Experiences with the electronic counter!

My experience with electronic counting has been positive. I obtained a Sigma Sport as soon as Neville posted his first results on its use, and I conducted a side-by-side comparison with a Jones/Oerth counter on a course measurement. I found that there was zero difference between counts obtained using the two methods. I later obtained a Protégé unit and found that it also worked.

A short article on the subject appeared in Measurement News, July 2004. You can download it from the RRTC web site at:

http://www.usatf.org/events/courses/certification/measurement_news/

The Sigma Sport has four magnets and a revolution is recorded every fourth encounter between magnet and sensor. The Protégé has one magnet, and records a revolution each time the magnet passes the sensor.

I found that I could not overcome the nagging feeling that the electronic counter method lacked robustness. Because a revolution is recorded each time the magnet passes the sensor, it is possible for extra revolutions to be recorded if the bike wheel moves backwards when the magnet is in proximity of the sensor. I have had this happen when wheeling over rough ground.

As each extra revolution adds about two meters to the measured distance, the error is not small. Moreover, if the Protégé is the unit used, there will be nothing to tell that the error has occurred. The Sigma Sport, using four magnets, will show the count increasing each time the wheel passes the zero mark. If it does not do this, it means that an error has occurred and that it would be a good idea to go back to the last reliable point and begin again. Checking the operation of the unit at each data-recording point is a good idea.

Since I now have one of each type (4 magnet and 1 magnet) I use them both. One checks against the other. In this way I am able to be aware if something is off. If I had only one, I would choose to use the Sigma Sport, as it will show a difference when the zero point is reached.

The Jones/Oerth counter has no potential for uncertainty, unless it is broken.

As a measurer I believe that I can use the units properly, and I can prepare paperwork that another certifier can understand. As a certifier, I am not sure how I would handle an electronic submission unless it carried with it credible evidence that revolutions were reliably counted.

Overall I like using the electronic counter. It is nice being able to reset between intervals, although it does pose new requirements in data-presentation. The indicated revolutions change slowly and give me plenty of notice when I am coming up on a place where I must stop and make a mark or otherwise take data.

The electronic method can be as accurate as the Jones/Oerth, but care must be taken to assure that revolutions are being properly recorded. If the electronic method is to be used, it is a good idea for the user to consult with other users before plunging ahead.

I would be very interested in hearing from anyone who is using the electronic counter. Many have obtained them over the last few years, but as far as I know only Pete besides myself has been daring enough to actually certify a course with one.

It is true that using the four-magnet technique, if a measurer rolls back a magnet through the sensor, then this is immediately evident through the generation of at least one spurious impulse and destruction of the synchronization of the meter zero with that of the wheel rim zero. (This check does not work if the total number of spurious impulses is a multiple of four.) On the other hand, the chance of creating spurious impulses is four times more likely than with the one-magnet technique. One must not forget though that the Protégé can also be used with the four-magnet technique simply by setting the circumference to 2500 mm. In fact, Pete I recommend you do so with your Protégé and use the same four magnets as you are using for the Sigma.

With the one-magnet technique, to avoid spurious impulses the measurer should get used to glancing at the bottom of the wheel as he stops to avoid stopping on the zero mark. While walking a bike through curbs or ruts, he should keep his eye on the meter as the wheel goes through the rim zero. Should spurious impulses occur though inattention and bad luck on one ride, this will be very obvious by the fact that the other ride will go about one or two revolutions more. I like to do at least one ride of the course without stopping and with no possibility of spurious impulses.

Just as with many other things in certification, a certifier has to trust that the measurer is operating the electronic counter correctly. A measurer can gain this trust by running the Jones simultaneously for a few measurements and or by the reproducibility of his results.

One advantage of the Jones counter and its non-instant-zero feature/bug, is that it essentially makes the second ride a blind operation. Especially on a metric course, on the second ride I have no idea what the count should be at each of the mile marks.
While knowing where one stands at each mile mark compared to the first ride might provide a bit of reassurance to the measurer, it increases the possibility of subconscious corrective adjustments being made during the ride.

Mark:
If you like the non-zeroing feature on the Jones, there is nothing to stop you using it on an electronic counter!

Checking my status each mile would be too tempting! :-)

I will eventually get my protege working correctly and try it out. Haven't had time lately.
Just wanted to point out that despite all the things we will gain, there will be a couple things we will lose, after we all go electronic.

I have read with interest a lot of the material on electronic counters on this forum, but I still have one concern that does not seem to have been addressed. I find with my electronic counters that if I roll the bike forward slowly, so that the speed of the magnet passing the pick-up is low, the counter does not register the movement. One of my odometers has a 3 decimal place resolution (ie to 1 m) so it is easy to verify that counts are not being recorded.

Has someone tested the Protege and the Sigma units to verify that they are accurate even when the bike is moved very slowly?

Paul:
Please read "END OF THE ELECTRONIC ERA?" posted April 05 in this section.

Since I wrote the above, I have tested the wired version of the model you refer to (dB4L), and found that it is the one exception to the rule that all wired models have low-speed response. I managed to get it to work, but only with a very critical operational procedure that few measurers would ever consider using.

Incidently I am now recommending both the Protege and the Bell ($7 from Walmart).