Ridecamp: [RC] hrm fyi hlep

FROM   Roger Rittenhouse     roger@xxxxxxxxxxx
Guess i should write up the faq on my web page?

First Cindi hit is about right on -

The problems with funky readings:

1 DRY horse - USE electrical conductive gel - NOT KY - use ALOE gel or
EKG gel or SALT WATER?  Dont wait for him to sweat - wont work well
most of the time.
IN a VC after you washed ALL the salt off the horse, washed the girth
and the horse fails to sweat LOTS after 50 miles, you NEED some gel or
add salt back to the girth. We must obtain a solid ELECTRICAL
connection to the horse, with a conductive medium.

2. LOOSE GIRTH.. oh well cant fix that one  -(SOLID connection - NO
movement of electrode against the horse.

3. LONG HAIR   cut hair spots  holes  that is not shaved
4. NEOPRENE   use fussy girth  - or glue the Velcro on the girth, use
a few turns of vet warp over the top of the electrode to fix it to the
girth and hold sweat.

5. ELECTRODE PLACEMENT. MANY do this 'wrong;  ( note - remember I have
developed this and been doing this longer then any others 'selling'
hrms - for horses.   but hey  HOW difficult is it figure this out??

    1. TOP lead  should be 24 inch long  to go WAY under the saddle pad
 UNDER the spot where the stirrup hangers and billets are located
..NOT in front of the wither or in the pocket behind the wither but in
the small of the back UNDER YOUR seat. (no motion)
    2. BOTTOM - variable- NORMAL place  at the point of the elbow-
where you take the pulse BUT ON the RIGHT side, (no lead to hang up
on the girth )  NEXT place -  on the LEFT side at elbow.
  ON SLAB sided horses  - place LOWER to the rounder section of the
chest on the barrel - OR even dead center.

( to make our long coil lead LONGER- just pull it apart and stretch it
- will go 5 feet long)

   DONOT place the BOTTOM electrode on the SIDE - the girth will bunch
slide pucker etc and move the electrode all over the place, thus bad
readings.


TEST TO SEE IF YOUR READING IS VALID
1. get going, at a working level  with a wet horse or gel on a dry one
2. pick a speed settle in at a solid HR.
3, press on the go button a bit - HR increase a few beats like 5 ?
4, apply the brakes a bit HR go down?
DOES THE READING TRACK YOUR SPEED? slight changes  in effort will be
noted.

Stuck reading or reading that are wrong for the  normal
 effort - running up  hill at 90- walking at 185 ...

TECHNICAL DISCUSSION OF HOW THESE WORK

The EKG pulse is picked up by the conductive electrodes- the pulse is
sent to the transmitter by the leads, thus the leads and the electrodes
MUST be low resistance and not induce any noise or static.

The transmitter looks for these pulses. the transmitter will emit a
RF burst (51khz) when the R wave of the QRS EKG exceeds a fixed level.
This is to prevent small spikes and noise from triggering the
transmitter. Once the transmitter fires, it shuts off until the post T
wave of the EKG is passed. MOST of the time the T wave is of a lower
voltage value to not trigger the transmitter - however SOME horses EKG
will double fire the transmitter. This is noted on the REC watch by
the heart icon blinking TWO times for each pulse
FIX- reverse leads wires.
NOTE it is NOT REALLY necessary to hook the leads to the transmitter
based on any 'snap' color. We did write directions to cover that since
the transmitters we used were color coded. Our new models are solid
block with no snaps on rubber flex  ends to go bad.. It does not matter how
you connect. If you cant get good readings one way, just reverse the
leads.
So now we have the transmitter sending out a burst of RF for every
beat of the heart. AND maybe a few false bursts.
WE use the RECEIVER watch to detect and count these bursts and then to
add them up  -compare to time and display a beat per minute value.

 DISPLAY

The rec watch consists of  a time clock and computer and memory.
Works as such:  a sample window opens - counts the transmitter pulses closes and displays the HR.
IF during this read window the electrode moves around - (carbon silicon
rubber) a false spike is sent to the transmitter, if the spike is
large enough the transmitter will fire and put out a signal - the
receiver will try to count this as 'real' beat. This is called artifact.

The computer in the receiver does not filter out this false signal.
WHY - because ALL the monitors on the market today - including the new
one from P.... ALL-  are made using HUMAN HRM components.
The design ASSUMES the CHESTBELT transmitter will be snugly strapped to the HUMAN
chest. THUS no motion induced false signals. The mfgr of the human
setup  provides information sheet advise to  this effect , solution tighten the
belt.
Some of the assorted models from other mfgrs have a very slow update
window, as in 5 to 8 seconds.
None of the EHRM will filter this false signal out.
The last and very costly EQUINE HRM was from EQB called EQUISTAT.(1985
to 1990) That monitor tried to filter out artifact but also did a  20SEC overall
average thus you got a  flatter looking hr, missed the highs and lows.
It was the ONLY HRM designed for use with EQUINE.
ALL 'horse ' HRM since then use the HUMAN components with adapted lead
s and transmitter  and place in boxes with a HORSE on the front.

Two ways to correct the error. Tighten the electrodes on the back and girth of the
horse - means SUNG girth. Place electrodes in less motion location -
under saddle.
Number 2 is to GLUE on the electrodes. We did that 12 years ago. The
riders will not use this method nor would I - the RIDER DESIGNER.
So we elected to use MOVEABLE PICKUP  electrodes as well as the other
mrgr at the time.( There were only 2 me and Bob Walz)

Next option, to use a receiving device with a SHORTER sample window,
say 2 seconds. The component I have selected and  adapted use a 2 second sample
count window.  So the probability of 'seeing' a false pulse in 2 seconds
is much less then in 5 to 8 ???

The logic is - count for the sample window time, display pulse AFTER the
buffer stack is full - ( 6 spots) takes 12 seconds to obtain a valid
pulse value. The displayed HR is a rolling 12 sec average of the HR.
With a new value (count of pulses) every 2 seconds
Works on FIFO
IF pulse signals are erratic the counts cannot be made - the rec will
drop that sample and displays LAST know good pulse. UNTIL ALL values
in the memory are 'defective' then it gives you 0 ZERO.

So the smaller the sample window the chances of a valid good REAL
reading are improved. We still have motion and dry electrode artifact
but YOU dont know that.   Well, now you do.

I have one model from Acumen that does it different then any HRM out
there - it reads for 5 or 6 BEATs and  measures the TIME then displays
the HR. This model is very susceptible to small changes in effort.
It does appear to do OK with artifact but I get some wild readings
when the electrodes are not correct.

The component mfgr with the shorter 2 second sample window are Cardiosport and Sensor Dynamics.


So there you have the practical and a little techie explanation of the
 how why and use of these neat little tools.

Hope this helped to explain a few of the issues and common
misconceptions.

Guess I will save this write up and add it to my web page.

and I will close out with the commercial in the sig line

No, I did not go to a ride this weekend  BUT we rode for an HOUR
yesterday.

Roger Rittenhouse
Equine Performance Technology
V-MAX Equine HRM Systems
www.vmaxept.com
800 655 8629


ps I read this over 4 times - I am sure there are a few errors, so
deal with them.. go ride

Roger Rittenhouse



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