Question Suggestions for DAQ for Engineering Fluids Lab?

[Thunder Chicken]

I teach engineering at a local college, and I've been tasked to upgrade the current DAQ equipment in our fluid dynamics lab. The current proprietary system only works with sensors sold by the manufacturer, and the equipment quality is poor and they will require an expensive software licensing scheme if we upgrade. We're tired of throwing good money after bad at them.

Our needs are pretty basic. In general, we need pressure, temperature, force, voltage, current logging capability. Sampling rate is not critical (1 Hz would be adequate) and a minimum of 4 channels, though more would be nice, especially if we start designing more interesting lab activities.

I am not terribly knowledgeable about DAQ systems except for general concepts, but I can code and I'm happy to climb the learning curve for the interface. Something that doesn't lock us into a proprietary software licensing agreement would be preferred. Something that can cope with OS upgrades for the forseeable future would be necessary.

Can anyone suggest a DAQ hardware/software combo that might be suitable for this sort of lab? The computers are Windows 7 machines. I've heard about Arduino boards but don't know much about how they are used in this application.

Thanks to all!

 

[Urwumpe]

Which digital resolution do you need?

 

[kamaz]

Our needs are pretty basic. In general, we need pressure, temperature, force, voltage, current logging capability. Sampling rate is not critical (1 Hz would be adequate) and a minimum of 4 channels, though more would be nice, especially if we start designing more interesting lab activities.

Assuming that you have transducers, I'd have a look at Meilhaus Redlab:

http://www.meilhaus.de/en/products/usb-mobile-data-acquisition/?user_produkte[PR]=89&user_produkte[BTN]=bestellinfo&cHash=ffaab1f9d6

You can buy from the directly or through Newark/Farnell/element14.

I've heard about Arduino boards but don't know much about how they are used in this application.

Condition your signals to be between 0 and 1.1V and connect to A0-A5 inputs on the Arduino board, and run this code:

void setup() {
  Serial.begin(9600);
  analogReference(INTERNAL); // 1.1V built-in reference voltage
}

void loop() {
  for (int ch=0; ch<5; ch++) {
    int adc = analogRead(ch);
    float voltage = 1.1*adc/1023; // 10 bits ADC, full scale is 1.1V
    Serial.print(voltage, 4); // prints float with 4 significant digits
    Serial.print(" ");
  }
  Serial.println();
  delay(1000); // wait 1000ms
}

http://arduino.cc/en/Reference/analogRead
http://arduino.cc/en/Reference/AnalogReference

Also, last summer I was teaching a class on using Arduinos for DAQ / sensor networks. PM me if you want lab notes and reference code.

 

[Thunder Chicken]

Thanks Kamaz! I have some reading to do. I'll send you a PM - those notes would be a great help. I need some basic introduction to all this. Thanks!

 

[kamaz]

One thing to note about Arduinos -- if they are powered from USB, then the +5V supply line has a lot of noise (it's taken from the computer directly).

In measurement applications, I'd recommend running them from an external +9V supply of decent quality. And probably use an external reference voltage chip -- Analog Devices makes some good ones.



---------- Post added at 03:09 AM ---------- Previous post was at 03:01 AM ----------

Also, this allows you to use Arduino as a DAQ board with LabView: http://sine.ni.com/nips/cds/view/p/lang/pl/nid/209835

 

[Thunder Chicken]

One thing to note about Arduinos -- if they are powered from USB, then the +5V supply line has a lot of noise (it's taken from the computer directly).

In measurement applications, I'd recommend running them from an external +9V supply of decent quality.

Kamaz - I received your PM. Thanks!

The current hardware is USB powered and I have noticed the noise from that. It's a nuisance but not fatal.

Any suggestion on a board? I am thinking of getting a board for my own personal use and tinkering with it until I am confortable with how it all works before trying anything at school. There is an Arduino starter kit, but it sounds a bit like an old Heathkit and I'm not sure how helpful that will be for what I am trying to do.

I have a PhD in mechanical engineering, smart in a way, but am somewhat of a rookie with these sorts of things. When I was in industry we always had an electrical engineer who was the DAQ guru that just made this stuff happen. Now *I* am the guy that needs to make it happen.

 

[kamaz]

Uno boards are the current generation. The design is open sourced, so you can probably find cheaper knock-offs if you look around.

The board itself is pretty difficult to damage, but it's much easier to kill the microcontroller itself. Fortunately, they are quite cheap (ATMEGA328). However, you will also need SPI programmer (AVR ISP Mk II) to reflash the bootloader after you replace the chip. Still, the programmer plus replacement chips will be much cheaper than replacement boards

You will also need the breadboard, wires and basic components -- either get them separately, or as a kit. Does not matter. The kit is simpler, but then original Arduino stuff tends to be overpriced

I would start with connecting potentiometer to the board and writing a simple program which reads the potentiometer and send the result over USB. Just like the one I wrote above.

The hardest part is going to be the analog conditioning circuit -- in general you'll need some op-amps (LM324 will do for then start; at the later stage you should move to rail-to-rail CMOS op-amps, but they are more expensive) and a book on analog electronics. Fortunately, op-amp based design is quite simple.

For integrating the final circuit with Arduino, you solder it together on ProtoShield and plug that into Uno:

http://www.adafruit.com/products/51
http://www.adafruit.com/products/196