percent error measuring a centimetre is far greater than measuring 10 metres. so error always varies across the range. An example on a power is it may have a small error at 400watts but a big error at 100watts and all this may vary with temperature or any other variable that effects accuracy.

So without some known measurement of compensation it is a guess, which is actually what most do.

[dalai47]

I would much rather manually calibrate and be able to recalibrate during a ride to know my data is accurate rather than the unit have some form of algorithm to cater for temp fluctuations.

My SRM's are all bomb proof and all bought used for far cheaper than the Infocranks. I am able to manually measure the slope myself with a known weight (have a 20kg calibration weight for this) to confirm accuracy and therefore am confident that the data is correct across my units.

[Alex Simmons/RST]

People are confusing the term "calibration" when what they mean to say is "checking or setting or correcting the torque zero".

Calibration is a different function altogether. Testing torque zero is akin to ensuring a set of scales reads 0kg when there is no weight on them. Knowing that the torque zero is correctly set/measured is a necessary but insufficient test for a power meter's calibration. Like the bathroom scales, just because they read 0kg when there is no weight on them, does not mean they will read correctly when weight is applied. To know that, the scales need to be calibrated by comparing the reading with accurately known weights.

[softy]

People are confusing the term "calibration" when what they mean to say is "checking or setting or correcting the torque zero".

Calibration is a different function altogether. Testing torque zero is akin to ensuring a set of scales reads 0kg when there is no weight on them. Knowing that the torque zero is correctly set/measured is a necessary but insufficient test for a power meter's calibration. Like the bathroom scales, just because they read 0kg when there is no weight on them, does not mean they will read correctly when weight is applied. To know that, the scales need to be calibrated by comparing the reading with accurately known weights.

yes, absolutely true. but articles and manufactures refer to it as a "calibration". my point is why the need to zero every ride. it means the item is subject to influences and can't relate to where zero is.

Yes old scales were zeroed, but this more a case of parallax reading error or mechanical mechanisms not returning to exactly the same point. I have never had a electronic piece of equipment I have had to zero every operation in my testing history. Anyway a unit you don't need to zero is one less thing you don't have to forget.

[Alex Simmons/RST]

People are confusing the term "calibration" when what they mean to say is "checking or setting or correcting the torque zero".

Calibration is a different function altogether. Testing torque zero is akin to ensuring a set of scales reads 0kg when there is no weight on them. Knowing that the torque zero is correctly set/measured is a necessary but insufficient test for a power meter's calibration. Like the bathroom scales, just because they read 0kg when there is no weight on them, does not mean they will read correctly when weight is applied. To know that, the scales need to be calibrated by comparing the reading with accurately known weights.

yes, absolutely true. but articles and manufactures refer to it as a "calibration". my point is why the need to zero every ride. it means the item is subject to influences and can't relate to where zero is.

Yes old scales were zeroed, but this more a case of parallax reading error or mechanical mechanisms not returning to exactly the same point. I have never had a electronic piece of equipment I have had to zero every operation in my testing history. Anyway a unit you don't need to zero is one less thing you don't have to forget.

Yes, those writing about power meters in articles and marketing blurb should know better about the words they choose. It just ends up creating confusion when none need exist.

Parallax error aside, if mechanical scales don't return to zero after being stepped on, then that's either a form of zero drift or a form of hysteresis. That's quite a relevant thing to check for. It's been known that some power meters don't return to their previous zero point after a torque has been applied. That matters and is worth testing for.

Electronic bathroom scales are zeroed each time they are activated. That's why you are required to wait until the zero is showing on those scales before stepping onto them.

Checking and setting power meter torque zero is a normal thing for a strain gauge device that is operating in significantly variable environmental conditions and often with other equipment external to the meter that can influence the readings.

In the past decade, of all the innovations introduced to power meters not a single one has improved the accuracy of already existing devices and many models have sacrificed accuracy for some perceived convenience benefit. That's not a compromise I think is worth making.

[defy1]

So whats the consensus with regards to 4iiii not auto calibrating?

Say I am going for a 4 hour ride, if I start early in the morning, will finish afternoon and in Melbourne this can mean 10+ degrees variance in temperature. Does this mean to maintain accuracy and consistent power data for the whole ride I got to manually calibrate my PM at regular intervals during my ride?

[softy]

So whats the consensus with regards to 4iiii not auto calibrating?

Say I am going for a 4 hour ride, if I start early in the morning, will finish afternoon and in Melbourne this can mean 10+ degrees variance in temperature. Does this mean to maintain accuracy and consistent power data for the whole ride I got to manually calibrate my PM at regular intervals during my ride?

Possibly, who knows, and that is my point.

[panosk]

So whats the consensus with regards to 4iiii not auto calibrating?

Say I am going for a 4 hour ride, if I start early in the morning, will finish afternoon and in Melbourne this can mean 10+ degrees variance in temperature. Does this mean to maintain accuracy and consistent power data for the whole ride I got to manually calibrate my PM at regular intervals during my ride?

From their FAQ:
"The PRECISION strain gauges are sensitive to temperature, so we recommend that you start your ride with a 5 or 10 minute warm-up, and then zero your power meter. You shouldn’t have to do it again during your ride, unless you run into a major temperature fluctuation."

Additionally, power meter data are useful when you do specific training like intervals (short or long) or steady efforts and for pacing on a climb. In the case of a long ride that will have coffee and rest brakes, traffic lights, road crossings, chatting, power output doesn't really matter.

[defy1]

So whats the consensus with regards to 4iiii not auto calibrating?

Say I am going for a 4 hour ride, if I start early in the morning, will finish afternoon and in Melbourne this can mean 10+ degrees variance in temperature. Does this mean to maintain accuracy and consistent power data for the whole ride I got to manually calibrate my PM at regular intervals during my ride?

From their FAQ:
"The PRECISION strain gauges are sensitive to temperature, so we recommend that you start your ride with a 5 or 10 minute warm-up, and then zero your power meter. You shouldn’t have to do it again during your ride, unless you run into a major temperature fluctuation."

Additionally, power meter data are useful when you do specific training like intervals (short or long) or steady efforts and for pacing on a climb. In the case of a long ride that will have coffee and rest brakes, traffic lights, road crossings, chatting, power output doesn't really matter.

what is considered "major"?

Say on a 4 hour ride, I could be doing intervals in hour 1, and then in hour 4. If there is "major" temp fluctuations in between hour 1 and 4, and you don't calibrate, this would mean I couldn't compare hour 1 data vs hour 4 data. Correct?

[dalai47]

Just zero your power meter before the second set of intervals. It's not that hard...

[dalai47]

If that's already too much effort, how will you manage reviewing your data and setting your program???

[GTPilot]

If small percentage differences due to temperature fluctuation is a concern, then you are really not in the market for a sub $1k power meter. That being the case, it makes this conversation pointless.

[GTPilot]

Oh and FWIW I have not "zeroed" mine for over a month now riding in temps between 20°+ and 0°. Readings have not changed much.

[dalai47]

Not sure why you wouldn't zero your PM before each ride, or after 15 minutes into your ride if the bikes come out from a warm house?

[Alex Simmons/RST]

Oh and FWIW I have not "zeroed" mine for over a month now riding in temps between 20°+ and 0°. Readings have not changed much.

How do you know? Were you using a control to compare them with?

[GTPilot]

How do you know? Were you using a control to compare them with?

Yep

[panosk]

what is considered "major"?

Say on a 4 hour ride, I could be doing intervals in hour 1, and then in hour 4. If there is "major" temp fluctuations in between hour 1 and 4, and you don't calibrate, this would mean I couldn't compare hour 1 data vs hour 4 data. Correct?

About what is considered "major" you could send a email to their support to get their definition.

As for your example, personally, i would calibrate my power meter before each intervals section of my ride.
Even if 4iiii announces that there is no need to calibrate their power meter anymore, i would continue to do so.

[Alex Simmons/RST]

How do you know? Were you using a control to compare them with?

Yep

Can you describe the control?

[biker jk]

Ok, so I had my first proper ride with my 4iiii power meter today.

One issue is that when not pedaling, power (3 sec average) does not show zero until I pedal again. So it will show the power (3 sec average) I was doing before I stop pedaling then even if I don't pedal for 10 seconds it will not show zero power until I resume pedaling.

Also, I'm getting cadence from a Garmin combined speed/cadence sensor. I believe that the 4iiii also measures cadence but how do I display it on my bicycle computer. Do I need to reset my sensors to just take speed from my Garmin speed/cadence sensor and then my computer will obtain cadence from the 4iiii?

Finally, when I paired the 4iiii I had two power symbols, one Ant+ the other Bluetooth. Should I drop the Bluetooth version?

Thanks in advance for any help.

[panosk]

Ok, so I had my first proper ride with my 4iiii power meter today.

One issue is that when not pedaling, power (3 sec average) does not show zero until I pedal again. So it will show the power (3 sec average) I was doing before I stop pedaling then even if I don't pedal for 10 seconds it will not show zero power until I resume pedaling.

I had a similar problem with cadence. It didn't zero until 10s passed from the time i stopped pedaling. But it was a problem of my watch (suunto ambit) and not of the power meter, since my bike computer (garmin 510) showed the correct values. You should check it with a friends computer to see if the behaves the same.

Also, I'm getting cadence from a Garmin combined speed/cadence sensor. I believe that the 4iiii also measures cadence but how do I display it on my bicycle computer. Do I need to reset my sensors to just take speed from my Garmin speed/cadence sensor and then my computer will obtain cadence from the 4iiii?

Yes you must unpair the garmin sensor to get cadence from the power meter.

Finally, when I paired the 4iiii I had two power symbols, one Ant+ the other Bluetooth. Should I drop the Bluetooth version?

I suppose you have a garmin computer. Garmin's communicate with sensors through ant+. They use bluetooth to connect with
the phone and the mobile app. So you should activate bluetooth when you want to synchronize the computer with the app and garmin connect.

[biker jk]

Ok, so I had my first proper ride with my 4iiii power meter today.

One issue is that when not pedaling, power (3 sec average) does not show zero until I pedal again. So it will show the power (3 sec average) I was doing before I stop pedaling then even if I don't pedal for 10 seconds it will not show zero power until I resume pedaling.

I had a similar problem with cadence. It didn't zero until 10s passed from the time i stopped pedaling. But it was a problem of my watch (suunto ambit) and not of the power meter, since my bike computer (garmin 510) showed the correct values. You should check it with a friends computer to see if the behaves the same.

Also, I'm getting cadence from a Garmin combined speed/cadence sensor. I believe that the 4iiii also measures cadence but how do I display it on my bicycle computer. Do I need to reset my sensors to just take speed from my Garmin speed/cadence sensor and then my computer will obtain cadence from the 4iiii?

Yes you must unpair the garmin sensor to get cadence from the power meter.

Finally, when I paired the 4iiii I had two power symbols, one Ant+ the other Bluetooth. Should I drop the Bluetooth version?

I suppose you have a garmin computer. Garmin's communicate with sensors through ant+. They use bluetooth to connect with
the phone and the mobile app. So you should activate bluetooth when you want to synchronize the computer with the app and garmin connect.

I have a Wahoo Elemnt which can use both Ant+ and Bluetooth sensors.

I just managed to sort the problem out. I deleted the 4iiii Bluetooth sensor connection to the Wahoo Elemnt and kept the Ant+ connection and it's fixed the problem. So my computer now shows 0 power when not pedaling (after 3 sec of course).

I also removed the cadence magnet from my crank and my Wahoo Elemnt is getting cadence from the 4iii.

I'm loving the 4iiii.

[panosk]

I'm loving the 4iiii.

I'm loving the 4iiii too, for the last 1.5 year and about 800 hours of daily use and sometimes abuse!

[defy1]

I've had my 4iii for a few months now. I am happy with it and no problems.