I have a custom made breakout box which accepts 64 BNC channels and are sent to an AMUX-64t multiplexer. The issue I'm running into is with the DAQ we have in place. A third party board has about ± 0.1 V resolution when the data is run through it. The voltage from the BNC channels is stable to 0.0001 V, which is as low as I can measure, it may be more stable than this. Since there seems to be a major amount of noise in the signal, I'm looking for other options. We have an older model BNC-2090 that I ran the BNC outs straight into to see how the data looked without the intervening box and it's even worse. The noise puts the signal at ± 0.5 V noise. I'm looking into how to wire a butterworth filter into my software, but would be curious to hear about my hardware options. Since the multiplexer scans 16 channels at a time, can a high res 18-bit 16 channel board like the PCI-6280 be used to input/record the data? Are there others that would work? The cables would match (68 to 68 scsi), and if they are compatible I'd just have to figure out how to make a vi to view and record all 64 channels.
What kind of signals are you measuring? The PCI-6280 is compatible with the BNC-2090, you would have no problem using them together. Take into consideration that the PCI-6280 has 16 input channels when configured as RSE. I could recommend another PCI card with more information on what is it that you are trying to measure.
I hope this information was helpful.
They are ±10 V analog voltage signals (from an MTS flextest GT system). (BNC, AMUX-64t, DAQ card) We wouldn't use the bnc-2090 for collection. What we'd like ideally to use is the AMUX-64t to input the voltages from the multiplexer straight into a card like the 6280. Or any other compatible card. My assumption was that a 16 channel card might work if you could assign and create 64 virtual channels and have the data parsed out by labview.
I was checking out the AMUX-64t in depth and this is compatible with very old cards, this is very old. you would need a 32 AI card E Series. If you want to "multiplex" via software the channels you are going to have to stop and start tasks on your code all the time, and that will cost you resources and speed.
If you are planning to invest on a card I would suggest you getting the PCI-6225 which has 80 AI, 2 AO, 24 DIO and 2 Counters. This way you don't have to be worrying about multiplexing your channels.
Would using the PCI-6225 allow me to run the BNC cables into a connector block and then to the card instead of using the multiplexer? (BNC, connector block, PCI-6225) Also, what level of resolution would this give me in terms of decimal voltage? We would need a clean signal to ± 0.001 V, but would prefer ± 0.0001 V. Can this card provide that level of resolution that the pci-6289, 18-bit (or like card) delivers? those list 5.5 decimal precision. Nothing is listed on the 6225 page. How clean does the signal come through on a 16-bit card?
In order to give you the best advice, I'll need some more information about your system.
All 64 signals are in the range of +/- 10V? What kind of sensors are your reading from, can you attached the datasheet?
Yes, all signals are or will be ± 10 V. The MTS system has a gain value that would allow us to adjust any signal to output to 10 V if it wasn't.
MTS keeps a lot of their info proprietary, so it's hard to pin down exact specs. I've included the pdf for the product line with general specs. The channels read are from load and torque cells, a 6DOF cell, an lvdt, and a rotational encoder (I think that's what MTS is calling it, uses capacitance as feedback). The data is output through a "494.76 output BNC board" (p. 16) and at the bottom of (p. 19) it lists that it is 16-bit analog output resolution.
When I look at the data output from the MTS, I can reliably get 3 to 4 decimal resolution, depending on the channel. Force channels float more, but aren't as important as the displacement/rotation channels. Just need to make sure whatever option we look into has the least data loss through it's transmission.
If you were to "turn off" the amplifier on the MTS system, it's easier for us to recommend a card that has the accuracy needed. The smaller the voltage range the more accurate the measurement is.
In example if you were to use the PCI-6225 you can reach this kind of accuracy in the following range:
Minimum Voltage Range-200mV, 200mV
Minimum Voltage Range Accuracy112µV
The kind of sensors you are reading from, load and torque cells, lvdts, encoders, they have a small voltage range. And with an ADC with a 16 bit resolution you can detect a change of 6.1µV.
Another option would be the PCI-6255, it's has a smaller range but has a higher accuracy.
Minimum Voltage Range-100mV, 100mV
Minimum Voltage Range Accuracy 52µV
I can't turn it off, but I can turn it down. The native voltage is ± 10 V, multiplied by a gain, which can be set from 0.01 to 100 I believe. So I think I can go as low as ± 0.1 V full scale output. I'd have to mess around with it to be sure.
With either of those two cards then, I'd just need the bnc's wired into a connector block or blocks, then through the cable to the card?
Do either of these cards have vi files that are associated with them that are already setup to read and record from all channels? I'm trying to imagine programming 80 channels in a block diagram... Head is already spinning...
If you manage to turn the gain down and use the range of -100mV to 100mV with the PCI-6255 you would need to terminal blocks SCB-68, this are screwable terminals. You could use the BNC-2090 but you only have 22 BNC terminals per block. So in order to access all the channels you would need 2 SCB-678 terminal blocks.