The same signal is observed in multiple channels.

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Reinhard

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Dec 2, 2014, 1:22:15 AM12/2/14
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Hi, Everyone,

When I was diagnosing the system, I found a strange phenomenon. I used a functional generator to generate a sine signal, and input it via the either SCB68A box (we connect the output of functional generator to the socket in the box ) or PCB board. A sine signal appears in the NR. Strangely, some other channels showed the same signal while we are pretty sure only one channel is connected to the functional generator. How could it happened?

Furthermore, we tried to connect the output of functional generator to the pins of preamp, but no signals can be seen in the NR. Does it indicate a problem in preamp, or our diagnosis method is wrong?

The last thing is that we can not see the input sine signal in the NI MAX software while we can saw more than one sine signals in NR. Could you guys give us some suggestions?

Jon Newman

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Dec 7, 2014, 10:26:17 PM12/7/14
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On Tue, Dec 2, 2014 at 1:22 AM, Reinhard <laos...@gmail.com> wrote:
Hi, Everyone,

When I was diagnosing the system, I found a strange phenomenon. I used a functional generator to generate a sine signal, and input it via the either SCB68A box (we connect the output of functional generator to the socket in the box ) or PCB board. A sine signal appears in the NR. Strangely, some other channels showed the same signal while we are pretty sure only one channel is connected to the functional generator. How could it happened?

It could happen a bunch of different ways

The other channels are not connected. This means they are just wires tied to the input of differential amplifier (extremely high input impedance) therefore they act as antennas and pick up the sine wave on the active channel. Try grounding the unsued channels, or better yet, use a test mea.
 

Furthermore, we tried to connect the output of functional generator to the pins of preamp, but no signals can be seen in the NR. Does it indicate a problem in preamp, or our diagnosis method is wrong?

It sounds like your amp is not powered.
 

The last thing is that we can not see the input sine signal in the NI MAX software while we can saw more than one sine signals in NR. Could you guys give us some suggestions?

NR's recording hardware does two things

1. It maps the MCS amplifier channels to the NI cards. This is totally passive (just wiring connections)
2. It provides regulated power to the amplifier. I have a feeling this is not working for you. have you measured the voltage rails produced by the NeuroRighter PCB??

NI MAX and NR use the same drivers to capture data, so really they are quite similar at the base. I don't know what's up with MAX. 

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Reinhard

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Dec 8, 2014, 4:56:56 AM12/8/14
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Hi, Jon,

Thank you so much! We don't know why and did nothing, but now, when we input the signal from SCB box, we only observed the sine signal in one channel. 

For the power supply of the preamp, we check the voltage from the MCS cable, it is +/- 6V.

Now, the problem to us is how to make sure the preamp is good or not. We tried to input the signal from the test MEA (signal of function generator connected to signal socket, signal ground of function generator connected to one of the GND socket and the left GND connected to preamp ground). In this case, no signal is shown in NR. Then we tried to connect the pin of preamp to signal of function generator and connect the signal GND to preamp GND, nothing happened. Could you give us some suggestions on how to use the test MEA and preamp?

Furthermore, you mentioned many times about the ground of wires in the SCB68A. We just connect 17 wires to the AI channels and AI SENSE, and left other 17 wires are just left and unconnected in the box like in the attached picture. Because I think they have already grounded in the MCS covertor PCB, right? If we need to connect the 17 wires to AI GND, there are only 8 AI GND, how could we connect them all?


On Monday, December 8, 2014 11:26:17 AM UTC+8, Jon Newman wrote:
On Tue, Dec 2, 2014 at 1:22 AM, Reinhard <laos...@gmail.com> wrote:
Hi, Everyone,

When I was diagnosing the system, I found a strange phenomenon. I used a functional generator to generate a sine signal, and input it via the either SCB68A box (we connect the output of functional generator to the socket in the box ) or PCB board. A sine signal appears in the NR. Strangely, some other channels showed the same signal while we are pretty sure only one channel is connected to the functional generator. How could it happened?

It could happen a bunch of different ways

The other channels are not connected. This means they are just wires tied to the input of differential amplifier (extremely high input impedance) therefore they act as antennas and pick up the sine wave on the active channel. Try grounding the unsued channels, or better yet, use a test mea.
 

Furthermore, we tried to connect the output of functional generator to the pins of preamp, but no signals can be seen in the NR. Does it indicate a problem in preamp, or our diagnosis method is wrong?

It sounds like your amp is not powered.
 

The last thing is that we can not see the input sine signal in the NI MAX software while we can saw more than one sine signals in NR. Could you guys give us some suggestions?

NR's recording hardware does two things

1. It maps the MCS amplifier channels to the NI cards. This is totally passive (just wiring connections)
2. It provides regulated power to the amplifier. I have a feeling this is not working for you. have you measured the voltage rails produced by the NeuroRighter PCB??

NI MAX and NR use the same drivers to capture data, so really they are quite similar at the base. I don't know what's up with MAX. 

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Jon Newman

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Dec 8, 2014, 9:41:11 AM12/8/14
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On Mon, Dec 8, 2014 at 4:56 AM, Reinhard <laos...@gmail.com> wrote:
Hi, Jon,

Thank you so much! We don't know why and did nothing, but now, when we input the signal from SCB box, we only observed the sine signal in one channel. 

For the power supply of the preamp, we check the voltage from the MCS cable, it is +/- 6V.

Now, the problem to us is how to make sure the preamp is good or not. We tried to input the signal from the test MEA (signal of function generator connected to signal socket, signal ground of function generator connected to one of the GND socket and the left GND connected to preamp ground). In this case, no signal is shown in NR. Then we tried to connect the pin of preamp to signal of function generator and connect the signal GND to preamp GND, nothing happened. Could you give us some suggestions on how to use the test MEA and preamp?

The test MEA is a 1000:1 voltage divider so that a 1 volt input signal will appear as 1 mV on the scope screen. Are you zooming the the display in to see the smaller signal?

Furthermore, you mentioned many times about the ground of wires in the SCB68A. We just connect 17 wires to the AI channels and AI SENSE, and left other 17 wires are just left and unconnected in the box like in the attached picture. Because I think they have already grounded in the MCS convertor PCB, right? If we need to connect the 17 wires to AI GND, there are only 8 AI GND, how could we connect them all?

They can be left unattached because they are attached to ground on the amplifier side and therefore should be acting as a small amount of shielding in their current state.

 
On Monday, December 8, 2014 11:26:17 AM UTC+8, Jon Newman wrote:


On Tue, Dec 2, 2014 at 1:22 AM, Reinhard <laos...@gmail.com> wrote:
Hi, Everyone,

When I was diagnosing the system, I found a strange phenomenon. I used a functional generator to generate a sine signal, and input it via the either SCB68A box (we connect the output of functional generator to the socket in the box ) or PCB board. A sine signal appears in the NR. Strangely, some other channels showed the same signal while we are pretty sure only one channel is connected to the functional generator. How could it happened?

It could happen a bunch of different ways

The other channels are not connected. This means they are just wires tied to the input of differential amplifier (extremely high input impedance) therefore they act as antennas and pick up the sine wave on the active channel. Try grounding the unsued channels, or better yet, use a test mea.
 

Furthermore, we tried to connect the output of functional generator to the pins of preamp, but no signals can be seen in the NR. Does it indicate a problem in preamp, or our diagnosis method is wrong?

It sounds like your amp is not powered.
 

The last thing is that we can not see the input sine signal in the NI MAX software while we can saw more than one sine signals in NR. Could you guys give us some suggestions?

NR's recording hardware does two things

1. It maps the MCS amplifier channels to the NI cards. This is totally passive (just wiring connections)
2. It provides regulated power to the amplifier. I have a feeling this is not working for you. have you measured the voltage rails produced by the NeuroRighter PCB??

NI MAX and NR use the same drivers to capture data, so really they are quite similar at the base. I don't know what's up with MAX. 

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Reinhard

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Dec 9, 2014, 9:21:51 PM12/9/14
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Hi, Jon,

Could we input a 1 volt signal into test MEA with damage on the preamp? Because we didn't know the test MEA is a 1000:1 voltage divider, so we just input a 10 mV signal, that's maybe the reason we can't see anything in the NR. If we correctly input a signal from test MEA and which channel will is occurs?  One more thing, however, we tried to input 10 mV signal from the pins of preamp directly without test MEA, still no signals.

Thank you so much!


On Monday, December 8, 2014 10:41:11 PM UTC+8, Jon Newman wrote:
On Mon, Dec 8, 2014 at 4:56 AM, Reinhard <laos...@gmail.com> wrote:
Hi, Jon,

Thank you so much! We don't know why and did nothing, but now, when we input the signal from SCB box, we only observed the sine signal in one channel. 

For the power supply of the preamp, we check the voltage from the MCS cable, it is +/- 6V.

Now, the problem to us is how to make sure the preamp is good or not. We tried to input the signal from the test MEA (signal of function generator connected to signal socket, signal ground of function generator connected to one of the GND socket and the left GND connected to preamp ground). In this case, no signal is shown in NR. Then we tried to connect the pin of preamp to signal of function generator and connect the signal GND to preamp GND, nothing happened. Could you give us some suggestions on how to use the test MEA and preamp?

The test MEA is a 1000:1 voltage divider so that a 1 volt input signal will appear as 1 mV on the scope screen. Are you zooming the the display in to see the smaller signal?

Furthermore, you mentioned many times about the ground of wires in the SCB68A. We just connect 17 wires to the AI channels and AI SENSE, and left other 17 wires are just left and unconnected in the box like in the attached picture. Because I think they have already grounded in the MCS convertor PCB, right? If we need to connect the 17 wires to AI GND, there are only 8 AI GND, how could we connect them all?

They can be left unattached because they are attached to ground on the amplifier side and therefore should be acting as a small amount of shielding in their current state.

 
On Monday, December 8, 2014 11:26:17 AM UTC+8, Jon Newman wrote:
On Tue, Dec 2, 2014 at 1:22 AM, Reinhard <laos...@gmail.com> wrote:
Hi, Everyone,

When I was diagnosing the system, I found a strange phenomenon. I used a functional generator to generate a sine signal, and input it via the either SCB68A box (we connect the output of functional generator to the socket in the box ) or PCB board. A sine signal appears in the NR. Strangely, some other channels showed the same signal while we are pretty sure only one channel is connected to the functional generator. How could it happened?

It could happen a bunch of different ways

The other channels are not connected. This means they are just wires tied to the input of differential amplifier (extremely high input impedance) therefore they act as antennas and pick up the sine wave on the active channel. Try grounding the unsued channels, or better yet, use a test mea.
 

Furthermore, we tried to connect the output of functional generator to the pins of preamp, but no signals can be seen in the NR. Does it indicate a problem in preamp, or our diagnosis method is wrong?

It sounds like your amp is not powered.
 

The last thing is that we can not see the input sine signal in the NI MAX software while we can saw more than one sine signals in NR. Could you guys give us some suggestions?

NR's recording hardware does two things

1. It maps the MCS amplifier channels to the NI cards. This is totally passive (just wiring connections)
2. It provides regulated power to the amplifier. I have a feeling this is not working for you. have you measured the voltage rails produced by the NeuroRighter PCB??

NI MAX and NR use the same drivers to capture data, so really they are quite similar at the base. I don't know what's up with MAX. 

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Jon Newman

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Dec 9, 2014, 9:28:54 PM12/9/14
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On Tue, Dec 9, 2014 at 9:21 PM, Reinhard <laos...@gmail.com> wrote:
Hi, Jon,

Could we input a 1 volt signal into test MEA with damage on the preamp?
Its operating on +/- 6 V rails so no. The NI DAQ operates on +/- 10 Volt rails so the output of the amp is just swinging back and forth between +/- 6 volts and thats still within the acceptable input range of the NI DAQ.

 
Because we didn't know the test MEA is a 1000:1 voltage divider, so we just input a 10 mV signal, that's maybe the reason we can't see anything in the NR.

Yes, that would result in

10 mV/1000 = 10 uV, which is right down near the noice floor of the recording.
 
If we correctly input a signal from test MEA and which channel will is occurs?

I hope if you put in a volt you can see it. 
 One more thing, however, we tried to input 10 mV signal from the pins of preamp directly without test MEA, still no signals.

Thats a problem, you should certainly be able to see that on the NR screen. Go to take an oscope or multimeter to the corresponding pin on the breakout box after amplification and make sure the signal is reaching the the NI DAQ through the amplifier. You should see

10 mV * 1200 =  12V which is beyond the +/-6V rails, so you should see a chopped sine wave at +/-6 volts.

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Reinhard

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Dec 9, 2014, 10:54:02 PM12/9/14
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Hi, Jon, 

I'm still a little confusing about the test MEA. I asked whether I can try to input a 1 volt signal, you said "Its operating on +/- 6 V rails so no." I'm not sure why the answer is "no". With my understanding, if I input 1 volt, it will be divided by test MEA, so the preamp will detect a signal of 1V/1000=1mV, and after our amps, the signal will be 1mV*1100=1.1V. It's still in the range of =/-6V, right? It couldn't damage the system, and we should see a 1.1V signal in the NR. Correct?

Jon Newman

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Dec 10, 2014, 12:10:22 AM12/10/14
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On Dec 9, 2014 10:54 PM, "Reinhard" <laos...@gmail.com> wrote:
>
> Hi, Jon, 
>

> I'm still a little confusing about the test MEA. I asked whether I can try to input a 1 volt signal, you said "Its operating on +/- 6 V rails so no." I'm not sure why the answer is "no". With my understanding, if I input 1 volt, it will be divided by test MEA, so the preamp will detect a signal of 1V/1000=1mV, and after our amps, the signal will be 1mV*1100=1.1V. It's still in the range of =/-6V, right? It couldn't damage the system, and we should see a 1.1V signal in the NR. Correct?

That is correct. I misunderstood your wording.

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Reinhard

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Dec 10, 2014, 12:21:54 AM12/10/14
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Thank you for your patience and great help!

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Reinhard

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Jan 6, 2015, 2:48:13 AM1/6/15
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Dear Jon,

I hope you had a nice holiday! I still can't see anything and the guy from MCS company said the test60 MEA is not a voltage divider. Did you use the same test MEA? And one more thing, if the signal can be fed in from the test MEA, in which channel I can see it?

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Jon Newman

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Jan 7, 2015, 8:29:59 AM1/7/15
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On Tue, Jan 6, 2015 at 2:48 AM, Reinhard <laos...@gmail.com> wrote:
Dear Jon,

I hope you had a nice holiday! I still can't see anything and the guy from MCS company said the test60 MEA is not a voltage divider. Did you use the same test MEA?

What is it then? I can literally see the divider on a picture of the circuit provided on its data sheet. 


it is between the test signal and one of the ground pins. This signal is then passed to a parallel RC combination meant to model a typical electrodes frequency response.
 
And one more thing, if the signal can be fed in from the test MEA, in which channel I can see it?


The test signal is sent to all channels.
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Jon Erickson

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Jan 7, 2015, 1:17:52 PM1/7/15
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Strictly speaking, this is a RC current divider, assuming that the
"GND" and "pad" connections have negligible resistance.

Anyway, for your test signals, are you sure you have the signal source
shorted to the amplifier ground, which is also shorted to the signal
ground?

Reinhard

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Jan 14, 2015, 3:50:06 AM1/14/15
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Hi, Jon,

The connection of function generator and test MEA should be right. And thank you for the information of test MEA, we tried to input a 3V DC voltage and detect a 3mV from the electrical pad. But a AC signal into the test MEA can not be detected . Is there any way to know whether the test MEA is working or not?
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Jon Erickson

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Jan 14, 2015, 3:59:21 PM1/14/15
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 we tried to input a 3V DC voltage and detect a 3mV from the electrical pad.

​Can you draw a diagram of your test circuit?  I am not quite sure how you measured Vout/Vin = 1/1000 in this case.​

 
But a AC signal into the test MEA can not be detected . Is there any way to know whether the test MEA is working or not?

If you can please share a diagram of your test circuit​ that might help understand what you are seeing and why.  In general, the pads are large enough that you could just use ohm-meter to check for the 220 k resistor.  You could set up a voltage divider and vary frequency to see the effect of the capacitor acting as short at very high frequencies and open at low ones.  
 
I guess it is possible, but unlikely, that MCS made a defective test MEA...


 
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Reinhard

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Apr 24, 2015, 5:14:18 AM4/24/15
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Hi, Jon,

The test circuit is drawn in the below. The +/- probe of the power are connect to the Signal and GND socket of test chip. A multimeter is used to measure the voltage from another GND socket and the outer electrical pad. 

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Jon Newman

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Apr 24, 2015, 11:13:03 AM4/24/15
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OK,

Is this literally the circuit you are using, or are you just showing all these leads for demonstration purposes?

e.g. where is the amplifier?

Jon

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Reinhard

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Apr 25, 2015, 10:17:30 PM4/25/15
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This circuit is the one used to demonstrate whether the test chip is a 1000:1 divider. We didn't use the amplifier for this purpose. Of course, we installed the test chip into amplifier and see the signal from NR if we tried to input some sine signal.
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Nealen Laxpati

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Apr 25, 2015, 10:19:13 PM4/25/15
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Haha
Neal
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