My take on the UT81
-------------------
Since releaseing this package, I've had a few people ask me what I think
of the UT81. Having had it for a number of months, and used it a fair bit,
This is my opinion:

Short:

You might want to think of it as pretty decent multimeter which happens to
have some graphical display capability. If thats what you are looking for,
it is worth the price, and you will probably be happy with it (I am).

If you are looking for a full-service oscilloscope to replace a good bench
scope, and plan on using this capability a lot, then you will probably be
disappointed.

If you rarely need a scope, and can live with it's limitatins, it does
make a passable scope "in a pinch" (and comes with a nice meter).


Long:

The good:

It's very inexpensive for a "scopemeter" - i've seen it between $100-$150.
You should keep this in mind when considering "The bad" - you really can't
expect a top of the line scope in this price range.

Seems well made and fairly rugged.

It makes a pretty nice meter - 3-3/4 digits, and when in "meter" mode the
display is quite large and very easy to read. Seems reasonably accurate.

It's physically large for a meter, but not unreasonably so - and it does
come with a decent storage case.

It does have graphical display, and can serve as a scope "in a pinch".

"Auto" setup mode seems to work reasonably well (if a bit slow), and usually
gets you to where you can "see something".

It's battery powered - this makes it GREAT for looking at differentials
on high voltage lines or any other situation where you really don't want
the scope to be anywhere near ground.

It has an isolated serial port - comes with USB cable, and easy to build an
RS-232 one - handy if you want to automatically capture data from the meter.


The bad:

It's mildly annoying that it always defaults to "Scope mode" when powering-
on or switching to a new function.. it makes a better meter than it does a
scope.

It's not a fast scope - Mine is a UT81B, which is rated for 8Mhz, not
terribly fast, but still useful for many things. There is also a UT81A
which is rated for 2Mhz, which I would avoid unless you are only doing
audio work.

It's not a terribly easy to use scope - Timebase, Range, offsets, trigger
level etc. are on buttons which move values up/down - and there is a
noticable lag responding to the buttons which makes "trial and error"
adjustment taxing. I find it can be quite tricky to get a good display of
anything but a simple signal. If I have the choice, I prefer to use one
of my bench scopes which are much easier to set up.
But with a bit of work, you can usually see what you need to see.

It's only a single-channel scope, and there is no external trigger option.
This limits it usefulness to examination of single signals and waveforms.

It uses test-lead inputs. Great for a meter, not so great for a scope at
higher frequencies - it does come with a BNC<>Test-Lead adapter, however
it is of low-quality (even the BNC jack is plastic with just "fingers"
inside to make connection), and doesn't mate well with real scope probes.

It does have some "bugs":

"SHOT" (single-shot) trigger works by tripping "HOLD" at the end of the
capture. This works well, except that you can't make any adjustments when
it is in HOLD mode - so if you are using single-shot capture in the
presence of a signal (which keeps tripping the meter and putting it in
HOLD), you have to change to another trigger mode to adjust the capture
settings. This can be quite annoying when you are trying to set up to
capture an infrequent and irregular event.

Triggering does not work with a timebase higher than 100ms per division.
At 200ms and above the meter just keeps going (overwriting the previous
capture). This makes "SHOT" capture of slow events useless (which is too
bad because capturing images of very low frequency events is something
this meter would be otherwise well suited for).

The "AC" setting in scope mode seems to have no effect on the display,
which means you can't use it to view little AC signals superimposed on
bigger DC ones without an external blocking capacitor (such as looking
at tones on a phone line which what I was doing when I discovered this).



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