OWON Multimeters: Opinions, Likes/Dislikes, Problems, Hacks/Mods

[MrCreosote]

Did a lot of research looking for an onboard data logging DMM w/thermocouple K and graphing capability (through BlueTooth or PC, in this case.)

The the winners were the B35T+  and B41T+ at $55 and $95 shipped.

There is virtually no reviews of these models, hence the thread. 

I suspect there will be poor input protection but for the money, these meters are Crazy Eddie cheap.

I can't wait until they put a graphical display in this class for trend plotting too.  That would be the Whole Nine Yards.

COMMENT:  The tech is there to make a single device that does everything.  It's going to be fun to watch this revolution - the final feature will be do you want a hand held or desktop UberScope.

[claytonedgeuk]

I've been keeping an eye out for the b35t as well..but I'm not quite brave enough to buy one.  Though for that sort of money you're in mooshimeter territory...and the benefit there of reading V and I together.  Not keen on those?

The analog discovery does a pretty good job of doing an all in one...admittedly not over bt though.

[bitseeker]

Couldn't help but notice that those two models spell BEST BAIT.

I haven't heard anything about them, either.

[xrunner]

I have  B35 coming in a few days, so I'll be playing with that very soon.

[bitseeker]

What timing. I shall watch for your review.

[xrunner]

There is an iOS app for it and it's on my phone just now. Now just waiting for USPS ... 

[kwass]

I suspect there will be poor input protection but for the money, these meters are Crazy Eddie cheap.

"Crazy Eddie"!  How many people on this forum could possibly get this reference, I gave him some of my hard earned money for some mightily inexpensive consumer electronics in the 1980's.    [For the uninitiated, Crazy Eddie was a chain appliance/electronic stores in the NY City area that sold at a very good discount and was promoted by "his prices are INSANE" ads on television.  Every time you'd go into one of these stores you would get the distinct impression that this operation could not be on the up-and-up.  It was not, but somehow lasted for a good many years:  https://en.wikipedia.org/wiki/Crazy_Eddie]

Back on topic....  The BT35+ is a cheaply made meter, that really wouldn't be worth a second look if it didn't have bluetooth.  The display is okay as is the backlight.  Continuity test is latching and loud, but really, really slow to respond.  Here are some pics:

[xrunner]

It has arrived.

More coming ... 

[xrunner]

Since we already have a few pics above, I'll just go over a few things for now. I measured a 10V reference I have, which my HP 3468B read as 10.004V. The B35 read it as 10.03V

The accuracy spec for DC voltage is +/- (0.5% + 2 counts). So for this reading it would be +/- .05V + 2 counts, so on that scale it would then be +/- .07 V so it's within the spec.

On the faceplate it also states that -

20A Max

Each 15 min Max 10 sec.

Meaning, I think, that it can measure 20A Max for 10 sec but only once every 15 min.

Capacitance and resistance measurements looked good.

Is it cheaply made? Well, I've seen worse I guess but it's OK for the price so far. It came with a nice carrying bag and leads/attachments such as a K thermocouple and an attachment to assist in measuring caps/resistors and transistors.

I only played with the Bluetooth for a few minutes today but it was very easy to connect to my iPhone. I just watched the DC measurements draw a straight line, but will test more tomorrow. It does have a voice annunciation that states the reading each time if you wish it to, but my cat hated to listen to it. I need to get into the interface more tomorrow. 

[kwass]

Since we already have a few pics above....

It might be interesting to see a pic of the board inside to compare it to the B35T+ posted above.  It might be possible to add True RMS (that's the 'T') and in-device memory (that's the "+") by just adding a jumper or two.

[xrunner]

It might be interesting to see a pic of the board inside to compare it to the B35T+ posted above.  It might be possible to add True RMS (that's the 'T') and in-device memory (that's the "+") by just adding a jumper or two.

Hmmm, yea might be worth a look. Have you tried the Bluetooth functionality?

[bitseeker]

On the faceplate it also states that -

20A Max

Each 15 min Max 10 sec.

Meaning, I think, that it can measure 20A Max for 10 sec but only once every 15 min.

Correct. It needs time for the shunt to cool down and recover. Even at half that current level, most DMMs I've used will drift as you're taking the measurement due to the shunt heating up.

[xrunner]

It might be interesting to see a pic of the board inside to compare it to the B35T+ posted above.  It might be possible to add True RMS (that's the 'T') and in-device memory (that's the "+") by just adding a jumper or two.

Here's mine. It says it's B35T v1.5 2016.10.2

Changes have been made ...

I want to know how to cal it, specifically what each pot controls on the board.

[kwass]

I want to know how to cal it, specifically what each pot controls on the board.

See the reference schematic for clues on the DMM4 data sheet here: http://www.ic-fortune.com/upload/Download/FS9922-DMM4-DS-13_EN.pdf

[xrunner]

See the reference schematic for clues on the DMM4 data sheet here: http://www.ic-fortune.com/upload/Download/FS9922-DMM4-DS-13_EN.pdf

OK, I'm checking it out.

By the way, looking at example DMM systems made with this DMM4 motherchip, it looks like the true RMS capability is provided by another chip such as an AD736 or the like. If you look at yours, you will see a "U10", but I can't tell what the writing is. On my B35, there is no U10 in place. I think U10 is the TRMS chip. Can you tell what chip they used for U10 on yours?

Played with the BT graphing a bit more. I set up a 0.1 sec square wave, and also diddled with a DC voltage randomly from about 15.5V to 16.5V. The fastest sample rate for the app is 1 sec, so you have to keep that in mind regarding the system response you want to monitor.

The app graph will only let you zoom in both axes at the same time. It will not allow just the Y axis to zoom in, and leave the X axis alone, at least I haven't found a way to do it. 

[MrCreosote]

I just got my B35T+ and have been focusing on the data logging aspects. 

THERMOCOUPLES:  One nice bonus is an input adapter that will accept mini thermocouple plugs and also serves as the transistor lead adapter.  Also, the TC included appears to have a white woven insulation with a blue stripe.  It is possible this is the high temp 1000*C mineral fiber insulation, however I don't know how to confirm that.  The TC probe has individual banana plugs instead of a mini connector. 

Big Disappointment was that it appears you have to use your BlueTooth device to initiate on-board data logging.

What is interesting is that if you open 4 stored files, you get 4 plots in 4 colors with tabs you can click to see the associated data.  This is very cool.  When these open, it appears that the x-axis is autoscaled for the number of data points.  I don't know what would happen if you had 1000 of them.

The BT app is not too bad all things considering.  For $58 shipped, yes, this is definitely "Crazy Eddie" (may "he" RIP) territory (loved the history lesson - I love those days of yore.  Loved the not on the "up and up" comment - like half the stuff fell off a truck  I had an aunt and uncle that lived in Roselle Park NJ, 10 min from Newark, and I remember his awesome, loud, and obnoxious radio ads!)

[kwass]

Big Disappointment was that it appears you have to use your BlueTooth device to initiate on-board data logging.

I thought that was pretty dumb too, I guess that the idea is that you can start the logging using your smartphone,  leave it running while you take your smartphone out of BT range, then return and grab the data from the meter.  I only tried this once and it failed.  Have you had any luck with on-device loging?

Loved the not on the "up and up" comment - like half the stuff fell off a truck

I'm sure it did.  He was selling for so much less than anyone else, it just had to be "hot", Japanese electronics.  As Dave days "all the best stuff is made in Japan" and back then everything was.

[kwass]

By the way, looking at example DMM systems made with this DMM4 motherchip, it looks like the true RMS capability is provided by another chip such as an AD736 or the like. If you look at yours, you will see a "U10", but I can't tell what the writing is. On my B35, there is no U10 in place. I think U10 is the TRMS chip. Can you tell what chip they used for U10 on yours?

It is a TRMS chip and surprisingly it's an AD8436, the JCPZ temperature version (0 to 70 deg C).  Quite an expensive chip for a low-end meter.

[Savoyarde]

Big Disappointment was that it appears you have to use your BlueTooth device to initiate on-board data logging.

The obvious reason, that you have to start the logging from your BT Device is, that the OWON DMM has no own real time clock. Logging without a timestamp is worth nothing if you want compare the data with other events.
I think the BT Device will send the starting time and the interval to the DMM and calculates the other timestamps when it receives the logging data from the DMM.

I testet the logging function with my B35T+. It is only useful up to 1000 logging records (max.10.000), because the Android App is to slow to handle the Data.

[xrunner]

After studying the DMM4 application datasheet (the DMM uses a Fortune FS9922-DMM4 IC) I found out how to cal the DCV functions, at least for the OWON board. As you can see it's quite a bit better than it was out of the box (before, it was reading 10.03 V for a 10 V reference. I'll put together some instructions and pics shortly. 

[bitseeker]

Nicely done, xrunner.

[xrunner]

Calibration of DCV for the OWON B35

To calibrate DCV on the OWON B35, you are going to adjust the "REFI" input to pin 4 on the DMM4 IC. As you can see in the attached datasheet, they say it's typically 0.63V. Mine measured 0.6326V before adjustment.

Measure the voltage between the two points I have labelled A and B. Hold your tongue like Dave and tweak away on VR6 unitl your readout is as close to your selected reference as possible. After adjusting, my REFI voltage was 0.6347.

Hope this helps any B35 owners out there. Next up is the ACV, I'm not satisfied with that cal either, be back soon ...

Note: Do so at your own risk, no warranties expressed or implied, I can not be held responsible for any bad results

[xrunner]

If you want to cal ACV it's adjusted by VR1. I tweaked mine and now the DCV and ACV are much better. Not sure why OWON couldn't have done a better job. 

[xrunner]

Ran across this - when measuring 5V I switched to the mV position, expecting to see an "OVLD" indication but instead it shows an odd reading of 59.59 mV. Found out by trial and error that anything under 2V, when switching to mV, will show Overload, but above that will show odd mV readings.

An Oopsie in the design? 

[kwass]

Ran across this - when measuring 5V I switched to the mV position, expecting to see an "OVLD" indication but instead it shows an odd reading of 59.59 mV. Found out by trial and error that anything under 2V, when switching to mV, will show Overload, but above that will show odd mV readings.

An Oopsie in the design? 

Maybe, or maybe it's just a way of saying that you're way beyond overflow 

A few other things to note about this meter:

- The back light times out in about 50 seconds, not 10 seconds -- at least in my model.

- There's no auto-power off indicator but the functionality is there. The meter will shut down in about 15 minutes with no user input, it will beep a warning about 1 minute before it shuts down.  Auto power off can be defeated by pressing and holding down the SELECT button when you turn on the meter.  It's also defeated in Bluetooth mode.

- The shunt resistors are lower in value than most similar DMM's:  .05ohms for the 20 Amp range, 0.5ohms for the mA ranges and 50 ohms for the uA range.  Measuring 100mA only has a voltage burden of only 50mV, pretty decent!

- There's some other functionality built in if you feel like hacking the main function switch.  There's RPM measurement and the ability use use a clamp-on current probe, for example.