Problem with 32 channel headbox / EKG

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kaplan21
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Joined: Thu Apr 05, 2018 9:37 pm

Problem with 32 channel headbox / EKG

Post by kaplan21 » Thu Apr 05, 2018 9:43 pm

I'm having a problem with some equipment. We use an ActiveTwo system, with a 32 channel passive headbox. We plug a 32 channel ribbon into the A1-32 port for EEG collection, and the headbox into the B1-32 port to collect EKG and startle data. On one of our units, ActiView is not picking up any data from the headbox. I know it's not a problem with the hardware on the headbox, because when it's plugged into the A1-32 port, the data shows up on ActiView. I'm not sure if this is an issue with software configuration that can be fixed, or if it's an issue with the hardware (possibly the ports). If anyone has an idea, let me know! (If you need more technical information or details about the equipment, let me know - I'm fairly new to using the equipment).

Thanks!

Coen
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Re: Problem with 32 channel headbox / EKG

Post by Coen » Fri Apr 06, 2018 2:06 pm

Check whether there are actually Amp/ADC modules installed on the B channels (inspect offsets with nothing connected to the AD-box).

Best regards, Coen

kaplan21
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Joined: Thu Apr 05, 2018 9:37 pm

Re: Problem with 32 channel headbox / EKG

Post by kaplan21 » Fri Apr 06, 2018 5:23 pm

I don't think there are Amp/ADC modules installed on the B channels. Is there a way to install them?

Coen
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Re: Problem with 32 channel headbox / EKG

Post by Coen » Fri Apr 06, 2018 9:11 pm

Run the system with no electrodes connected: channels with offset at minimum (-262 mV) are installed, channels with offset at zero are not installed.

Purchase 8-channel modules (EUR 1600) for the additional channels you want to use and install them in the proper slots in the motherboard.

Best regards, Coen (BioSemi)

Juliette
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Joined: Tue Sep 04, 2018 3:39 pm

Re: Problem with 32 channel headbox / EKG

Post by Juliette » Tue Feb 26, 2019 10:29 am

Hi,

I'll continue this topic as I have questions related to the same issue.

My current set-up consists in :
- 64 active-type electrodes for EEG (A1-32 and B1-32 ports of the A/D Box), with CMS/DRL plugged on the headcap
- 11 flat-type electrodes for ECG, EOG and EMG (EX1-8 channels and additionnal channels (Headbox on C1-32 port of the A/D Box))

Question 1 :
I think Amp / ADC modules are not installed on the C channels.
Could you please explain me how to do it (level : beginner) ?

Question 2 :
With the configuration described above, should I plug an additionnal CMS/DRL chord ? If yes, should it be on the A/D Box or on the Headbox ?
And which locations would you recommend on the subject's body ?


Thank you in advance for your help,
Best,

Juliette

Coen
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Re: Problem with 32 channel headbox / EKG

Post by Coen » Tue Feb 26, 2019 4:07 pm

>Question 1 :
>I think Amp / ADC modules are not installed on the C channels.
>Could you please explain me how to do it (level : beginner) ?

See my earlier post in this thread about hwo to check which channels are installed.

Contact BioSemi directly for purchase and installation of more channels.

>Question 2 :
>With the configuration described above, should I plug an additionnal CMS/DRL chord ?

Use either a CMS/DRL integrated with the A set, or a seperate CMS/DRL chord (if your A set has no CMS/DRL).

> If yes, should it be on the A/D Box or on the Headbox ?

To the A/D box when the Headbox is connected to B - H
Eitehr to Headbox or A/D-box when Headbox is connected to A.

And which locations would you recommend on the subject's body ?

CMS approx in the center of the other electrodes
DRL can be anywhere on the body

Best regards, Coen (BioSemi)

Robbie303
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Re: Problem with 32 channel headbox / EKG

Post by Robbie303 » Tue Feb 26, 2019 4:13 pm

Dear Juliette,

First you need to know how many channels are installed in SCSI connector C1-32.
You can find out how many hardware channels are installed inside your AD-box by running ActiView. Select the 'Offset' page in ActiView with no electrode sets inserted in the AD-box. When a channel is installed, then the offset will be maximum negative. When a channel is not installed, then the offset of that channel will be zero.

For the moment I will assume that currently your AD-box has the following channels installed:
A1-A32 SCSI connector: 32 channels installed (4 modules)
B1-B32 SCSI connector: 32 channels installed (4 modules)
C1-C32 SCSI connector: 8 channels installed (1 module)
EX1-EX2: 8 channels installed (1 module)

In this supposedly current configuration you can connect the following electrodes:
1 x P32 electrode set to SCSI connector A
1 x P32 electrode set to SCSI connector B
8 x TP electrodes to the TouchProof inputs EX1-EX8
8 x TP electrodes to the Headbox which is connected to SCSI connector C. (when the Headbox would be connected to SCSI connector B, than 32 inputs will be operational on the Headbox)

If you want to be able to connect more TP electrodes, than additional channels need to be installed in SCSI connector C.
With 3 extra modules (24 channels) there will be a total of 32 channels installed in SCSI connector C. Then you will have 32 operational inputs on the Headbox when connected to SCSI connector C.

Each 8 channel module costs 1600 Euro.
When you want extra modules to be installed inside your AD-box, than it is best to ship your AD-box to us, so we can install the modules and check everything.

There can only be 1 CMSDRL connected at the same time.
So, either you use a P32 set with integrated CMSDRL at SCSI connector A, or you use a separate CMSDRL cord at the CMSDRL input on the front of the AD-box, or you use a separate CMSDRL cord on the CMSDRL input on the Headbox.


In practise, the location of the CMS and DRL is not very critical.
When the CMSDRL are placed at a not ideal location, than the amount of common mode present in the signal will be a bit higher.
The Ideal location of the CMS electrode is in the middle of the measuring electrodes.
The ideal location of the DRL is away from the measuring electrodes.
This will result in the best CMRR, resulting in the least possible amount of 50 Hz noise.
During a bucket test, you can experiment with moving the CMS and DRL electrodes inside the bucket. When moving the CMS and DRL to various locations, you will see that this will have an effect on the common mode, 50 Hz.

So, for example when measuring ECG with 8 TP FLAT electrodes on the chest.
- place the CMS in the middle of the FLAT electrodes.
- place the DRL somewhere on an arm or a leg.

The location of the CMS and DRL does also not influence the amplitude of the measuring electrodes.
This is because after referencing, the CMS signal is subtracted again.
ActiView always saves the signals 'raw, in your analysis software you should always select a reference (1 of the measuring electrodes)
The referencing, you will give you 40 dB extra CMRR (Common mode rejection ratio)
https://www.biosemi.com/faq/cms&drl.htm

PS: always use Elefix with FLAT electrode. Signa gel is only suitable for use with PIN electrode on the head.

Best regards,
Robert Honsbeek

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