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    Written by: Kiriakos A. Triantafillou, Industrial maintenance electrician, Hellas. (2012 -> 2023 -> 2025)
Digital Multimeter, Clamp on meter, Oscilloscope, Electronic component testing tools.

BRYMEN BM878 Insulation Tester Combination Multimeter review

By the eye of the Industrial electrician.  

Written By Kiriakos Triantafillou – Greece    25 April © 2019

1) Intro  

In the world of Electricians, we are aware that electrical theory when combined with thousands hours at a work site this is the recipe which generates our priceless experiences.

What is not written at any books and neither among Google search results, this is that if you have limited perception of entire picture of what called as electrical circuit, then you will never become a successful troubleshooter.
Concept of body-building this is identical as example and for us electricians, we need to focus by our self’s over several electrical circuit (unseen by naked eye) parameters and by the use of special tools, we to further develop our own understanding and skills (regarding troubleshooting).   

Even in a perfect designed electrical installation, problems they do occur when physical condition of materials in use this degrades.
Known enemies are high temperature or high humidity, or contamination which this lowers electrical insulation, and last hard to see enemy this is physical damage especially at underground cables.  

This time thanks to BRYMEN (electrical test and measurement equipments’ manufacturer from Taiwan), I am going to deploy my thoughts and product review of BM878 which this belongs in a relatively new concept of tools, named as Insulation Tester Combination Multimeter.

Few years ago such a concept of a tool named as Insulation Tester Combination Multimeter was unknown.

BRYMEN BM878 mainly this is a pack of three instruments in to one body.
a) Features rich multimeter for installer electrician and industry.
b) Insulation tester with high degree of measuring accuracy and respectable specifications’.
c)  Earth ground resistance tester (milliohm meter function), ground wire inspection of electrical appliances and of installed machinery at industrial work sites.

Personally back at 1998 in which I was an graduated electrician (in the age of 19 years old), basic information of insulation tester equipments was limited down to one model, and this was a Megger analog Meg-Ohm-Meter with metallic rotating lever at the side.
Neither our teachers were truly informed about details as for example measuring results analysis.
My classroom received brief information about the theoretical concept of using such instrument (Mega-ohm-meter), and this was all about it.

Today I am a 49 years old freelancer industrial maintenance electrician and electronics repairs specialist.
Specific product review this helped me to rediscover the world of resistance elements, starting from hyper conductive materials (milliohm's) up to Giga-Ohms with just a single meter at hand.
2) BM878 quick description of strong points

BM878 this is described as multi-tool and there is only one way to properly evaluate it and understand what this is, and you can do this is by breaking down the long list of it features.
Before I do start this features list breaking down, I must mention the only thing that BM878 was not designed to measure and this is direct current 10A range, instead those banana jacks they are occupied for the Low resistance circuit.

In the general specifications’ list we will discover rich specifications’ them be proofs that BM878 this is modern and very fast, this qualifying standing among three best handheld solutions in the market (worldwide) at 2019

Display: 3-5/6 digits 6,000 counts
Polarity: Automatic
Update Rate: 5 per second nominal
61 Segments Bar graph: update 40 per second max
Operating Temperature: -10°C to 40°C
IP Rating: IP40
Sensing: AC, True RMS
Overload Protections:
Insulation Resistance & mA: 0.4A/1KV, IR 30kA or better
Earth Continuity Test: 0.25A/1KV, IR 30kA or better
Volt range: 1100 Vrms
mV, Ω & Other functions: 1000 Vrms
Transient Protection: 8 kV (1.2/50µs surge)

Here are multimeter sector features of BM878:
1) Milliamperes measurement for process control
2) Temperature measurement
3) VFD ACV filter
4) Capacitance measurement
5) Diode measurement
6) AC/DC Millivolts + Hertz
7) Continuity
8) AC Volts & DC Volts

Now let’s focus at BM878 (highest importance) three SPECIAL functions:
1) Milliohm meter measuring from 0.015 ohm up to 2 Ohms with five digits resolution, by injection of constant current at 200mA as highest option and of 75mA too.
2) Ohmmeter this measuring from 100 Milliohm up to 50 Megohm.
3) Insulation resistance measurements in a range of single Megohm up to 25 Giga-Ohm.

The quick conclusion here this is that with one BM878 at hand, I can measure anything that is labelled as resistance from 0.015 ohm (15 Milliohm) up to 25 Giga-Ohm.
Imagine now that a rocker switch contacts resistance when new, this is listed as 35 Milliohm or less (0.035 ohm).
In my eyes the fact that a single handheld meter this now comes loaded with three special resistance's measuring circuits, this is something remarkable.
There is no regular multimeter able to compete with one BM878, because this is a special tool able to compete only with similar ones at the category of insulation resistance testers and only with the best ones made in USA or Germany.
3) What is in the box?

BRYMEN ships BM878 with rich package of accessories.
a) Pair of test leads at 1KV CAT II for their 600V measuring multimeter with metal threads at tip ends, it accepts banana barrel attachment or plain barrel attachment.  Additional plastic covers for the tips these elevate safety specifications’ to 1KV CAT IV as soon they got installed.
b) Pair of insulated alligator clips (Them made under newest safety specifications’).
c) K-type probe up to 250 Celsius.
d) Single large in dimensions insulated probe (Red) for Insulation and low resistance measurements’.  Insulation this is double than regular probes and also includes a test switch with identical functionality with the test switch over the meter it self.

The number and diversity of accessories this is significant, I would expect that BRYMEN it would have include some sort of hard case for it, this including storage compartment for its one type of accessory.

Now regarding specific BRYMEN Remote control probe, you should be aware that you need be careful, to insert it plug all the way in, this translates that you have to push much harder than when you connect regular banana test leads.
Push or Pull of specific probe plug this is not a major problem, because this has oversized enough top end, which is manageable even by people having large fingers too.
4) BRYMEN BM878 Insulation Tester

BM878 insulation tester product specifications:

BM878 Insulation Tester (voltage output / resistance range) specifications’:
50V:  3M to 55M
100V: 3M to 110M
250V: 3M to 275M
500V: 3M to 550M
1000V: 3M to 25.0 G Ohm
Accuracy specification:
From 50V to 500V this is:  1.5% + 5 digits
At 1000V at resistance range up to 300M = 1.5% + 5 digits
At 1000V at resistance range up to 3000M (3G-Ohm) = 2.0% + 5 digits
At 1000V at resistance range up to 25G-Ohm = 10% + 5 digits

Because of BM878 insulation tester I was forced to make a special resistors box this including GST4020 (4000 Volts operating voltage) resistance elements at below values and tolerances:
1M Ohm 0.25%
10M Ohm 0.25%
39M Ohm 0.25%
50M Ohm 0.25%
100M Ohm 0.25%
200M Ohm 0.25%
2.45 G Ohm 0.25%
16 G Ohm 5%

Thanks to Vishay Foil Resistors brand I did manage to acquire necessary samples.

BM878 at Insulation Tester mode, at 50V test voltage this can measure low resistance down to and not less than 10K, and at 100K ohm and above, measuring precision this gets restored according to manufacturer specifications’.

Testing of BM878 in the range of 10K to 900K this performed due our latest seven decades resistor box this made by hermetically sealed Vishay Foil Resistors, all Calibration standard class, at tolerances of 0.005%.
One of reasons making this test was for me to investigate usable display digits resolution, this is a 6000 counts meter, at 900K Ohm test BM878 this measured 0.900 at it lowest 3000 K-Ohm ( 3 G-Ohm) resistance range.

When BM878 Insulation Tester was tested against High-voltage & High-resistance elements of high precision, this demonstrated very good performance regarding measurement accuracy and a stable measurement (displayed digits), with remarkable repeatability.

Today I can say with 100% confidence that BM878 at Insulation Tester mode and regarding it measuring performance at measuring error tolerances this is superb up to 17 G Ohm that is the limit of my own verification box for Insulator Testers.
5) BM878 ground wire Tester

In the question of why industry selected use of 90mA and 200mA as test current in modern ground wire testers, this is explained at special IEC handbooks.   
The quick explanation this is that for ground wire tests it is not required any more injection of high number of Ampere.

In this function, BM878 becomes a Milliohm meter measuring from 0.015 ohm up to 2 Ohms.
Now such a Milliohm meter combined with 200mA test current, this is a sufficient test and verification that ground wire it self and connection points, all are in good condition and it will work as protection against electrocution.

In our days in which RCD relay this expected to disconnect live circuit in case of an accident, the job of ground wire tester, this is verifying that a wire is capable to transfer a minimum current which this is also enough for RCD relay activation.

Other uses of such Milliohm meter combined with 90 & 200mA test current they can be rocker switch contacts resistance measurement.
Telephone cables inspection (pairs testing) and even in LAN installations, patch panel quality tests or troubleshooting and finding a single damaged wire.
6) BRYMEN BM878 Combination Multimeter & conclusion

Lately produced digital insulation testers they do come with several options regarding test output voltage, usually from 50V with several steps up to 500V or up to 1000V or even higher.
Ancient Megger (Mega-ohm-meter) this is now device for museums

Low voltage applications this is telephone lines and or PC networks cabling.
Regular voltage applications these are anything we know operating from 120V up to 380V AC and as High voltage applications ( 1000 ~ 2500V )I will describe anything relative to energy transfer at solar parks and other renewable energy production sites.

Industrial applications at low volts in which cables insulation it is of high importance such can be:
Telephones and intercom devices, data lines for PLC system programming, alarm systems sensors (fire alarm - burglars alarm), emergency stop switches and many more.  

It is not unusual event in factory facilities to watch a forklift vehicle to monetarily crash it shelf over building pillars, its pillar it can also carrying several surface mounted cables them with several internal wires.
Therefore mechanical damage could be No1 suspect for insulation failure, and this is even harder to detect at underground installed cables.

Application examples for 120V / 250/500V test voltage.
Known principal this is insulation testing at double test voltage than the expected as operational voltage, therefore feel free to assume that an American electrician would use 250V as test voltage and the European would use 500V instead for wires serving Mains voltages.
From the other hand they are aspects’ identifying its one insulation testing process as unique and therefore we must be aware of complete picture of its one specific electrical installation.

For example in a factory which I did worked in the past, they was having wall plugs supplying 120V AC about serving made in USA machinery, among with 220V AC (regular for us) wall plugs ,  among with wall plugs them supplying three phase 380V AC.
Therefore in a single room I came face to face with three different wall plugs, three different voltages and also three electrical standards.

Application examples for 1000 Volt and beyond regarding test voltages this is a sector of rarer known electrical applications, or of fresh introduced ones.
For example at mining and rock excavation, at underground tunnels they use electric fans for atmospheric air distribution which them operating at 1000V.
Fresh introduced and rather in experimental stage application this is high-voltage DC at 2500V which is used at solar energy production facilities (solar parks).
And I will assume again that such technology this is again developed for the purpose of balancing or minimizing energy loss due several hundreds of meters length of the installed cables.

In conclusion, benefits obtained by the use of modern designed insulation tester, these are not limited as assistance in favor of public safety by classifying circuits as Passed according to specifications.
I think now of insulation testers as important tool and for freelancer electricians about them using such a meter especially for troubleshooting purposes’.

Specific BRYMEN BM878 this is a pack of three instruments in to one body, this is quite invaluable offering of features which you should spend other than money and a bit of time, so you to extend your own understanding of how to use its function.

BRYMEN in Taiwan this is now famous of making quality multimeter, this is why I did basic tests at its one multimeter functions’ with out writing any analysis.
Instead I did focus on insulation resistance and ground wire tester capabilities, because greater awareness regarding these features’ it can help you own productivity and wallet in the near future.  

As professional electrician and Blogger all that I am going to say is that up to date (within seven years of time), all my experiences with BRYMEN tools them are positive regarding build quality.

I wish to thanks BRYMEN for sending also this product for a public review, ITTSB Blog monitoring all vendors worldwide for several years up to date, and BRYMEN this is one of the most energetic! at listening their customers voice and at accepting feedback for their products.
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