Seeking electronic testing equipment suggestions

[Jerran]

Im looking to get some suggestions on what to look for in test equipment and what equipment would be most beneficial in the areas Im interested in.

First off my main focus has been on pic programming, RF communications(data and voice), audio filtering, and basic robotics. Atm all Ive really got is a digital multimeter from radioshack and a 12 volt dc power supply.

Ive used scopes and function generators in college so I understand their basic function. ID like to know what to look for when purchasing oscilloscopes, function generators, possible better power supplies, and/or frequency counters. Obviously the higher modeled units have more versatility but how much would be required from each type of equipment for the type of projects I do?

Oscilloscopes:
>Single or duel trace?
In class we had duel trace but never used that option in class, what is the advantage of displaying a duel trace? Phase shift is the only thing that comes to mind offhand.
>30 60 100 Mhz
What frequency would be optimal for the types of projects Im interested in? What exactly is the advantage of having a 100 mhz over a 30.
>Are their any options/attachments I should purchase with it?

Function Generators:
>Frequency
Ive seen units from 3 to 20 Mhz. What frequency would be required for the project types I listed, more is always better then less but what would be considered overkill.
>Are their any specific features I should make sure a model has?

Power Supplies:
>Ill definently get a unit with a higher output voltage but are their any options/features I should look for in a unit?
>We had current limiting units in class, is this option ever needed?
Every project we did we turned that function off, our models had short-circuit protection so I guess it wasnt required.

Frequency Counter:
Ive never used one before, Id imagine from their high frequency rate they can be used on RF projects.
>What options should I look for in a unit and is a frequency counter even required for more advanced projects in RF/audio applications?

Thanks in advance.

 

[bmcculla]

For Scopes dual trace is definately useful. Any time one signal triggers another signal the dual trace lets you see both and their relationship. As for the bandwidth: 30MHz is probably fine. This is just the greatest frequency signal that you will be able to see acurately on the scope.

For function generators: Having higher frequencies is useful but my 2MHz generator works fairly well for what I do. Make sure you get one that lets you vary duty cycle. Thie will let you test PWM circuits and counter timers.

Power Supplies: Having a current limiting supply is nice. It keeps you form blowing up thing when you have a short. You can also charge batteries and other things that require a current source.

I've never used a frequency counter.

Brent

 

[Asjad]

test equipment

Dear bmculla,

When I boought my oscilloscpe I found out that could of saved 50%
if I looked at:

Ebay - Test equipment section

Goverment surplus retailers - There are many of these on the internet!!!

Army surplus

If you want to save a bob, try the above sources.

As long as you buy a reputable make of test equipment it should last
you a long time!!

Hope this helps!!

 

[Jerran]

Cool thanks for the replies. What brand/companies of scopes make a quality product?

 

[Asjad]

Names

Try to get oscilloscopes with built in signal generator!!!!!

Scopes - Gould, Tetnotronix, Philips - 20-30Mhz

Power supplies - get dual supply with current sensing

Search around for good reputable manufacrturers on the internet


Hope this helps!!

 

[stevez]

I am far from being the expert here but find my DVM to be a very important tool. I like to be able to measure things like AC riding along with DC - but the AC part only. I like the true RMS function too - resolution may be important to you (number of counts or samples per second). I have one low cost DVM that has an autoranging function - that I don't like. It decides what scale and whether AC or DC so I can't measure something like power supply ripple so watch out for that. So far I am happy with a recent purchase from Radio Shack - frequency meter to 10 mHz is particularly nice - very accurate too. One feature that I've not used a great deal is the RS-232 interface which is available on some. Seems like it would be nice for longer term monitoring.

I think they make modules or plug-ins for some scopes that allow it to function as a DVM. I know in this area there is a lot of reasonably priced Tektronix equipment - a generation or two old but still quite serviceable. I tend to like to keep multiple instruments around rather than rely on one large item that does everything. May be old fashioned but electronics is only my hobby.

 

[Dean Huster]

Test Equipment

The spelling is "Tektronix" and is considered to be the ultimate brand in oscilloscopes. Don't let anyone try to tell you that a digital scope is the only way to go. The older analog scopes are just as useful today as they were in 1960 and you can get top-quality, lab-grade plug-in analog scopes or high-end service scopes for far less than you'd pay for a "bottom feeder" digital scope. And I definitely caution against buying a new scope, especially one made in Asia. Asian scopes, especially inexpensive ones from China and Korea rarely come with decent manuals, usually have no schematics or calibration information and have a horrible service structure if any. If you have the CRT go out on a Hipsung brand scope while it's under warranty, you'll probably be sucking air with regards to ever getting it fixed. If you're lucky, the deal will refund your money or swap you out with a new scope ... but I doubt it. Don't worry about finding parts for that used Tektronix 7704A or 465. There were so many of them made (like VW Beetles) that you can always find "hanger queens" to rob for parts.

Dual trace is not an option. It's necessary, not only for viewing phase shift, but for looking at any timing relationships, especially in digital circuits where you seem to be putting some of your emphasis. A bandwidth that's at least four times higher than the fastest digital frequency you'll be viewing should be plenty. You can get 100MHz, 200MHz and higher bandwidths on ebay for a song.

Low end function generators will likely suffice for most of your needs. The ability to have variable symmetry is a plus for the PWM work as one poster mentioned. And if you work with audio filters, a function generator with built-in sweep would be great. But you may be able to buy two low-cost generators for less than one with sweep. You can always use the triangle output of one to drive the VCF of an other to provide sweep.

If you're doing precision, low-distortion audio work, a function generator will be useful only for general troubleshooting, for its sine wave output will have distortion in the 2-3% range or more. The best Tektronix function generators (e.g., the FG502 or FG504) may get as low as 0.3%, but if you're using a distortion analyzer, you absolutely must have a low distortion sine wave to work with. This means an audio oscillator and not a function generator. The old Hewlett-Packard 200CD isn't bad as are newer versions of the "200" series.

You may find that the emphasis on variable voltage power supplies, especially ones that will go all the way down to zero volts, to be unwarranted. If you do digital work, you'll usually just use a fixed 5v, 3.3v or 3.0 v supply; if doing analog work, you'll usually just use a fixed ±12v or some such supply. The variable supplies are mostly for learning situations where you have an experiment where you plot diode voltage drop against forward current and such things. Now, current limiting can be very handy, especially if you have a habit if installing semiconductors backward!

Dean