Logic Analyzer Help~

[MrAl]

Hi again,


If speed and input impedance are not issues then you can use lots of different types of opto couplers.

They make the type with a bridge rectifier input that include the dc output (for filtering).
They also make a type with two input LEDs, wired in inverse parallel, to make sensing AC
a little easier although the output would be a pulsing wave unless it was filtered.
Avago makes lots of different types that include those.

[dtief]

I've had good luck with this one:
http://www.pctestinstruments.com/index.htm

It is almost $400., but I had to analyze a DSP and other microcomputers.

[Lenp]

Ron,
That's a really generous offer, I am tempted, but the laptops available have no serial ports. I perhaps could use a USB/serial dongle but I've had some bad success in the past with some of those. Our shop systems have serial ports but the acid test is in the hostile nvironment!

Looking at the Dataq package price I may just order a USB unit and be done with it. I am interested in the VB codes if that offer still stands. Do you know if the basic software from Dataq will support multiple USB units? Do you have any different software suggestions.

Again thanks,

Len

[reloadron]

Hi Ya Lemp

OK it has been an afternoon of some discovery. Using my Windows XP workstation I connected a DI-148 and a DI-158 using USB. Now the way things work is the DATAQ software includes an instrument Hardware Manager where you choose a device connected to the system to run. I can't seem to get two instances of the software for a specific unit to run. I never really tried it and this may me me missing something.

Now I don't know how liberal your company is with little projects but figure for about $50 the cost of a basic DI-148 eight channel single ended starter kit it is a small investment. Now if that works out for you another unit I use extensively outside the starter kit family is the DI-710. I like that for small work in that it offers up either 8 channels (differential input) or 16 channels (single ended) input. Additionally it offers more but that is the basic analog input channels. That is about a $500 unit.

Writing programs for these things is not that difficult (even for me). Therefore I would be happy to help you out in that area.

Next, and again depending on budget, you will need to figure out each signal you want to look at and then worry about signal conditioning.

Oh yeah, before I forget, the people at DATAQ are very helpful.

Ron

Ron

[Lenp]

Ron,

Thanks again for your input. Are you using the basic Dataq software, or the upgrade?

I can't seem to get two instances of the software for a specific unit to run. I never really tried it and this may me me missing something.

What is meant by the quote above?

I reviewed much of the Dataq data and have a few questions!
Can two units be connected simultaneously to provide more channels?
How many channels will the software support at the same time, same screen?
In the 148U there are 8 analog and 6 digital channels. Does that mean there are 14 channels, or are some chanels shared?

As for the conditionng I'll pull each channel down with a resistor then use a opto-isolator transistor output powered from the USB 5V rail to pull it up to show activity. Simple 0 to 5V (high=on) swings. Each opto-isolator's LED will have a bridge rectifier input, a minimal filter cap for 60 hz and scaling resistors as necessary for the input voltage. Using this scheme, it will work on AC/DC and because of the bridge, polarity will not matter. Another plus is that there is no common connection shared by the testing inputs even though the analyzer has a common for all its input channels.

I would like to incorporate continuity on the testing input side as an option, but without using batteries to drive the LED on each channel isolator, I don't see any way to have the same isolation feature on the testing inputs.

It looks like I'll order the Dataq starter kit, possibly tomorow, and then start cobbling together the conditioning board. I'm not sure yet if I want to use rotary switches or jumpers for the voltage selection. Based on it's small size I may enclose it in another enclosure and use a D-25 connector for the I/O to simplify connecting it the interface, or to a lead jungle for other uses. With luck I might parlay this critter from a $50 investment to a $1000 project If it doesn't work out then I guess it will be great for it's intended uses!

Len

[reloadron]

Hi Ya Lemp

I wanted to be 100% sure so I spoke with Shawn at DATAQ. Yes, you can run two instances of the software looking at two seperate modules. With two modules connected (Example 2 EA. DI-148) they will both show in the device manager when the software is launched. That holds true for the "lite" software too as in WinDaq Lite. On the same screen it just means each window of 8 channels will be smaller.

In the 148U there are 8 analog and 6 digital channels. Does that mean there are 14 channels, or are some chanels shared?

Yes there are 14 channels, what it actually means is that there are 8 single ended analog input channels (shared common) and then there are 6 digital channels. The software allows setup of those channels individually as DI (Digital In) or DO (Digital Out). The same can be accomplished when writing code for the units.

There are other companies that make these things but I started with and have remained with DATAQ simply for convenience. They are in the Akron / Canton area and I am in Cleveland.

Maybe this weekend I put something together for the DI-148 that will show what it can do from a code point.

Ron

[Lenp]

Ron,
Amazing as it may be I located a Dataq DI-194 rev G. stuffed away and forgotten about!
It's a bare board, serial I/O, 4 analog and 3 digital channels.
I have the manual and software, as well as newer software I downloaded from Dataq.

After getting it up and running I think it may work for me, but, I'm not sure about it's usefullness with their free 'Lite' software. The sampling rate is way too slow for most logic work. I was able to change the serial port baud rate and got the unit to sample at 480 instead of the default 240 but that still is slow. Maybe the gimmick here is to get you to upgrade to the faster software. If that's the case, it puts it dollar wise, in the same league with everyone else!

Another oddity, I strapped the 4 analog channels together and used a analog input (music). The display was different on each channel, not skewed in time as you might expect, but the waveforms were somewhat different. The same test with a square wave was better displayed, but was limited in the upper frequency before the waveform trashed because of the scan rate.

Maybe the newer USB units are better? (software still caps at 240 without an upgrade though)

What's your opinion? Am I missing something here?

Len