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View Full Version : Summary:EMG+Kistler+200Hz cameras



Stacpoole Podiatry
09-03-1997, 05:36 PM
Thank you to all that responded to my request, it is much appreciated.

Cheers,

Susan :-)


The original request:

Hello All,

I would like your advice about synchronising an EMG, a Kister force plate
and 2 200Hz cameras(VHS PAL type made by Peak). We presently have a system
that links all these with 50Hz cameras, using a light for the camera sync,
but at 200Hz the light is not suitable. I have searched the BIOMCH-L
archives but to no avail.

I thank you all in advance for consideration of my problem and I will post
a summary of the information that I receive.

Cheers from sunny Ballarat, Victoria, Australia

Susan

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Susan Stacpoole-Shea
Injury Prevention and Control Research Group,

PhD candidate, University of Ballarat,
School of Human Movement and Sport Sciences,

309 Eyre Street, Ballarat, Victoria, Australia
Mobile phone; (015) 861 591
Home phone/fax; 03 53 314440
Email; spod@netconnect.com.au

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From: Young-tae Lim
To: Stacpoole Podiatry
Subject: Re: EMG+Kistler+200Hz cameras
Date: Wednesday, 27 August 1997 12:40

Hi! Susan,
Check the PEAK synchronization unit.
I think you can buy this unit from PEAK company.

Young-tae Lim
Biomechanics Lab.
Dept of Kinesiology
University of Illinois

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Susan, we used to use a similar system to the one I imagine you are
currently using. We tired of the cabling problems we kept getting, so we
simplified the cabling, and integrated the video sync. pulse into the left
hand edge of the video image itself (as a white box). The added spin off of
this is that we use the same system to put another 15 marks which we can
use for other inputs such as foot switches etc. down the left side of the
screen (an area of the video signal which is most prone to distortion due
to the optics of the video system, and thus not particularly useful for
video measurements). Since the cameras are genlocked, the electronics was
substantially simplified.

The upshot of all this was one multi core cable per camera, and video sync.
in the video image ready to be digitized using the PEAK program.

There is a little information on our web page (a very little!) :
http://www.health.latrobe.edu.au/hs/ss/TS/projects/projects1.html

Feel free to phone me...


Cameron D. Grant

```
\|/ (o o)
`o0____________________________--+----o0o----+--______oOO__(_)__OOo________0
o'
|Cameron D. Grant | Ph. : (03)9479 5637
|
|Technical Services Unit |
|
|Faculty of Health Sciences, | |
|NW10, | |
|Latrobe University |
|
|Bundoora 3083 | email :
C.Grant@LATROBE.EDU.AU|
,o0____________________________--+----o0o----+--___________________________0
o.
/|\

http://www.health.latrobe.edu.au/hs/ss/TS/TSUhome.html


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VIDERESENDT MELDING fra Stacpoole Podiatry (SPOD @ SMTP
{spod@netconnect.com.au}) .. 27.08.97 02:58
*** NOTAT fra BJxRG FALLANG (BJORGF @ P56FRIGG) tid: 27.08.97 08:47
We have the same system from Peak, and are able to sync the system either
via vertical force channel in the forceplate automatically at contact or
manually through the EVC Unit. Are you sure Peak can't help you with this?
Bjorg

Bjorg Fallang M.PT
Oslo College, Faculty of Health Sciences, Physiotherapy
Pilestredet 56
0167 Oslo, Norway
Ph.:47 22 452512, Fax: 47 22 452505



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hmmm. does your camera provide HSynch, VSynch, or a GenLock (eg,
linelock) output signal(s)? If so, you could use these signals to
trigger synchronization of your various devices precisely to the video
recorded from your cameras.

I pressume that at least one of the cameras acts as the 'master' or there
is some 'master-sync' (called "house-sync") device providing this signal
to the cameras and acquisiion hardware. I've never used a Peak system.

I imagine you might need to do some rudimentary signal processing to
the line-lock signal if the voltage level pulse from the genlock is
below TTL (??) or is not flat. Maybe a simple Schmidt trigger of some
such would suffice. I'm sure lots of people on this same news group
with an EE background could answer this in a nanosec. ;)

Then, route the pulse into your parallel port on your PC and write an
interrupt service routine that counts pulses (the line frequency for PAL
is 625/50 HZ = 15,625 HZ) and sets a flag to tell the data acquision
loop to buffer your other data accordingly.

HTH,
Ted

Ted Morris
tmorris@me.umn.edu 612-625-3520
Center For Advanced Manufacturing Design And Control 612-625-9881
Institute of Technology, U of Minnesota FAX: 612-625-8884
---------------------------------------------------------------------------
"McBride fell 12 stories, hitting the pavement like a Hefty Bag filled
with vegetable soup." (Paul Sabourin, Silver Spring)

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Dear Susan;

I am not sure, exactly, what you are doing; But, I may be able to
help. Our company designed and builds the cameras for Peak. I hope
that they are working well for you.

Could you please give me some more details on how you synchronize the
EMG and force plate with the 50Hz cameras? I think that Peak may
have already solved this, but if they haven't it may be possible for
us to make up some sort of interface box.

Best regards (from sunny California!)

Peter Chupity
JC Labs, Inc.
1059 Wright Ave.
Mountain View, CA 94043
Tel: +1 650 967 3431 Fax: +1 650 967 3439


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Dear Susan

I have received your request already through Kistler USA and have forwarded
it
to our rep in Australia "John Morris". We have a "Video Synchronizer" which
will
probably do the job but we have not tested it with 200Hz. Warren Brooks or
somebody else at John Morris is getting in contact with you soon.

Best Regards
Christian Calame
Product Manager Biomechanics
-----------------------------------------------------------
Christian Calame
Product Manager Biomechanics
Kistler Instrumente AG Winterthur, P.O.Box 304,
CH-8408 Winterthur, Switzerland
Tel: +41 52 224 11 11, Fax: +41 52 224 14 14
Telex 896 296 KAG CH,
E-Mail: cl@kistler.ch
-----------------------------------------------------------


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Susan:
we use the same 200Hz camera as you (actually made for Peak by JC Labs, I
believe).
if you use an LED (Light Emiting Diode) it can easily be detected in a
single video field .
An incadescent lamp (i.e. like Thomas Edison invented) takes a long time to
become bright. LED's are nearly instant on/off.


Rodger Kram
Assistant Professor


mail address:
Integrative Biology Dept.
3060 VLSB
University of California
Berkeley, CA 94720-3140

office: 5024 VLSB
phone (510) 643-9370
FAX (510) 643-6264
e-mail rkram@socrates.berkeley.edu
WWW http://socrates.berkeley.edu:80/~rkram/


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