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mprado68
03-19-2009, 12:31 AM
Dear all,



Here is the summary of responses to my question about "connecting Kistler force platforms to Vicon". I want to specially thank Gordon Robertson and Liz Nottingham (Vicon Support) for their help.



And I also want to summarize my conclusions:



Kistler platforms can be connected to Giganet of Vicon in two ways:



1] Using one PC with Vicon software (Nexus or Workstation) to record data and control cameras and another PC with Bioware software to supply power and control the force platforms. It is the following configuration:



Kistler force platforms with built-in amplifier -> Kistler 5606 connection box ->

from 5606 2 A/D board -> Bioware PC

from 5606 16 bnc connectors-> Vicon MX Giganet -> Nexus PC



2] Only one PC with Vicon software (Nexus or Workstation) to record data and control cameras and Kistler 5322A2 control unit to supply power to the force platforms and manually control them. It is the following configuration (that I did´t check):



Kistler force platforms with built-in amplifier -> Kistler 5322A2 control unit -> Vicon MX Giganet -> Nexus PC







* Gordon Robertson for University of Ottawa shared his experience using both systems:



We have done this successfully but we don't use Bioware to process the data and control the force plate. Instead the cabling goes directly into the analogue system of Vicon. Vicon needs to be setup to read the analogue data but the processing is done afterwards by Polygon or in our case we prefer Visual3D. You need to configure the Vicon Workstation so that that are correctly convert from voltages into newtons of force. You also need to exactly define the location of the force platform. This is all done within Workstation (or Nexus). There is s special Excel file that you can use to determine the coefficients necessary for the conversion. You also will need the scaling factors that Kistler provided with your force platform. Resetting of the force platforms will have to be done manually. There is no way )at least on our system) for the Vicon to send signals to the plate electronics.

If you need some help with the coefficients, I can send you a file or you could send me the factors from the Kistler force platform and I will compute them for you.

There is a box that comes with our Kistler 9286AA that supplies power to the amps and permits push-button control for gain and reset.

It’s model number is, 5322A2.

Have a look at this document: http://www.health.uottawa.ca/biomech/lab/docs/9286a.pdf



* Liz Nottingham (Vicon Support) also was a big help:



Dear Maria,

We saw your posting on BioMCH-L and thought I could help you out,

Sounds like your set up is correct, the 8 channels of your FP should be connected to your ADC box, then the 100 way connection cable should be attached to the giganets ADC card.

To connect kistler forceplates to Vicon, you must set up a few things in Vicon Nexus.

1. First set up a node for the force plate in the systems pane of Nexus. This can be done by right clicking on the "Force Plates" title in the pane. (see picture "AddFP")

2. Highlight this new FP in the resources list. Its properties will show up in the window below. Choose "show advanced" (blue) in the top of this window.

3. The first property to add in is the sensitivities. This can be found in your manual of your FP. It is specific to each individual FP's calibration. It also depends on the setting of the internal amplifier.

4. Now choose the ADC channels where each wire from the FP is connected to.

5. I suggest setting the "gain" to 10V, this is the limit of Voltage that Nexus will read in.

6. Now set the dimensions (found in manual), position, and orientation. Remember that the origin is based off of your "Set volume origin" calibration, and is defined as the middle marker in the 5 marker wand. The axes of your FP can be found in its manual. rotate it about the z axes until it lines up with the nexus global origin. (sometimes a guess and check method is best, stepping on the corners and checking the force vector displayed in the 3d perspective view)

7. The origin measurements need to be added in from the manual.

That should be it. Your FP will now be a green icon in the resources pane.

Save your system configuration so that you can access your defined force plate later on.

Best,

Liz Nottingham

Vicon Support.



Hi Maria,

For both internal and external amplified kistler forceplates we require a "control box" from the kistler FP to the ADC box. (breaks the signal out in analog through bnc cables). You will have to talk to kistler to get one of these.

Best,

Liz Nottingham

Vicon Support





Hi Maria,

We have an internal amplifier 9287BA, with control unit 5233A. So I would say that your probably on track, but I really have no kistler compatibility information here. I'll contact kistler and see what they tell me.

Best,

Liz Nottingham

Vicon Support



Hi Maria - see forwarded e-mail.

Yes, the 5233A2 with work with the 9286AA. Please contact me if I can be of any assistance to you on this.

Best regards,

Paul Bussman





* Florian Ullrich from Kistler, told me that the configuration I was using was ok, so I re-check everything until it works, so thank you so much



Dear Maria,
I don't know the MX Giganet from Vicon, but the configuration that you are describing is OK in general and should work as you expected!
The Kistler force platform should provide the signal for both data acquisition system connected via the distribution box 5606A (with the 16 BNC connectors on top).
If it works fine wit only BioWare atached it looks like connecting the Giganet is somehow pulling down the signal. This could be due to a to low resistance in the signal input. To measure voltage this input should have at least 100 kΩ resistence.
I suggest that you contact your Vicon dealer to verify that the analog BNC signals are connected correctly to the Giganet.
Best regards,
Florian Ullrich
Product Manager Biomechanics



*And other useful replies:





Hi Maria,
Firstly, we don't actually have a Vicon system as we use CODAmotion by Charnwood Dynamics. We do however have Bioware and two Kistler plates, so I will make some further assumptions for your system; if you are using the Kistler system with the 5606 connection box which supplies the force plates with power and basically re-routes the various signals and the Vicon MX Giganet with 64ch analog card.
The force plates have an integrated amplifier so their gain and control is controlled via the Digital controller card in the Bioware PC. The force data and any additional signals (eg via the 16 x BNC connectors on the top of the 5606) all pass along similar pins to the A/D analog card in the Bioware PC in the same way. If you wish to collect the force plate data with the Vicon system and control the plates with Bioware then you may want to consider disconnecting the A/D Board Analog 37-way D-connector on the 5606 box as it could be loading your system.
Let me know how you get on.
Kind regards,
Andreas Wallbaum
Senior Technician
Applied Biomechanics
School for Health
University of Bath, BA2 7AY





Have you checked whether the range settings on your amplifier match the range settings for the force plates in Vicon?

There will be a slight amount of drift that cannot be avoided, however if this is excessive (i.e. > 0.3pC/s) you may need to assess factors within the amplifer that may be causing the drift (e.g. insulation problems, defective MOSFET).

Hope this helps, Cheers,

Chris



Dear Maria,

The Vicon people will connect the Kistlers for you to their system allright. Otherwise you can search the Nexus hardware manual, but that is quite a job. In principle it comes to connecting the forceplate outputs directly to channels 1-12 of the Vicon A/D card ( do not use the Kistler A/D card) and setting some internal calibration file.

Yours,

At Hof

Center for Human Movement Sciences

University of Groningen

PO Box 196

9700 AD Groningen

The Netherlands





Hi there,

the sensitivities of your force platform must be converted by a certain

factor before you can type the matrix into your vicon software.

Therefore you need to contact your Vicon support. You will get an excel

sheet were you type in the calibration measurements of your calibration

certificate from Kistler (that was the way I did it here in munich).

I hope I will work...

Greets,

Michael Veith

Fachgebiet Biomechanik im Sport

Technische Universität München

Fakultät für Sportwissenschaft



Mar*a Prado, PhD

Dpt. Mechanical Engineering

University of Málaga

Campus El Ejido

29013 Málaga

Spain

Tel: +34 52 131314

Fax: +34 52 132691

Email: maria.prado@uma.es