Headbox ACT32 problem if more than 8 channels measured

[lexvanrooij]

We have a Headbox ACT32 connected to an AD-box at channels B1-B32. When we connect more than 8 electrodes (i.e. C9 and up) the electrode offset of ALL electrodes goes to its maximum value. We are taking care of good connections for all electrodes. Furthermore, we have CMS/DRL connected to the AD-box on A1-A32.

What could be our problem? Bad or damaged electrodes or should we connect differently?

Thanks,
Lex

[Coen]

Do you have modules installed in your AD-box for channels B9 and up ? Connecting an active electrodes to an AD-box channel without an amplifier/converter modules installed for that channel, will make the blue light flash (and power shut down for all active electrodes).

Check as follows for which channels modules are installed in the AD-box. Run the AD-box without any electrodes connected to it. Check the offsets. Empty channels show an offset of zero, whereas installed channels show a maximally negative offset.

Best regards, Coen

[lexvanrooij]

Coen,

When connected as above, only B1-B8 show large negative electrode offset. This probably means we need to install amplifier/converter modules. How do we do this?

Regards,
Lex

[Coen]

Purchase extra amplifier/converter modules from BioSemi.

Best regards, Coen (BioSemi)

[Ignacio]

Hi Coen,

I got an old MK1 (ADC11). So, as you indicated here, in order to check which amplifier modules are installed in the AD-box I run the AD-box without any electrodes connected to it (using the setting/wiring of a MK2).

Results:
A1 to A14 show a maximally negative offset.
A15 to B19 show an alternating offset (going crazily up and down in a fast way, like ~3hz)
Above B20 offset is zero.

Checking the mono polar display, A1 to A13 seem pretty stable, but from A14 (despite A14 has a stable offset) to B19 look like a square wave oscillator.

Therefore, I would greatly appreciate your help for diagnosing this AD-box.
Best Regards,
Ignacio

[Coen]

What is the serial number ?

[Ignacio]

Serial No: ADC9-04-147
(Model says : ActiveTwo AD-box ADC-11)

[Coen]

That should be a 32+8 channel system with 4 active BSPM electrode strips, special low gain version (LSB = 125 nV).

Without electrode sets connected to the AD-box, A1-A32 and EX1-EX8 should be maximally negative, rest is zero.

If not, please contact your local BioSemi representative for further support.

Best regards, Coen (BioSemi)

[Ignacio]

That helps! Thank you Coen.