Polar HR S720i Speed Sensor Problem

Mike Prendergast said:

Does anyone have any ideas on what is causing this? The unit is new. The speed sensor and magnet
are very close (~1-2 mm). And as I noted the speed indication works fine while I'm sitting down.

You can up the power of the transmitter in the speed sensor. Do a Google search and you will find
detailed instructions on how to do it, or take it to your nearest Polar Service Center. They'll most
likely do it for free.

--
Perre

You have to be smarter than a robot to reply.

Quoted message said:

The speed indication works while I'm sitting on the saddle. But as soon as I stand up and pedal or
coast off the saddle the speed reading goes to zero for a few seconds or until a few seconds after
I sit back down. During a 96 mile ride, the dropouts caused my mileage reading to be 85 miles.

Does anyone have any ideas on what is causing this? The unit is new. The speed sensor and magnet
are very close (~1-2 mm). And as I noted the speed indication works fine while I'm sitting down.

Mike,

I'd do this:

1) put the HR transmitter somewhere close to the unit, so it's position doesn't change when
you stand.

-If the problem still occurs, your standing and the resultant flex probably is it. Possibly the bar
and stem flex moves it just out of range.

-If the problem goes away, it's probably a case of the HR signal processing causing a speed
sensor signal lock problem. As if a little extra power is needed to receive and process the HR
signal as your chest moves a bit further away, which reduces the detection of the speed signal
just enough to lose it. Nasty problem in this case since you are close to the rated range limit
for the speed sensor.

In either case, stronger batteries, or a boost in the speed transmitter power as the other post
noted, may solve it.

Be sure to post your solution here to archive for future users.

Doug

Doug said:

Quoted message said:

The speed indication works while I'm sitting on the saddle. But as soon as I stand up and pedal or
coast off the saddle the speed reading goes to zero for a few seconds or until a few seconds after
I sit back down. During a 96 mile ride, the dropouts caused my mileage reading to be 85 miles.

Does anyone have any ideas on what is causing this? The unit is new. The speed sensor and magnet
are very close (~1-2 mm). And as I noted the speed indication works fine while I'm sitting down.

Mike,

I'd do this:

1) put the HR transmitter somewhere close to the unit, so it's position doesn't change when you
stand.

-If the problem still occurs, your standing and the resultant flex probably is it. Possibly the
bar and stem flex moves it just out of range.

-If the problem goes away, it's probably a case of the HR signal processing causing a speed
sensor signal lock problem. As if a little extra power is needed to receive and process the HR
signal as your chest moves a bit further away, which reduces the detection of the speed signal
just enough to lose it. Nasty problem in this case since you are close to the rated range limit
for the speed sensor.

In either case, stronger batteries, or a boost in the speed transmitter power as the other post
noted, may solve it.

Be sure to post your solution here to archive for future users.

Doug

By changing the recording rate from every 5 to every 15 seconds I was able to reduce spurious speed
as well as cadence readings to essentially none. Best, Jeff
--
remove sixes to reply

Doug said:

In either case, stronger batteries, or a boost in the speed transmitter power as the other post
noted, may solve it.

I had the same problem when I first installed the wheel sensor for my 710. Even with the power
cranked up to maximum, operation was 'iffy' at best.

Quoted message said:

Be sure to post your solution here to archive for future users.

Google already has my fix listed. Twice, the first time, and the second time before another poster
knew google existed.

google.comgoogle.comOpen ↗ click on the groups tab, in the search box, type in:

Polar speed sensor antenna.

And yes, it's STILL working pefectly, only my HR transmitter is having dramas
when in vincinity of power lines or in close proximity of other HR transmitters.

--
Linux Registered User # 302622 <counter.li.orgcounter.li.orgOpen ↗

In article <[email hidden]>,

Per Elmsäter said:

Mike Prendergast said:

Does anyone have any ideas on what is causing this? The unit is new. The speed sensor and magnet
are very close (~1-2 mm). And as I noted the speed indication works fine while I'm sitting down.

You can up the power of the transmitter in the speed sensor. Do a Google search and you will find
detailed instructions on how to do it, or take it to your nearest Polar Service Center. They'll
most likely do it for free.

I've had my speed sensor attached to my rear wheel for over a year without any problems
whatsoever...I did do the high power mod.

basically take the speed sensor apart and switch the jumper from the inner two wires to the outer
two (there are three) and you're done.

________________________________

Remove S.P.A.M in email adddress Climb <at> mac <dot> com
________________________________

Quoted message said:

Quoted message said:

In either case, stronger batteries, or a boost in the speed transmitter power as the other post
noted, may solve it.

By changing the recording rate from every 5 to every 15 seconds I was able to reduce spurious speed
as well as cadence readings to essentially none.

Jeff,

That's a weird one. The recording rate on these Polars does what exactly? Determine how often data
is saved for you to analyze later?

If so, it may indicate some sort of power drain in the receiver. Meaning, as the receiver is writing
data to memory, at those moments it becomes slightly less sensitive to the sensor's signal. Combined
with standing, when the HR signal processing may require more power, could lead to all these probs.
Many possibilities.

It reminds me why I like two things: 1, wired sensors; 2, separate HRM and cyclo comps. Actually, #2
since I use the HRM for other exercising and am too cheap to have more than one HRM.

Doug

Thanks for all the feedback on my speed sensor problem.

I did look up how to boost the power level of the speed sensor and also received instructions from
Polar on how to do it. While waiting for the replies to come in, I moved the sensor up slightly (<1
cm) so that it is now just under the front brake pad. This was enough to change the reception and my
dropout problem has stopped. I've ridden many miles (about 900) with the sensor placed a little
higher on the fork and have no dropouts of speed reading while standing or any other data dropouts.

Mike Prendergast