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    Written by: Kiriakos A. Triantafillou, Industrial maintenance electrician, Hellas. (2012 -> 2024 -> 2025)
Digital Multimeter, Clamp on meter, Oscilloscope, Electronic component testing tools.
DIY resistance verification box for Insulation Testers with up to 4000 Test Voltage
Written by Kiriakos Triantafillou   February 2017 ©
1) Intro  

They are moments in which industries and producers of specialised tools for electrical measurements’ as for example Insulation Testers,  they do not predict to also release a relevant verification tool (in the form of accessory) so end user to be able to verify correct operation of Insulation tester by him self.

Additionally they are moments in which Insulation Tester product design this gets updated regarding specifications’, and test voltage value now this increases up to 4000V.
Also there is ITTSB Blog and Mr. Kiriakos Triantafillou whom working with passion at delivering content relative to electrical test and measurement equipments in the form of product reviews, and among test procedures there is verification of products specifications.

New born challenge for ITTSB Blog and me in person this is about designing and making a DIY verification box for Insulation Testers.
2) The challenge

For several years ITTSB Blog this is a source of content relative to product reviews of handheld multimeter.
Testing of highest Ohms measuring range this always was a challenge mostly because high resistance elements (large resistors) they are unpopular merchandize especially in small stores them serving Greek market of electronic components.

My own workaround at 2013 this was about me to buy eleven large resistors of ¼ Watt.
Then I use a project box among with a single rotating switch of nine positions this serving as selector.
By combining two or more resistors I managed to have a working resistors box with eight steps regarding Mega Ohm values, lowest this is 1M and highest this is 29.5M.
Back then, selection of any specific product specifications’ as for example their actual resistance value or about their working voltage among with measuring tolerance (%) this was a luxury which I did not have.
Even so I was very happy about what I did accomplished, mostly because I did succeed at making a simple verification box this having sum of resistance value that no true application will ever use in electronics, but still usable for my purpose which was testing (benchmark) of multimeter, and testing results was for my eyes only.

Unfortunately and as far I am aware of, most popular application for a multimeter this measuring high resistance this was HV transformers’ serving in televisions with tube technology, in recent years this application has vanish from most parts of our planet.

Insulation testers they are products especially designed to serve at measuring electrical insulation, and this is application with no expiration date.
Collapsed insulation at any electrical system this translates to death, or injure of people (if they are lucky), or in to tremendous damages in equipments and materials down to their total destruction point.
And first conclusion this is that all Insulation testers they are meters of tremendous value speaking of importance.
Measurements’ made by Insulation testers they do translate in to verification that everything is good, or as warning message about a critical upcoming event.

In recent years, over all product performance and build quality of Insulation testers, this is defined by strict electrical standards.
Compliance to such electrical standards this is mainly responsibility of any brand this making Insulation testers.
Unfortunately not everyone engaged in manufacturing of Insulation testers he can be trusted, low-cost products with out branding they do circulate from Asia to other destinations worldwide every day, most of them by not having any truly confirmed compliance, or a true mailing address of any product manufacturer.

First arrived at ITTSB Blog Insulation tester for a product review, this is BRYMEN BM878 multimeter & insulation resistance meter.
For several months I was looking to discover sources of high resistance elements made for such a special application.
Due Capital Control policy in the Banks of Greece (and for a very long time), I was unable to buy any goods from a foreign country, therefore I faced two serious problems both working against release date of this scheduled review.
3) Getting help from a specialist  
My decision to contact Vishay Foil Resistor brand this saved my day and this is a fact.
Thanks to Mr. David Gazit, Marketing | Vishay Foil Resistors | VPG, I become aware that POWERTRON – VPG brand, this having products them be close to my requirements’.

Thanks to Mr. Frank Weise, Senior Field Design Engineer | VPG Foil Resistors | Central & East Europe, I did receive the information that best product for such an application this is GST Series of Thick Film resistors.
Vishay Foil Resistor brand, kindly accepted to offer and product samples of GST series too so ITTSB Blog to use and evaluate.

After me studying (researching) GST series technical documentation, I did become aware that GST4020 this was the right product for me to use.
Also I did another greater discovery, and this is the magnitude of progress made over the years in the sector of resistors manufacturing process.

There is no easy explanations’ of how it is possible some one to manufacture such High Value resistance elements by them having that Low in percentage Resistance Tolerances.

Insulation testers able to measure up to 25G Ohm they have in their highest measuring range Tolerances as +/_ 7 to 10%.

GST4020 this can be ordered at >10G - 100G this having Resistance Tolerances of 5% to 30%, and lower in resistance elements they can be made at tolerances of 0.25% which this making them look as calibration standards to me.
Another unique characteristic this is working temperature of GST series and this is -55°C to +125°C.

Max.  Working voltage specification this it did confused me in the beginning, especially description of trimmed or untrimmed elements.
Mr. Frank Weise he kindly offered to me an explanation of tremendous simplicity and this helped me to gain further hints about How-To in the regard of technology used in production of such High Value Thick Film Resistance Elements.
4) My own choice of resistance elements

My decision from the beginning (planning stage of this project), this was me to create one verification box for Insulator Testers this able to test with precision its one measuring range.
I did review product specifications of several handheld Insulator Testers (from many brands), and then I did my choice of:

1M Ohm 0.25%
10M Ohm 0.25%
39M Ohm 0.25%
50M Ohm 0.25%
100M Ohm 0.25%
200M Ohm 0.25%
2.6 G Ohm 0.25%
16 G Ohm 5%

According to my plan all those resistance elements will be connected in series, and my resistor box will have several more measuring values due combination, and they are 11M, 50M, 100M, 200M, 400M, 3 G Ohm and final sum of 19 G Ohm.

According to handheld Insulation testers specifications’, these are their measuring ranges at specific test voltages:
50V:  3M to 55M
100V: 3M to 110M
250V: 3M to 275M
500V: 3M to 550M
1000V: 3M to 25.0 G Ohm
5) One high resistance system this is a huge challenge

When you are getting in the shoes of a product designer you also inherit all responsibilities of this position.
While it sounds easy to use a soldering iron and connect few resistors in series, when you are up to making a working high resistance system such degree of simplicity this does not apply.   

First of all you must take under consideration dielectric properties of its and every one material that you are planning to use in your project.
As such are Insulating resistance properties, high voltage limits and temperature.
Other significant considerations’ are relative to type of materials and their thickness and of necessary creepage distance.

My DIY project this ended in a tremendous success, because everything was planned by me taking in to account all necessary precautions to maintain a "clean" high-resistance system, such precautions are:
a) PTFE Teflon surface cleanliness
b) Creepage distance calculations
c) Resistor’s conductive contamination (after soldering).
6) Product design specifics’

Personally I am taking pride by combining good practices and by making something working and unique in design.

Cutting corners speaking of materials cost, this is possible only when performance this is not sacrificed in any way.

Product dimensions of GST4020 resistance elements are small, somehow I gained the impression that while they are perfect as product selection, they seemed as fragile to me and that I need to take extra precautions’ so their leads to not be stressed in any way.

By me selecting highest quality PTFE Teflon as base material, this helped me to drastically minimize cost of other required parts.
For example by me taking advantage of PTFE Teflon dielectric properties and of required Creepage distance, this choice helped me to use low voltage female banana sockets, and actually just their metal body.
Top colored cover of its banana socket this serving mostly aesthetics’ and also as visual indicator of Low to High resistance values.

Decision over what type of project box to use, this puzzled me for a long time.    
Best solution found to be a padded aluminium carrying case this to be used as project box and storage box (2 in 1 solution).

For labels and logos I did use again my HP 970CXi printer among with highest quality Gloss photo paper

I did all graphics design by my self, by using legally owned CorelDRAW X3.
Printed labels they are prone to damage as equipment labels and since 2010 I am using one workaround and this is about adding a piece of clear plastic of significant thickness at the top of its one printed label.
Last step this is one set of tiny screws, this keeps clear plastic and label in place.
7) Measurements and confirmations – QC Test

Insulation testers they can display measurement in four digits display resolution, and at their highest measuring range tolerance (at 25.0 G Ohm) this is +/- 10%.
My choice of GST4020 resistance elements at 0.25% tolerance this detail by it self makes my verification box this to gain the description of true measuring standard (electrical metrology).
From 1M up to 2.6 G Ohm all resistance elements are 0.25% with exception the larger one at 16 G Ohm this is +/- 5%.

Any such electrical measuring standard this it should be measured by an also highly qualifying meter, and as such this is RM3542A a high precision resistance meter made by HIOKI E. E. Corporation in Japan.
This is a meter with seven digits display resolution and it is also equipped with special comparator function this measuring at highest precision even single resistor tolerance in percentage.
Measurements results was 100% according to all resistance values named specifications’ regarding tolerance.

HIOKI RM3542A high precision resistance meter, this is able measuring up to 120 M Ohm.
I did a second verification by using this time HIOKI DT4282 handheld multimeter because this one can measure up to 600 M Ohm, and currently there is no second multimeter at ITTSB Blog up to date, with such extended measuring range.
At 400 M Ohm, HIOKI DT4282 this was able to deliver five digits display resolution.

Third and last verification test this was made by the use of real fire power this time, and this is BRYMEN BM878 multimeter & insulation resistance meter.
Naturally my description above this is result of my own enthusiasm, and this is equal to any product designer enthusiasm, when his prototype this passes successfully all tests.
For me that I am not a professional product designer, the fun factor and enthusiasm it is double or triples (By estimation).
8) Testimonial

Within 2017 they are branded sources worldwide and makers of measuring standards, and they do offer such special solutions.
My very own market research helped me at making several realisations’.

a) Such manufacturers’ they are not that many, and such products they look hidden as they are mostly presented inside of product catalogues.
b) Most to all of such manufacturers’ nowadays they do all use Thick Film resistors in their products.
c) Vishay Foil Resistors brand this is most popular choice about such products solutions (of high resistance elements) and a major provider in this products market segment.
d) Major customers of such products those are calibration labs, and this translates that high prices of calibration standards it’s not a major problem for them, those are tools of their job, they making money from them.
e) Currently only one or two brands made the thought so far, about them to deliver an simple version as verification box with three of four values of high resistance elements.
f) Insulation resistance meters nowadays they sold much cheaply than several decades ago that Megger brand in UK introduced such tools in the market.
g) While pricing of insulation resistance testers this is now much affordable, their electronics are and will be fragile and therefore verification of good operation this is a new obligation for any one using them, or else you cannot trust such testers in long term.
h) Unbranded insulation resistance testers this is not a tool that you can use and expect any reliability.

Personally I am tremendously happy with my new DIY solution of high resistance verification box for insulation testers with up to 4000V Test Voltage.
My plan was to create something with undisputable electrically correctness and this translates to spotless selections of build materials, product design, high quality resistance elements, and finally a true flawless made verification box.
Research time of my project this was tremendously long, as I was forced to study and discover all theory about resistance elements them operating in high voltage.

Today I can proudly say that I did succeed making something very special as verification box, this now giving me the opportunity to say that ITTSB Blog products testing workbench this is today one step further to completeness speaking of measuring standards’.
Testing of any insulation resistance tester this is now possible, and my own product reviews will deliver much higher value to my readers.

Vishay Foil Resistors brand and POWERTRON products acted to me as trigger, so me to dive in and begin knowledge hunting regarding this sector of products.
Nowadays I have the awareness that I got extremely lucky speaking of timing and place and even of planets position, because I got in contact with a resistance elements manufacturer whom using leading technology and this translate in to a market leader regarding such special products.
9) Several  Pictures gallery
Written by Kiriakos Triantafillou -  February 2017 ©

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