Help selecting DAQ/signal processing for school project

[jcoffi2]

Hi, I am in charge of finding all of the necessary DAQ equipment my group needs for a school project. We are setting up a test apparatus with various sensors including two type K thermocouples, a pressure transducer, a shaft angle encoder, and a load cell. We had our eye on the NI-USB-6210 DAQ, but we are not set on this if you can recommend a better one for our application. I need to know if we need any type of signal processing hardware such as amplifiers/attenuators, filters, etc to make this work with LabView. I have been doing some research, but this is my first time setting up a DAQ system and I'm starting to get really confused about what we would actually need for this setup. I have included pdf files of the data sheets for the encoder and load cell. This is the pressure transducer we selected: Pressure Transducer. And here are the thermocouples: type K thermocouple. There are two encoders, but we will only be using one or the other. Thank you so much for any help. We are trying to figure all of this out as soon as posssible and are on a really tight schedule.

[jcoffi2]

Please?

[FuManWho]

Hi jcoffi2,

There are a few questions that go along with choosing hardware:

1. What are the accuracies and the resolutions of the measurements you want?

The 6212 has a resolution of 16 bits and absolute accuracy of 2.69mV
2. Would you like simultaneous sampling?
Your curent device is not simultaneous sampling and will use a multiplexer so it is not true simultaneous sampling.

3. What signal conditioning do you need?

The pressure transducer has a voltage range of 12v to 36v where the device accepts 10V. I did not look at the rest but please make sure that the output is within the range of the DAQ.

4. What is the frequency of measurements?

The aggregate frequency is 250KS/s

5. What is the memory size needed?
The fifo size is 4095 samples.

I found this information in the specification sheet. I recommend seeing the output of each sensor and looking at the specification sheet of some of the DAQ devices you are interested in.

[jcoffi2]

Thanks for the help. I don't know much at all abou this kind of stuff so bear with me.

1. What are the accuracies and the resolutions of the measurements you want?

The 6212 has a resolution of 16 bits and absolute accuracy of 2.69mV

I guess that's good enough?

2. Would you like simultaneous sampling?
Your curent device is not simultaneous sampling and will use a multiplexer so it is not true simultaneous sampling.

Yes, we need to be able to read 4 of the sensors at once. For one of our tests, we need to read the thermocouples, encoder, and load cell at once, and for the other test we need to be able to read the thermocouples, encoder, and pressure transducer at once. I'm not sure of the difference of true simultaneous and multiplexer though. 

3. What signal conditioning do you need?

The pressure transducer has a voltage range of 12v to 36v where the device accepts 10V. I did not look at the rest but please make sure that the output is within the range of the DAQ.

That's one of the things I don't know. So if we go with that transducer, we need some sort of conditioning to get it into that range, but what kind of conditioning will do that?

4. What is the frequency of measurements?

The aggregate frequency is 250KS/s

That should be fine for our application.

5. What is the memory size needed?
The fifo size is 4095 samples.

I don't know what this means haha sorry.

I'm going to look at it some more and really appreciate the help.

[jcoffi2]

Also, what does it mean when the output is listed as amperage? I've seen some listed as amps, some as volts, and some as both.

[FuManWho]

True simultaneous sampling means you can sample each sensor at the same time because you have one analog to digital converter per channel. When multiplexing you have one analog to digal convert which is accessed via a multiplexer which switches through the channel. This introduces a bit of lag between the sensor measurements. The time in between measurements will be approximately 4-7 microseconds.

The simultaneous sampling cards are a bit more expensive though.

This resource goes over some signal conditioning. I would highly recommend researching your options when you decide what signal conditioning you want.

The device you are looking at has a max amperage of +-20mA. Make sure the output of the sensors do not go over this.