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One final comment on accuracy. They are extremely accurate. The pulses 
are received by the watch. The watch uses a crystal time standard 
(quartz) to calculate the time between beats and then uses that the 
calculate the heart rate. The accuracy is as good as that of the quartz 
crystal - which is quite accurate (much more than a human watching a 
watch).

It's not the accuracy that is the question but the artifacts generated.

Truman

Truman Prevatt wrote:

> When it is showing a "double beat" it is actually all the beats - if 
> you listen closely in a stethoscope you will hear the four parts of 
> the beat. The HRM is designed to only count two - on the assumption 
> that the current flow from the other two parts of the beat are too 
> small to be detected by the sensors. This is true in humans and these 
> units are modified from those designed for humans. If the current flow 
> associated with all four parts of the bear are strong enough to 
> trigger the sensor - you get double the heart rate.
>
> I've taken a lot of pulses at rides and have seen it a couple of 
> times. Interestingly enough it has always been on non-Arabs, both 
> Morgans and walking horses. One time a walking horse comes in. He was 
> calm, alert looked in great shape but his heart rate read 110 off the 
> monitor. I put a stethoscope on him and the 110 had to be 55 since by 
> the time I got a count on the stethoscope it was 52.
>
> My old walking horse mare had a strong heart beat and my monitor would 
> pick up all four parts of the beat.
> You can usually eliminate this with your own monitor by placement of 
> the electrodes or changing the polarity of the connection of the 
> electrodes to the transmitter.  The transmitters have a positive (red) 
> side and an ground (black side). The connectors one the transmitter 
> normally reflect this. Sometimes by reversing the which electrode goes 
> to which connectors will solve the problem.
>
> With my mare I solved it by switching the girth electrode to her right 
> side and the under saddle electrode to the left side (opposite of the 
> recommended position). That solved the problem. If I rode with both 
> electrodes under the saddle it also solved it.
>
> More horses - but not many - have the opposite problem. The hand helds 
> can't detect the heart beat. That can be an issue more it seems on 
> slab sided horses. You can normally solve that by holding the hand 
> held monitor lower than you normally would. I've won quite a few bets 
> when people walk into the box, I put it on and they start tell me you 
> have to use a stethoscope on this horse, yadyad......... By the time 
> the third yada comes out - I have the pulse, call their number and 
> send them on :-) .
>
> Truman


>


--

"A mathematician is a device for turning coffee into theorems."

- Paul Erdos (1913-1996)




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