Did anybody use function generator to diagnose the system?

[Reinhard]

Hi, 

Since I didn't get the signal from my cultured MEA, I returned to check the system hardware. I tried to connect the pins of MCS preamplifier to the signal probe a function generator. But it has some problems. 

1. How could I tell the system is working well? 

No matter what kind of signals (shape, amplitude and frequency) I input, NR finally gave me a +/-10mV square signal. In this case, I didn't know why the GND channel have the same signal.

2. The minimum amplitude of my function generator is 10mVpp, so is there anyway I can do to input a smaller V? I tried to use some resistances, but the signal is overlapped by the noise. I can see the amplitude of the noise changed with the input amplitude, but I can't see the shape of the wave. 

3. Sometimes the noise will become larger, but it will return to smaller status if I restarted the power. They are all in the +/-39uV range. It is normal?

[Jon Newman]

1. The four channels in the corners are not connected to anything, at least on our rigs. What you are seeing is an amplifier with large gain and a disconnected input, which will bounce back and form between the power rails. This has nothing to do with the signal you are sending to the MEA.

By the way, how are you getting signals from the function generator into the MEA? Are you using the test MEA provided by MCS?

2. The test MEA from MCS has a ~1000:1 divider on it. We were going over it in this thread, which concluded with Jon E requesting a circuit diagram for your stimulation. Please respond to that post -- we cannot help otherwise.

https://groups.google.com/d/topic/neurorighter-users/n6bxfMeSJNg/discussion

3. I don't understand what you are asking. The RMS noise should be on the order of 8-10 uV. This means the peak to peak voltage noise, which you can better estimate just by looking at the waveforms, should be around 24-30 uV.

--
You received this message because you are subscribed to the Google Groups "NeuroRighter Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to neurorighter-us...@googlegroups.com.
To post to this group, send email to neurorigh...@googlegroups.com.
Visit this group at http://groups.google.com/group/neurorighter-users.
For more options, visit https://groups.google.com/d/optout.

--

Jonathan Newman

Postdoctoral Fellow, MIT

http://www.mit.edu/~jpnewman/

[Reinhard]

Hi, Jon,

1. I input the signal into preamplifier directly. As shown in the below, I connect the probe of function generator to the pins and GND of the preamplifier directly. Of course, the pins didn't contact to the bottom stage of the preamplifier to avoid the grounding.

2. According to my experience, when I input a signal into the test MEA from MCS, the amplitude shown in the NR is reduced about 120-130 times against the function generator output. For example, when a sine voltage of 200mVpp and 20HZ was input into the testchip, the NR gave a signal of 1600uVpp. 

However, the previous test of the 1000:1 divider was done on the test chip alone. 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.  I have responded in the previous post.

3. Sorry for my poor explanation. The noise in the left of that picture is apparently larger than the right part. The only difference is that I restarted the power, and the noise reduced to the status in the right picture. However, after a while, the noise would return to the status in the left part. Is this normal? If not, which noise is more close to your setup? The power we used is a DC power (GPS-4303) from GWInstek instead of a battery.

On Sunday, April 19, 2015 at 10:26:10 PM UTC+8, Jon Newman wrote:

1. The four channels in the corners are not connected to anything, at least on our rigs. What you are seeing is an amplifier with large gain and a disconnected input, which will bounce back and form between the power rails. This has nothing to do with the signal you are sending to the MEA.

By the way, how are you getting signals from the function generator into the MEA? Are you using the test MEA provided by MCS?

2. The test MEA from MCS has a ~1000:1 divider on it. We were going over it in this thread, which concluded with Jon E requesting a circuit diagram for your stimulation. Please respond to that post -- we cannot help otherwise.

https://groups.google.com/d/topic/neurorighter-users/n6bxfMeSJNg/discussion

3. I don't understand what you are asking. The RMS noise should be on the order of 8-10 uV. This means the peak to peak voltage noise, which you can better estimate just by looking at the waveforms, should be around 24-30 uV.

On Sat, Apr 18, 2015 at 3:45 AM, Reinhard <laos...@gmail.com> wrote:

Hi, 

Since I didn't get the signal from my cultured MEA, I returned to check the system hardware. I tried to connect the pins of MCS preamplifier to the signal probe a function generator. But it has some problems. 

1. How could I tell the system is working well? 

No matter what kind of signals (shape, amplitude and frequency) I input, NR finally gave me a +/-10mV square signal. In this case, I didn't know why the GND channel have the same signal.

2. The minimum amplitude of my function generator is 10mVpp, so is there anyway I can do to input a smaller V? I tried to use some resistances, but the signal is overlapped by the noise. I can see the amplitude of the noise changed with the input amplitude, but I can't see the shape of the wave. 

3. Sometimes the noise will become larger, but it will return to smaller status if I restarted the power. They are all in the +/-39uV range. It is normal?

--
You received this message because you are subscribed to the Google Groups "NeuroRighter Users" group.

To unsubscribe from this group and stop receiving emails from it, send an email to neurorighter-users+unsub...@googlegroups.com.

To post to this group, send email to neurorigh...@googlegroups.com.
Visit this group at http://groups.google.com/group/neurorighter-users.
For more options, visit https://groups.google.com/d/optout.

[Jon Newman]

OK, I see that on this thread that you are using the amplifier. I will have a closer look at this shortly.

To unsubscribe from this group and stop receiving emails from it, send an email to neurorighter-us...@googlegroups.com.

To post to this group, send email to neurorigh...@googlegroups.com.
Visit this group at http://groups.google.com/group/neurorighter-users.
For more options, visit https://groups.google.com/d/optout.

--

Jonathan Newman

Postdoctoral Fellow, MIT

http://www.mit.edu/~jpnewman/

--

You received this message because you are subscribed to the Google Groups "NeuroRighter Users" group.

To unsubscribe from this group and stop receiving emails from it, send an email to neurorighter-us...@googlegroups.com.

To post to this group, send email to neurorigh...@googlegroups.com.
Visit this group at http://groups.google.com/group/neurorighter-users.
For more options, visit https://groups.google.com/d/optout.