jberenyi

I have a Polar CS200CAD cycling computer and for some reason after our group ride it was 11% low on mileage. Speed is accurate but its the mileage that is low. Our ride today was 55 miles and we've been doing it for 3 years. But my computer said 47.6 miles. I've checked my wheel length setting and it was correct (2102mm).

My first question is, do computers still register mileage even though they may go into pause mode. I would think they don't because if time stops doesn't the mileage too? Even if this was the case I would have to pause for almost 7 miles. Anyone know what could be the cause?

khuon

Some computers have a bit of hysteresis (sometimes it's artifically preset). This can throw off your mileage reports over time. However, a bigger source of error probably has to do with calibration differences. The question is, how do you know the route is exactly 55 miles? Which one is correct? Or is both the computer and the other instrument used to measure the mileage wrong?

slowandsteady

Do you have a HRM? This can cause some interference and if it interfered for long enough, you will be short on mileage.

spdrcr5

The Polar CS200CAD is a combination HRM/Cyclocomputer so there wouldn't be any interference since it is an all-in-one device.

I would try the computer on another bike and calibrate it for that and then ride over a known distance. Or add on a second computer to your bike and compare the two after first recalibrating your Polar CS200CAD, reset it to factory defaults if need be. If the Polar is still off then contact Polar and ask for it to be looked at.

byte_speed

Is that a wired or wireless computer?

Either way, to be off by that much I would suspect a
connection or reception/interference problem. Do
you watch it pretty closely? Could it be registering
0 for the 20 min or so it would take to cover 7 mi.?

jberenyi

Yes I watch it closely. Other than the ocassional pause modes it goes into due to interference and such like other computers it acts normally. So I take it that when computers go into pause mode it is not registering mileage even though you are moving?

gwhunt23

Go to a local high school or something and ride your bike around the track. See if you get 400 meters (0.2485 miles).

rodrigaj

I have a polar 720i.

There is no auto pause mode. It stops when you stop, starts when you start. Interference after passing electrical generating sub stations is normal but highly unlikely.

One very frustrating thing about the 720i was that it was extremely sensitive to handlebar placement. Make sure the speed sensor is on the same side as the computer and experiment with the computer placement. I finally found a spot that will never lose the signal from the speed sensor. I had to move the computer in 1cm increments from the stem toward the drops and go on 20 mile rides. I found a location that just allows me to put my hand on the upper bar before the turn toward the brifter begins.

Once I found the "sweet spot" all interference problems went away. I really think that polar speed sensors need further refinement. They should not be that tempermental. No other wireless computer I used was that touchy, but I wanted all the functions on one computer. Surprizingly, the cadence sensor is not sensitive at all. It has worked flawlessly regardless of the computer placement.

Good luck. It took me a while to figure this out. Contacting polar yielded standard precautions which are already stated in the user manual. They really did not help at all.

Cleave

Hi,

+1. With any of the non-GPS computers (wired or wireless), if you want precise mileage, then you need to calibrate the computer for your wheel size every time you change brands or model of tire or tire pressure. The rolling radius setting has the largest impact on mileage precision.

jberenyi

On the Polar CS200CAD if you encounter interference it will enter Pause Mode. Again, does this mean that even though I am moving, the computer will not register in a buffer of some sort or do I lose mileage from the time it entered Pause Mode to the time it started?

Oh yeah, and I agree with another member that Polar needs to refine their transmitters. Even though they are coded, they still get their fare share of interference from who knows what. Too bad their isn't competition for them in this price package and feature offering. Polar are you listening???

crypticlineage

My computer regularly spits out a little more mileage than what routeslip says. For example my last metric century was:

routeslip: 61.8 miles
sigmasport BC800: 63.88 miles.

This difference became noticeable after I switched from big knobby 2.0" tires to 1.25" thin tires. I am not sure if thats the cause because the rim dia should still be 26", shoudn't it?

khuon

Actual tyre diameter is what matters and this can change depending on the tyre. You need to calibrate doing a rollout using you and the bike set up for actual riding. Do three or more rollouts with the bike weighted (by you) and then average across them.

Stacy

I have the CS100 with the optional Cadence module and I've never noticed it go into "Pause Mode" when I encounter electronic interference. More likely I'll get some momentary aberrant reading, like my heart rate will go from 60 to 230, and then the computer will return to it's normal readings. That doesn't seem to effect my speed or mileage - just the maximum heart rate recorded for that ride.

If it's frequently pausing more likely it's what rodrigaj suggested - some kind of physical interference between the speed sensor and the computer. Make sure you have a clear, visual line of sight, between the cyclocomputer and the speed module.

jberenyi

Right now the computer is mounted on the stem and its less than the max distance allowed per the Polar manual. That's odd that when you encounter interference that your unit does not go into a pause mode until accpetable communication begins. I thought all computers did this.

Retro Grouch 

You should probably roll out your tire to measure an accurate circumference. The diameter of the rim doesn't matter. What matters is the circumference of the tire. Tires have a roughly circular section so a wider tire is generally a little taller too.

Stacy

In order to get mine to work I had to mount the cyclocomputer on the right side of my handlebar with the speed sensor turned towards the rear on the right fork. When I had the sensor on the front of the fork commiunication seemed to be blocked by my front brake. Ironically I have the cadence module mounted on the left side of the downtube but there's no problem there. All I can guess is that the cadence module has a wider beam than the speed sensor.

The problem seems to be more like the computer doesn't recognize interference as "unacceptabe data" so it just factors it in and skews legitimate data. Maybe the CS200 deals with this differently since it's a step up from the CS100 but... unless you're actually seeing data that's totally outside the norm this pausing sounds more like it's caused by lack of communication between componants than outside interference.

khuon

Exactly. There's a difference between interference and false signals. This is what happens when you ride over a traffic sensor which is essentially a metal detector that operates by inducing a magnetic field through a pulsing EM field. This kind of thing will trip the speed sensor as if the wheel magnet were passing by it. The result can be something like this recorded max speed.

jberenyi

Thanks for everyone's input. I re-checked my distance to center of sensor and it is right at 1' 6". This is max for the manual. However, I did disengage the computer from the mount while running the front wheel at about 10MPH and I could add another foot before it did not read anymore. So I guess the distance is okay. I like the idea of turning the sensor around though. For now I'm going to try getting the sensor closer to the computer but I can only move it another 2-3". I did send Polar an email on this issue. We'll see what they say (yeah right).

One other oddity I failed to mention about this computer is that it occasionally gives false %Max readouts. Anywhere from 112%-120%. It only does this in % Max mode not HR mode.

Stacy

Did you enter your Maximum Heart Rate manually or did you let the cyclocomputer estimate it? Anything over 100% indicates you reached a heart rate that's higher than the MHR that's been set in user preferences.

I've noticed interference from two locations that I pass regularly. One is an unkonwn source but the other is a heliport next to the bikeway. Larger helicopters taking off or landing sometimes send my recorded heart rate through the roof.

jberenyi

Just got back from the High School Track. I set the CS200 to metric and went once around in my lane. As I went over the line it said .4 KM. I had to make sure it tripped right at the line because the CS200 only have a one place decimal ie x.x. I miss the two place on my old Ciclosport. Anyhow now I am totally confused how I ended up so low on yesterday's ride (about 7 miles).

Cleave

Hi,

If you are going to try to see if the odometer is calibrated by riding around a running track you need to ride say 10 or more laps. That way you will be able to "see" the decimal error, if one exists.

Also, I haven't seen where you've written anything about how you are calibrating the computer to your wheel size. Are you rolling out the wheel and measuring the distance and putting that into the computer's calibration equation? Or are you using the "standard" setting for your tire size? Again, whell calibration has a big effect on the precision of the computer.

BTW, I used a Polar computer for 4 years and although it had its problems with interference, it was fairly precise -- even when I rode past powerplants which would cause my speed to jump to 60+ MPH -- I wish!

jberenyi

Yes I calibrated the unit using the roll out method. I did it three times and took an average. Originally I had set the computer to 2112mm but I had to re-set it to 2108mm. All that did was decrease the preceived distance by lowering it. I was hoping it was the other way. I'm going to do the track thing again and go around several times as you suggested. I only wish this darn computer had two place decimals.

cyclintom

Do you suppose that anyone stopped to think about the problem?

The computer was measuring SHORT. Interference or false signals could only INCREASE the mileage.

The only thing that can be wrong is that the jberenyi has the calibration incorrect.

jberenyi

I beg to differ. 4mm difference does not account for 7 miles off on a 45 mile ride.

rule

jb...I had the same unit, basically doing the exact same thing. Most of my issues boiled down to data drop-outs and pauses due to interference from external sources along my ride, but I never could solve the problem.

After about a year of doing all the stuff that everyone is describing I was told by the good folks at Polar that older CS200CAD units were prone to these issues, mostly due to sensitivity of the receivers to interference, that some of the newer units will do it too and that if you got one of the bum units (new or old) you would definitely know it. I confirmed this with the authorized Polar dealer from whom I had purchased the unit. They basically said, "Yeah, they can do that. We had that issue a lot when these first came out." They refused to work with me and instead kicked me back to dealing with Polar on any warranty issues. Polar basically told me that their units could be susceptible to interference and it couldn't necessarily be helped.

So here's how I fixed the problem. I bought a new CS200 unit from the same dealer where I got the original. I took out the new CPU, calibrated it and put it on my bike. I put the old CPU in the box and returned it to the store for a full refund. I get no drop-outs, pauses, or psychotic HR spikes with the new unit, and Polar and their authorized dealer get to make good on replacing a bum unit on their nickel instead of on mine.

YMMV.