Advise about DAQ..experts please get involved

[Bildavid]

Hi labviewers

I have designed and implemented an ECG amplifier . I was trying to send this signal into the computer via RS-232 but i did not succeed . I have read in the forum that using DAQ is much better for my purpose. 

KINDLY I am requesting experts to answer the following please :

1 - the circuit that i have implemented uses a microcontroller to digitize  the signal and send it to the serial port via max232 . IN case i want the DAQ to be involved in my project , shall i get rid of the microcontroller and the max232 part and supply the DAQ only with analogue signal ????

2 - let us say i bought the device .which costs about 600$ . what drivers should be installed on the PC ???

3 - what is the best DAQ in your point of view ( based on your experiments ) that should be involved in this project ???

4 - can you give hints ? can you give ideas ? anything related to the device please ?

[GerdW]

Hi Bill,

your questions are rather vague...

1) In case you want to use DAQ hardware you don't need RS232 anymore...

2) When you have the hardware you should also got some drivers to install. Why don't you tell the type/manufacturer of the DAQ hardware?
3) That's a stupid question. You have to tell requirements first before deciding which hardware to buy...

4) Write down your requirements...

[Bildavid]

Hi GerdW ,

I beg your pardon but this is the first time i think of using the DAQ . I was having hard time trying to filter out the ECG signal that I am acquiring through the serial port .I did everything withing my power but nothing revealed untill i was told that using RS-232 is useless for such an application . that is why i decided to have  a DAQ that takes the analogue signal , then digitize and send to the pc with labview running on it hoping that I can attain the best ECG signal i can . 

 I also wanted to know more about the sampling rate of the DAQ . 

Thank you .

[GerdW]

Hi Bill,

it does not work that way!

You have to define requirements, then you will look for suitable DAQ devices!

[Bildavid]

Hi GerdW !

what do you mean by requirements ? do you mean the input and outputs for the card itself and how many analogue and / or digital inputs and outputs it has ?

I am totally new to the DAQ . I posted here to get some info .

Thank you .

[GerdW]

Hi Bill,

you already mentioned "sample rate"...

- number of analogue and digital inputs/outputs

- sampling rate

- measurement ranges for analogue channels

- voltage levels for digital channels

- any special functions (like triggering, counter, pulse generation, ...)

- much more...

You have to define your requirements!

[crossrulz]

As Gerd said, we need to know what you are trying to measure (voltage range, sample rate) before we can make any suggestions.  If you know some general specs, NI has a decent DAQ selection tool (see here).

[Yamaeda]

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@Bildavid wrote:

what do you mean by requirements ? do you mean the input and outputs for the card itself and how many analogue and / or digital inputs and outputs it has ?

To determine which card is needed you must describe how you're measureing, how you plan to measure it, how exact it needs to be and how often.

It sounds, at a glance, like you want to measure a single voltage in normal low voltage environment (0-10V) at a low speed (max 1 kHz), how accurate would that assumption be?

E.g. http://sine.ni.com/nips/cds/view/p/lang/sv/nid/201986 might be a place to start looking? Or would you prefer a PCI-card?

/Y

[Bildavid]

Dear Yamaeda

First thank you for the reply .

no . the signal i m trying to measure is in the range of 75 microvolts . ( IT is an ecg signal takes from leats attached to the amplifier circuit )

One more thing, I guess i want the DAQ to have a high clock rate  for the A/D (sampling frequency good enough )

Thank you .

[GerdW]

Hi Bill,

so you mentioned your first requirement: measuring a voltage signal with 0...100µV range.

You still have to define more requirements!

- What is a "high clock rate"? I assume you mean the term sample rate... Is 10kHz high enough or do you need 10MHz sample rate?

- What kind of resolution/accuracy is needed? You may use a simple USB6008 to measure your voltage, but the accuracy of that little box is way to low for your needs (I assume)...

DEFINE ALL OF YOUR REQUIREMENTS!