Favorite multimeter died, looking for a replacement - Page 1
Forum section: electronics / testgear

author: halfwalker
author_rank: Contributor
timestamp: October 06, 2013, 03:28:34 am
content: I've had an Extech 381270 Multiscope for a bunch of years now, and it's been a workhorse. Great autoranging, lots of modes, and does a nice little oscilloscope display in a very portable package. It sat on the shelf for about 10 months while I was away, and of course when I got back the batteries were completely dead.Replaced them, and all seemed well, until I tried a measurement. Resistance was all over the place. Ran self-tests, all come back as good. Test 12V DC, doesn't see it, just wanders around below 1V. Test 120V AC from the wall, it bounces from 30V to 90V to OVER to 0V and all over the place. Dang blast it. Fuses are all good, and a cursory glance over the pcbs doesn't show any obvious culprits. I checked on the Extech site, and they don't even list the damn thing any moreSo, given that it's probably casters-up, I'm going to be looking for a replacement. I definitely like the scope function, that's come in SO handy on many occasions. Especially since my main scopes are older HP/Agilent 30lb beasts they're a little touch to maneuver into cars and other small spaces.Any picks to check out ? How about ones to stay the <bleep> away from ?

author: Wytnucls
author_rank: Super Contributor
timestamp: October 06, 2013, 03:45:11 am
content: CEM and UNI-T make a similar instrument.http://www.cem-instruments.com/en/pro/pro-824.htmlhttp://www.uni-trend.com/UT81B.htmlNo idea if these are good value or not, but there are reviews on the internet.

author: retiredcaps
author_rank: Super Contributor
timestamp: October 06, 2013, 06:59:37 am
content: Did you check see if the input resistance is around 10M ohm on the Extech?Also, are there any signs of battery leakage on the pcb?

author: halfwalker
author_rank: Contributor
timestamp: October 09, 2013, 03:52:29 pm
content: Check inputs - doesn't register at all on my other meter, just shows OVER. PCB looks OK - the battery contacts had a little bit f green residue on them, but that was easily brushed away and they look fine.Checking resistance on crossed probes, it wanders from 20-400ohms or so.Heard back from Extech ... 2 separate emails.The cost for a repair for this model is $175.00, plus shipping and any applicable taxes. This is a flat rate as long as the unit can be repaired. However, because this is a discontinued model there is a good chance we will not have the parts for repair. If this is the case, we will not charge you for the cost of repair.and the other one wasI've talked with our Repair department and we do not have any parts to replace any parts that are defective, as this instrument is very old and has been discontinued for many years.We do have an adjustment procedure for this instrument in which we can Test/Evaluate and adjust the instrument according to manufacturing specifications. The cost for this is $150.00.** should we find this instrument defective and we are not able to successfully complete the work/repair, there will not be any charges to you.Hrm. $150 or $175, I can probably put that to better use with a new scope/meter. Looks like that Uni-Trend UT81b is about $216 on Amazon, The Owon HDS1021M is about $232 on Amazon. Anyone have any opinions on those ? We all know Dave's opinion on the larger "normal" Owon scope ...

author: Unknown
author_rank: Unknown
timestamp: October 09, 2013, 04:07:29 pm
content: Mike (mikeselectricstuff on Youtube) did a video review of two Owon handheld scopes. He considered the DMM feature pretty much unusable. I think someone on this forum (Aurora?) has done a review on the UT81. A Google search should be able to find both.I would take a stab at repairing the Extech. Did you ask them for schematics or service docs? I would start with the power supply and input circuit. It might be something like a fusible resistor, MOV or PTC. Note readings with open and shorted leads, and look at a typical input circuit (Dave did a tutorial, search for input protection on his Youtube channel). Do scope or current functions give sensible readings? This gives you info on whether the failure is in a circuit common for both.You might be unlucky and find a failed unobtanium ASIC, but it could also be something trivial like a dried out cap in the DC-DC converter.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 09, 2013, 06:01:28 pm
content: QuoteI have a roughly similar unit, a TPI 440, which combines a multimeter with a basic one-channel low-bandwidth scope. I've had it for roughly ten years.Its display is slow, and difficult to read with low contrast. It has become worse over the years. It almost requires the constant use of the backlight to make it readable, and the backlight cuts into the already shaky battery life. The firmware and UI are difficult to navigate. The oscilloscope seems to be AC-coupled only, which limits its usefulness with slow signals, as long square waves always exponentially decay toward 0. It's more of a "crude waveform viewer" than a "precision oscilloscope". Given that it costs more than a Rigol DS1052E these days, and the Rigol absolutely beats the pants off of it in every category except portability, I can't recommend it as a scope unless portability is your only concern, you never deal with signals above 1MHz, you don't deal with slow signals (that AC coupling issue), and you're content with a crude view of waveform shape. It's a "portable audio waveform viewer", not a proper oscilloscope.As a multimeter, it's ok, with a lot of great capabilities, but the display is difficult to read, battery life is lousy, it's bulky, and the menus are a source of frustration. I bought the TPI 440 at about the same time as I bought a Fluke 16, and the contrast is striking. The TPI does everything, but is frustrating to use. The Fluke 16 has very few functions, but they work quickly and well, with a very readable display. Over the years, when I'd have a task and need to pick a meter, I'd pick up that simple Fluke if the job was something that was within its capabilities.I have heard of car stereo installers using it to set gain on amplifiers, where they can feed a triangle wave into an amp, and use the waveform viewer to check when the amp starts clipping. I suppose if I did a lot of that kind of task in the field, and nothing else, I might like the portable audio waveform viewer. But these days, if I needed to do any serious scope work on a car, I'd probably drag an extension cord out and fire up my Rigol DS1052E -- it's only a little bit bigger and a LOT more pleasant to use and capable.I don't have a lot of experience with other similar products, so I can't say the unit is better or worse than other handheld oscilloscope/multimeter combos. But the weak display and frustrating UI make me hate using the thing, so I'd give it a thumbs down.

author: retiredcaps
author_rank: Super Contributor
timestamp: October 09, 2013, 10:01:39 pm
content: Quote from: halfwalker on October 09, 2013, 03:52:29 pmThe Extech meter needs to be on and set to DCV mode when measuring its input impedance. It should be around 10M ohm.QuoteSome of the battery juice may be on the pcb? I suggest giving the entire pcb a thorough IPA wash/bath (scrub gently with a clean toothbrush) and lettting it dry at least 1 to 2 days.You have nothing to lose trying the above given that Extech wants at least $150 USD.If you have no interest in repairing this or working further on it, send me a PM.