# Data measuring interface

I have an hardware related question.

I want to create a measurement set-up so that I can record data for DSP analysis. When searching around I see I have a few different options. The ones I have found are:

• Data acquisition box / interface
• Logic analyzer
• Scope
• Soundcard (have specific input type (XLR/ TRS-Jack) )

From DSP perspective what are the differences between these types of measuring devices? Specially the difference between a DAQ and a logic analyser?

As Questioned in the comments: what are the parameters i want to measure. Here is the list for now(witch can change later on):

• Torque
• Acceleration(vibration)
• (velocity)
• Force
• if possible Ammeter
• different switches for safety sensors(just low and high over time)
• some pulse generators

I'm not sure what the bandwidth is of every signal. But i assume that the maximum bandwidth is from the acceleration sensors. I assume that the bandwidth is f_max = 10kHz so f_sampling = 25 or 30 kHz.

• so, what data? Without that info, you can't get a precise answer. Signals/data are everywhere, and it kind of makes a difference whether you're watching the changes in temperature on noon over the year, or the number of photons hitting a sensor within 10 femtoseconds.... – Marcus Müller Sep 8 '17 at 20:33
• edit my question – Jan-Bert Sep 9 '17 at 6:15
• So, what are the speeds with which these things can change? – Marcus Müller Sep 9 '17 at 7:36
• don't exactly know yet... let's say for vibration stuff f_max = 10kHz so f_sampling = 25 or 30 kHz but not sure if that is relevant for what the differences are. It looks for me more within a chosen recorder/ device what type do i need (#channels, sample frequency etc). If it is important make it part of the answer... – Jan-Bert Sep 9 '17 at 10:53
• Well, that's very important info! include it in your question!!! Better give too much than too little info. So yes, if in doubt, everything is relevant. – Marcus Müller Sep 9 '17 at 10:54

## 1 Answer

Eventhough it's not fully clear what sort of an environment you are referring to by the measurement set-up, in the most broadest sense of the term you need either a data acquisition interface or a sound card for the cheapest semi-alternative.

A data acquisition interface to a PC is what you mainly need. There are a bunch of alternatives. You must set your requirements (data rate, #channels, bit depths, ADC linearity, SNR etc.) to get the optimal match for the price. Note that the software interface to the acquisition hardware is another concern that makes big functional differences in the end.

The cheapest alternative to a professional data acquisition hardware can be a PC audio soundcard. They will record AC coupled and distorted signals. So no DC is captured unles you modify (if possible) by shorting the soundcard's ADC chip's input-DC blocking caps. There are a number of soundcard capturing software which also simulate an oscilloscope as well. Most typical PC (laptop) sound cards do provide 16 bits, 2 ch, 96 kHz sampling these days.

A logic analyser is almost useless from a DSP point fo view. Logic analysers are used for digital electronics such as logic gates, microprocessors, interface protocols etc. to analyse their bits, high and low values, ones and zeros.

An oscilloscope is again useful mainly for analog electronics diagnosis purposes. It's an indispensible hardware tool for any hardware project, but not exclusively required for data capturing, unless you want to observe in real-time what you are capturing.

• edit my question – Jan-Bert Sep 9 '17 at 6:15
• answer needs no edit but – Fat32 Sep 9 '17 at 9:04