about USB-ME64

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about USB-ME64

Post  holly87 on Sun Apr 01, 2012 1:56 am

Hi,
I am using a USB-ME64 system, composed of a MEA1060 pre-amplifiers, a FA64 filter amplifier and the USB data acquisition card.

I read that in the 68-pin MCS cable connecting all the abovementioned devices there is a pin (pin number 2) that carries the "signal ground".
I would be very grateful if you could clarify me some concepts.

1) The A/D card takes measurements in reference to this signal?
2) This "signal ground" is the signal taken by the reference electrode of the MEA chip? If so, the reference electrode is linked to pin 2 of the MCS cable contacting the MEA1060 amplifier, is that correct?


Thank you

best regards

Giulia Smile




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Re: about USB-ME64

Post  Frank MCS on Sun Apr 01, 2012 8:58 pm

Hi Giulia,
you are right, pin 2 of the cable is what the internal ref and everything pluged in the ground connectors at the amplifier is connected to, and this serves as reference for the A/D.

Best regards Frank
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Re: about USB-ME64

Post  holly87 on Sun Apr 01, 2012 9:25 pm

Ok, thank you!

If I correctly understand, the 7 "GND" contacts of the amplifier (page 27 of the manual http://www.multichannelsystems.com/sites/multichannelsystems.com/files/documents/manuals/MEA1060-Inv-BC_Manual.pdf) are connected to pin 2. And also electrode 15, since I have to physically connect it to one of these contacts. I thought that they were connected to pin 1, i.e to the Power ground!

So, in my setup a differential measurement is performed only at the level of A/D card...With differetianl measurement I mean a differential amplification between the band-passed version of each channel and of el 15, which is necessary before digital conversion to match the ADCs range..is that right?

If I want a differential measurement to be performed before in the signal chain (i.e. at the level of the filter amplifier), should I buy a FA64 with differential channels or the PGA device, right?

Thank you very very much Very Happy

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Re: about USB-ME64

Post  Frank MCS on Sun Apr 01, 2012 11:04 pm

Hi Giulia,
sorry, I misunderstood your question. Indeed the differencial signal between signal electrode and ground electrode is amplified, while the ground electrode is connected to the system ground. The A/D only digitizes this signal.

I hope this is what you need Frank
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Re: about USB-ME64

Post  holly87 on Mon Apr 02, 2012 12:40 am

Ok
I did not know that MEA1060 is a differential pre-amplifier! Since my FA64S is not differential (as written in MCS web site), I wrongly thought that inside the A/D cards there is a differential amplifier before the analog to digital converters! Embarassed

So, the MEA1060 amplifies the difference between each electrode and electrode 15. Then, each amplified signal goes to its corresponding pin of the MCS cable that connects the pre-amp to the FA64S, while electrode 15 is connected to the power ground (which comes from pin 1) and goes to pin 2..

I hope I really understood how it works...>)

thank you!!!

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