Several questions about cDAQ and their modules

[Battousai]

Hi, i´m sorry about my english, but i dont know to write very well.

I need configurated a Data signal Adquisition and i choose the cDAQ modules:

NI 9229 to proximity probe
NI 9233 to accelerometes
NI 9237 to strain gages

I have many questions about the boards and the global system.

1. What is the difference between overvoltage protection and Isolation??
2. How i can synchronize the three tarjets??? Some of then need i some particular position???
3. How i can synchronize the input of this boards??? Th three NI 99xx have differents input delay

Respect Ni 9229

4 This targets have screw terminals input. How i can connect a SMB input?
5 What is NI 9971 and NI 9976?? so that they serve?
6 to Specifications... is correct say the maximun transient voltage is 250 V?

Respect NI 9233

7 Why does not have values to Isolation???

Respect NI 9237

8 Can i connect different types of bridge in the channels??? For example. Ch0------->Full bridge;  Ch1, Ch2----> Half bridge and simultaneous adcquired?
9 Why half and full bridge are "internal"? Why quarter bridge are external? ¿can i measured quarter bridge?
10 What are te NI 9942-9944-9945 and 9949??? so that they serve??

thanks so much to any help.

[Battousai]

Nobody can help me???

[KyleBryson]

Hi Battousai,

I agree with the Spanish-language reply to your post that you will find many answers to your questions in the documentation for these products and across Developer Zone.  For example, here is a white paper that discusses isolation:

http://zone.ni.com/devzone/cda/tut/p/id/3546

The NI 9233 does not have isolation, as documented in the specifications section of its manual.

Please continue to post (in either language) if you have questions about isolation and overvoltage protection after reading the white paper above.  This important for making sure that your system is safe and does not damage your hardware.

Regards,
Kyle

[Battousai]

Thanks for your answer.

im read the document, was be very useful. I dont understand why the 9233 doesnt have isolation. What happens if a transient voltage occur???

About the other questions, how can i compensated the input delay of the targets... all are differents.

Im apreciated if anyone can help with my questions.

Thanks

[KyleBryson]

Battousai,

Modules are designed with different isolation specifications to meet different application needs and require tradeoffs against physical constraints and other specifications, and the 9233 is one module that does not have isolation.  It does protect from overvoltage to +30 V, and somewhere between -6 V and -30 V in the negative direction depending on your source.  A transient voltage on your input outside of this range may damage the device.

Since all of the input delays of the modules are specified in their manual, you should be able to figure out their relationship.  You can manipulate the arrays of data that are acquired to remove or shift samples to line up more closely in time.  There is a short example of a way to do this using the waveform datatype here:

http://digital.ni.com/public.nsf/allkb/CAE12AA9BCAA51A48625722C004866F8

Without knowing your application, it will be difficult to recommend a more specific way of aligning the data, but any solution will rely on the input delays specified in each module manual.

Regards,
Kyle

[Logan_K]

I was checking the forum and noticed that several of your questions went unanswered. I will answer some of the questions that Kyle didn't get to...

4. This targets have screw terminals input. How i can connect a SMB input?
You will need to convert your SMB connector into screw terminals. NI does not have a specific solution for this.

5. What is NI 9971 and NI 9976?? so that they serve?
The 9971 is a strain relief and high voltage protection backshell that attaches over the screw-terminal connectors. The 9971 connectors comes with zip-ties that can be used for tying down the two wires for strain relief. The 9976 is a replacement kit for the screw-terminal combicon connectors that come with the module.

6. to Specifications... is correct say the maximun transient voltage is 250 V?
This depends on the nature of the transient voltage - and it involves understanding the difference between overvoltage protection and isolation. In the case of the 9229, each channel can be referenced to a different voltage level independent of the other channels and the voltage difference between those channels can be as high as 250V. An example of isolation is that you can measure 5V by supplying 150V to the + terminal and 145V to the - terminal - this works because the module uses 145V as the ground reference. When the module claims that it is isolated up to 250V, this just means that largest voltage that can be safely supplied to either + or - is 250V. We test this condition by supplying 250V on both the + and - terminals at the same time - you will damage the module if you supply 250V to the + terminal and 0V to the - terminal.

A single channel can have a maximum of 100V supplied differentially across the + and - terminals (100V on the + terminal and 0V on the - terminal): this is Overvoltage Protection. The module is not designed to handle differential voltage spikes above 100V.

8. Can i connect different types of bridge in the channels??? For example. Ch0------->Full bridge;  Ch1, Ch2----> Half bridge and simultaneous adcquired?
Yes.

9. Why half and full bridge are "internal"? Why quarter bridge are external? ¿can i measured quarter bridge?
For Quarter Bridge, you need a Quarter Bridge completion resistor that matches the resistance of the strain gauge you are using.

10. What are te NI 9942-9944-9945 and 9949??? so that they serve??
The 9944 and 9945 are adapters for quarter bridge strain gauges that have built in quarter bridge completion resistors.
The 9949 is just a 10-pin screw terminal adapter for the 10-pins of a RJ-50 cable.
The 9942 is a connector that you can use if you want to use an external excitation source for your strain gauges instead of the built-in excitation of the 9237.

Regards,
Logan

[Battousai]

Thanks a lot.

I think  understand all.

Again, Tx