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