hac4 not reliable

Andrew Smit said:

I have been using a HAC4 computer for sometime now.

The heart rate readings are unreliable on descents or when riding at
high speed when the HAC4 is mounted on the handlebar mount.

Has anyone else had similar issues ?

I've never found a pulse monitor that didn't have such problems from
time to time. I have two Polar pulse monitors, two Cateye speedos with
pulse monitors, and a HAC4. They all give invalid readings at times, the
HAC4 being no worse than the others. Windy conditions and synthetic
clothing, particularly polyester, seem to make the problem worse. I find
they all work much better if I smear sorbolene on the chest belt's
contact strips before putting it on. If I don't do that I frequently get
no readings at all until I've been riding pretty hard for 30 or 40
minutes.

Low batteries will also exacerbate the problem.

Nick

"Andrew Smit" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I have been using a HAC4 computer for sometime now.

The heart rate readings are unreliable on descents or when riding at
high speed when the HAC4 is mounted on the handlebar mount.

I have tried everything I can think of to fix this:
[snip]

I've never found a pulse monitor that didn't have such problems from time to
time. I have two Polar pulse monitors, two Cateye speedos with pulse
monitors, and a HAC4. They all give invalid readings at times, the HAC4
being no worse than the others. Windy conditions and synthetic clothing,
particularly polyester, seem to make the problem worse. I find they all work
much better if I smear sorbolene on the chest belt's contact strips before
putting it on. If I don't do that I frequently get no readings at all until
I've been riding pretty hard for 30 or 40 minutes.

Low batteries will also exacerbate the problem.

Nick

(Andrew Smit) said:

I have been using a HAC4 computer for sometime now.

The heart rate readings are unreliable on descents or when riding at
high speed when the HAC4 is mounted on the handlebar mount.

Have you used other heart rate monitors under identical conditions
(same speed, same route, same clothing, etc.) without any problems?
Does the HAC4 work reliably when not on the handlebar mount?

Do you wear a loose-fitting jersey? Clothing flapping against the
chest strap can interfere with heart rate monitors.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/

On 22 Jul 2004 21:05:11 -0700, [email hidden] (Andrew

Smit) said:

I have been using a HAC4 computer for sometime now.

Quoted message said:

The heart rate readings are unreliable on descents or when riding at
high speed when the HAC4 is mounted on the handlebar mount.

I had a similar problem with a Vetta unit. Finally figured out that
the battery was bouncing inside the compartment, creating false
impulses and screwing up both speed and hr readouts. I opened the
compartment and adjusted the spring contact for a tighter fit,
and--voila!--problem solved. If the HAC has a replaceable battery in
the chest strap, you might check that too.

Let us know if and how you get it fixed, please. Curious minds want to
know......

Nick Payne said:

HAC4 being no worse than the others. Windy conditions and synthetic
clothing, particularly polyester, seem to make the problem worse.

Triboelectrification.

I.e., static discharge.

Any two dissimilar materials can have dissimilar ionization
energies and create a work-function that transfers
electrons from one to the other simply through contact.
More contact with fresh, uncharged material A yields higher
charge on material B. It can affect RF operation. I used
to have fun driving my car on the painted lines on certain
roads while listening to weak AM stations, because I could
hear on the radio when my tire had contacted the paint.

With charge comes potential, and with potential comes
corona discharge.

I can see the wind charging up a polyester jersey pretty good.

Did you say you were wearing a hunk of metal connected to
your body via an electrolytic solution? Sounds like a nice
sink for a corona discharge to me.

And did you say that hunk of metal was the antenna for the
low-power transmitter stationed within its core?

Solution: ride naked.

--Blair
"The FCC ain't gonna help you now."

I had the same problem, and I called Veltec sports (the US importer), and
they suggested wearing the chest strap a little lower on the chest. I was
having problems when I was out of the saddle, and this put the transmitter
slightly closer to the receiver.

Also, keep in mind that the HAC 4 takes readings only every 20 seconds (the
HAC4 is programmed to collect a very large number of statistics over 64
hours, which limits the frequency of data collection), while the default
setting for the best Polar is to take a reading every 5 seconds. So if you
have a problem, it will appear to be worse with the HAC4. I have worn both
on a long ride, and in the end they both give me the same readings, however
there were plenty of times during the ride where the HAC 4 gave me a zero
reading while the Polar gave me an accurate reading.

"Andrew Smit" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I have been using a HAC4 computer for sometime now.

The heart rate readings are unreliable on descents or when riding at
high speed when the HAC4 is mounted on the handlebar mount.

I have tried everything I can think of to fix this:

- replaced all batteries
- moved the fork mounted transmitter high up the fork (not sure why
this would fix HR reading but thought I would try it anyway)
- used electode gel on the chest transmiter to improve signal
- tried a polar chest transmitter
- Tried riding without cell phone/blackberry on the theory that other
signals are interfering with the HR signals
- Removed wheel magnet from my Campy ergobrain (again, on theory that
other signals are somehow interfering with HR signals)

For an expensive item, this is pretty poor - one of the major
functions (of the 57 it boasts) is simply useless.

Emails to US and German suppliers have received no response.

Has anyone else had similar issues ?

Thanks