Should I get a Fluke? What other brands? - Brymen BM869s and UT71E Repair

[OiD]

Hi all!

Sorry, another "what dmm should I get"!

I've had my fair share of 20€ meters and 3 years ago I picked up a very nice UNI-T UT71E in China for 90€... and as habit goes I end up damaging them.

Mostly all of my meters have been damaged by high voltage spikes from inductors. Im looking for something that can tolerate high voltage spikes.

Flukes are nice, I use them at work along with Agilents and Amprobes wich are also nice... as is the price...

I'd like a Fluke (or other quality meter) that can tolerate HV spikes. I don't work with 3-phase systems but I go from millivolt to rectified single phase mains. Safety is important but I don't think my use in these cases justifies the expense of a high end DMM.

Features I'm looking for in order of preference are;
Spike tolerance
AC+DC / RMS / DC 0.5%
Microamps
10A range
Watt meter
Frequency/Duty
RS232/Infrared/USB Comunications

Fluke 179 / 116 / 789 are close to what I'm looking for. The price of the 789 is a lot more than I'd like to pay though!

So I'm thinking of getting two DMMs. One that is robust and good quality with the basics, plus another full featured cheaper meter and incorporate some external protection for the inputs.

Ideas are welcome as are DMM suggestions. While I have a complete workbench with nice equipment I have always "cheaped out" on DMMs. It's time to get a good one!

Gossen? Meterman? Hioki? Protek? Uni-T?

Short version; One over the top and quality DMM with robust inputs or one quality DMM and another cheaper one with all the features?

Thanks!

[EEVblog]

Very few meters on the market have a Watt meter

[retiredcaps]

Mostly all of my meters have been damaged by high voltage spikes from inductors.

How high is high?  500V? 1000V? 2500V?

[nanofrog]

Whatever you end up getting, the highest would be CAT IV @ 1kV (required to handle a transient of 12kV). Take a look here for the current CAT transient values (nice chart at the bottom of the page).
 
To get a quality meter but not have to pay Fluke or similar pricing, check out Brymen. For the feature set you want, I'd suggest the BM869S (no Watt meter, but that's not common). The reason being it has to measure both current and voltage simultaneously. And AFAIK, the Gossen Metrahit Energy is the only one that does; and it costs a mint.

Get a Kill-a-Watt or similar device if you want to see the power drawn from an outlet (energy usage monitor). Or measure current & voltage with a meter and do a little algebra.

[retiredcaps]

I've had my fair share of 20€ meters and 3 years ago I picked up a very nice UNI-T UT71E in China for 90€... and as habit goes I end up damaging them.

BTW, if you want to try and fix some of these damaged meters for future low voltage use or as a learning experience, start a new thread and I may be able to offer suggestions.  Only a handful of us are interested in repair while most will say junk/toss the meters.

[OiD]

Very few meters on the market have a Watt meter

Very true. It's a nice feature especially if the meter has datalogging/usb/serial interface with power factor, frequency, voltage and current at the same time.

Mostly all of my meters have been damaged by high voltage spikes from inductors.

How high is high?  500V? 1000V? 2500V?

Well, most of the ones i've damaged have been with boost circuits pushing the limits of the multimeter (near 1000V) and a slip of a component/potenciometer sending quite a few more electrons to the DMM. Others have been a one off of disconecting a large electromagnet or other coil with the DMM still attached. I'm guessing the 2KV-4KV range is where they fail.

Thanks for the chart, it's nice and clear!! Is the Brymen BM869S CAT rating internal or third party certified? Is there a way to tell?
The kill-a-watt aproach is interesting, I have a similar one but its a bit clumsy to operate. Since owning the UNI-T I've only had to use two meters to measure DC power, as the UNI-T only did AC 

I've had my fair share of 20€ meters and 3 years ago I picked up a very nice UNI-T UT71E in China for 90€... and as habit goes I end up damaging them.

BTW, if you want to try and fix some of these damaged meters for future low voltage use or as a learning experience, start a new thread and I may be able to offer suggestions.  Only a handful of us are interested in repair while most will say junk/toss the meters.

Are there cases where there is a replacable components? Or does it involve replacing the processor? Sounds interesting!

Thanks for the input! CAT IV 1000V looks like its the path to go  Will also be safer with high voltage capacitor banks!

[nanofrog]

Thanks for the chart, it's nice and clear!! Is the Brymen BM869S CAT rating internal or third party certified? Is there a way to tell?
The kill-a-watt aproach is interesting, I have a similar one but its a bit clumsy to operate.

I'm not sure if it's internal or 3rd party, but they have had meters with the UL logo printed on them. It may just be a matter of not enough room to fit a UL logo. Regardless, they've been taken apart and investigated to find that they do have protections sufficient to meet their stated CAT ratings (S versions were introduced to meet the latest standards). 

And another member joeqsmith created the Handheld meter electrical robustness testing thread where he's been testing them.

[Fungus]

Short version; One over the top and quality DMM with robust inputs or one quality DMM and another cheaper one with all the features?

One meter that has proved nearly impossible to kill in tests is the Fluke 101, You can get one for about $42, shipped.

The 101 doesn't measure current but you can have another meter for that (or use a shunt). You can never have too many meters. 

For a second meter with more features you can get one of Dave's Brymens or if you prefer yellow a Fluke 17B+ for a similar price.

What was the budget...?

[retiredcaps]

Are there cases where there is a replacable components? Or does it involve replacing the processor? Sounds interesting!

It all depends on damage and what input protection there is in the meter.  Two recent examples.  Brymen BM869 where the user was possibly measuring a microwave transformer and another where user used a Fluke 177 to measure a microwave transformer.  Both are/were fixed for less than $10 USD, but may not meet their original safety listings.

https://www.eevblog.com/forum/repair/brymen-bm869-meets-high-voltage-in-real-world/

https://www.eevblog.com/forum/testgear/fluke-177-schematic/

In other cases, the main IC is bad and while possibly fixable, it is probably not economically viable in a $20 meter.

[Lightages]

FYI, Brymen gets all of their meters tested by third party labs. They all have UL labs certified ratings.

[nanofrog]

FYI, Brymen gets all of their meters tested by third party labs. They all have UL labs certified ratings.

I couldn't sufficiently prove this (was hunting BM869 photos as well as its datasheet for the UL logo), so thanks for the clarification. 

You might make a suggestion that they do so on their datasheets, as stating meets xxx standards isn't clear as to whether or not it's internal certification or by a recognized 3rd party.

[Lightages]

I will provide a proof here to help.

[rsjsouza]

Fluke 179 / 116 / 789 are close to what I'm looking for. The price of the 789 is a lot more than I'd like to pay though!

I have a Fluke 179 that was submitted to some abuse (low energy 2kV spikes and some 20~30s 1050~1100V continuous input) and it is working very well. It is built like a war tank.

I also have a Brymen (an older BM857 model) and can attest its build quality is excellent.

Obviously you can always go the route of having a HV probe (as discussed here).

One meter that has proved nearly impossible to kill in tests is the Fluke 101, You can get one for about $42, shipped.

Obviously that you can't deny Fungus' nice recollection of the near indestructible Fluke 101. That is some hard to kill DMM.

[lowimpedance]

I've had my fair share of 20€ meters and 3 years ago I picked up a very nice UNI-T UT71E in China for 90€... and as habit goes I end up damaging them.

Mostly all of my meters have been damaged by high voltage spikes from inductors. Im looking for something that can tolerate high voltage spikes.

 Perhaps you should take a different approach, as has been suggested and get a suitable high voltage probe for those 'destructive measurement occasions' and also say the fluke 101 etc to cover the other type of measurements that wont involve feeding meters to it.
 
 As for repairing the others , well that is something for you to decide if its worth the effort. However if you just want to use it as a learning experience then sure go ahead.
I certainly have as the learning is cumulative. But with this learning also comes the ability to know when to say its junk and move on. Take the fluke 177 thread that unit is seriously compromised safety wise and its a 'luck of the draw' as to what else has been damaged and just how long it keeps going after any repair.
 Of course that 'knowing' gets a little blurry when its say a Fluke compared to the 20€ ones, (I am no different here either).
 Also parts availability and 'donor' units will vary depending on you location.
Rather than feeding meters to a measurement situation perhaps step back and question what is happening before deciding where to spend the money.

[R005T3r]

Very few meters on the market have a Watt meter

The R&S HMC8012 DMM have a power measurement capability. Here's a review:

[OiD]

Hi all!

Thanks for all the suggestions. After viewing most of joeqsmith's videos regarding his tests and that the meter is UL certified for 250€ shipped with all of the features I'm looking for plus some (except for the wattmeter part, but then that was just a nice extra of the UT71E) I finally went with the Brymen BM869s. I just wanted something nice with some actual protection regarding random spikes. Didn't matter if it was yellow, red, green or blue! 

The USB adapter is a bit pricy, but it includes their software i guess. Is the Brymen protocol standard or open?

Now to see if the UT71E is repairable  Resistance, diode, continuity, capacitance, uA, mA are damaged. Voltage shows different values if the polarity is swapped 
Anywhere to learn about DMM input protection circuits? or is it just resistors, MOVs, PTCs and clamps?

I'll also look into external protection circuits, attenuators and at least one DIY HV divider. Have a 150KV project in the no longer so distant future.

Again thanks!

[retiredcaps]

Now to see if the UT71E is repairable  Resistance, diode, continuity, capacitance, uA, mA are damaged. Voltage shows different values if the polarity is swapped 
Anywhere to learn about DMM input protection circuits? or is it just resistors, MOVs, PTCs and clamps?

Unless your UT71E is different from Dave's eevblog 712 episode,



it looks like the Uni-T input protection is lacking with just a single PTC.  Chances are your main IC is fried.

Questions.

Q1) Does meter show 0.00 when set to DCV with no probes attached?
Q2) Does meter show 0.00 when set to ACV with no probes attached?
Q3) Does meter show 0L when set to ohms with no probes attached?
Q4) If you measure an AA 1.5 cell, do you get 1.5V DC?
Q5) If you short the probes with meter set to ohms, do you get close to 0.0?

To learn see Dave's episode 373.

[joeqsmith]

Anywhere to learn about DMM input protection circuits? or is it just resistors, MOVs, PTCs and clamps?

Hey, you bought my favorite meter.  Hope you enjoy it as much as I have mine.   Other then damaging mine as part of the testing I have done with all of the meters, I have not had any problems with mine and it gets used a fair amount. 

How many Watts is the 150KV system you are working on?   Any other info?

I have made a few videos on the input protection.  After various members recommended adding MOVs to the UNI-Trend UT61E for some reason or another, I made two videos showing what it would take to make it a more robust meter.     
 


This one was after Dave posted on a Keysight meter using GDTs.  Basically it shows the switching times of MOVs compared with GDTs. 

[joeqsmith]

One meter that has proved nearly impossible to kill in tests is the Fluke 101, You can get one for about $42, shipped.

   This is Fungus's meter.  I never would have ran it had he not brought it to my attention..

The 101 has survived a 13KV 100us FWHH transient with a 2 ohm source.  Another member repeated this test using a commercial transient generator at 12KV 50us FWHH 2ohm source.   I have yet to take mine apart.   

The 107 that 5KY provided me survived at 14KV 100us FWHH with a 2 ohm source!  This is by far the hardest I have pushed a meter and have it survive.

The EEVBLOG rebranded Brymen survived at 10KV 50us FWHH with a 2 ohm source.  One day I will run this meter along with the Fluke 101 and 115 to failure like I did with 5KY's Fluke 107.   

While there are a few meters like these that are the kings of my testing,  my personal favorite is one of the least robust meters I have looked at, the UNI-Trend UT181A.  This $300 was damaged with the very first pulse from the grill starter.  Once repaired, I went through the whole front end and changed the design.  I then retested this same meter with the grill starter and then all the way to 15KV 50us FWHH with a 2 ohm source.   

From what I have seen, UNI-Trend could really improve their designs without too much effort.   

[OiD]

I saw Dave's video of the UT71E a few months after I bought it. But for 90€ total and no way of contacting the seller...  Meh.

I've attached some photos of my UNI-T. It was in volts range. No idea how the fuse and pad of the selector dial blew but... the did i guess.

Now to see if the UT71E is repairable  Resistance, diode, continuity, capacitance, uA, mA are damaged. Voltage shows different values if the polarity is swapped 
Anywhere to learn about DMM input protection circuits? or is it just resistors, MOVs, PTCs and clamps?

Q1) Does meter show 0.00 when set to DCV with no probes attached?
Q2) Does meter show 0.00 when set to ACV with no probes attached?
Q3) Does meter show 0L when set to ohms with no probes attached?
Q4) If you measure an AA 1.5 cell, do you get 1.5V DC?
Q5) If you short the probes with meter set to ohms, do you get close to 0.0?

A1. 0.0135V ish
A2. 0.0000V
A3. OL -> Meg range - > K range -> Loops back to OL
A4. Brand new Alkaline 1.6018V and if I reverse the polarity -1.5618V
A5. No reaction. Loops through the ranges.

Anywhere to learn about DMM input protection circuits? or is it just resistors, MOVs, PTCs and clamps?

Hey, you bought my favorite meter.  Hope you enjoy it as much as I have mine.   Other then damaging mine as part of the testing I have done with all of the meters, I have not had any problems with mine and it gets used a fair amount. 

How many Watts is the 150KV system you are working on?   Any other info?

I't should arrive on monday, I hope not to be disapointed 

The 150KV is DC. I still need to build the capacitors for some smoothing. I Don't know how much enegry they will store as I don't know what vallue they will be yet. I'll try to keep it as low as possible. The end device is a 75W X-ray tube. No hurries in building it. Gotta do it properly!

One meter that has proved nearly impossible to kill in tests is the Fluke 101, You can get one for about $42, shipped.

While there are a few meters like these that are the kings of my testing,  my personal favorite is one of the least robust meters I have looked at, the UNI-Trend UT181A.  This $300 was damaged with the very first pulse from the grill starter.  Once repaired, I went through the whole front end and changed the design.  I then retested this same meter with the grill starter and then all the way to 15KV 50us FWHH with a 2 ohm source.   

From what I have seen, UNI-Trend could really improve their designs without too much effort.   

Guess I'll have a look at how that test went. The meter looks very nice, but Color/OLED/TFT displays on a DMM screams caution to me 

[retiredcaps]

Measure PTC1.  I'm guessing it should be about 500 to 1500 ohms.  You can measure in-circuit.  Report your findings.

[OiD]

Measure PTC1.  I'm guessing it should be about 500 to 1500 ohms.  You can measure in-circuit.  Report your findings.

PTC1 is 1.2K

Adding some more photos

[OiD]

And some more photos of the physical damage!

[joeqsmith]

Did this meter come new with glass fuses?   I am used to seeing the Asiafuse filled ceramics in them.   

I did a video where I showed some clips of the UT90 which has received some pretty bad damage since I purchased it.   I showed how I had repaired missing sections of the selector switch using some epoxy and foil then soldering 30AWG wire to it. 

I assume the damage is all tied to the 10A circuit and if that's the case, maybe it didn't damage the controller.  Still, may take more effort than it's worth.  Anymore I repair the UT90 out of principle.   

[joeqsmith]

Here are a few pictures showing some of the repairs (which is an overstatement  ) to the UT90A.   It may give you some idea how to repair the damaged circuit board.