There are bad dial indicators, there are good dial indicators, there are better dial indicators with higher resolution and then nothing comes ... and after that comes the Johansson Mikrokator. 

So simple in its construction, seemingly inconspicuous but still a perfect masterpiece, an ingenious flash of genius, an inventor's dream. The mikrokator is considered to be the very best mechanical length measuring instrument ever invented. It is robust, simple and very accurate.

By far the largest and almost the only manufacturer of the mikrokators over the years is the Swedish company CE Johansson, which began production of them in Eskilstuna in 1938 and continued until the company was bought up and went to the grave in the early 2000s.

The mikrokator quickly became a success and spread around the world to most countries. It is easy to state that CE Johansson and the mikrokator are intimately connected to each other, it is often called "Johansson mikrokator".

What is a mikrokator and what makes it so amazing?

Its construction means that it is absolutely free from backlash. Backlash is something all other mechanical pointing instruments have; they show slightly different dimensions depending on which direction you move the plunger (if the plunger is inward or outward). This is because the movement to the pointer in other instruments is transmitted by mechanical components such as gears that always have a little backlash. A mikrokator is not only free from turning, but it has also a completely frictionless mechanics.

A mikrokator can have a resolution of down to 0.05 µm, fantastically good on a mechanical instrument that was invented in the 30's! It also beats most digital measuring instruments today.

What is the secret?

Some may remember from when they were children that you can thread two sewing threads through the holes on a button and make the button spin by tightening the thread differently between the hands. A small movement where you tighten the thread makes the button spin very many turns. The small movement of the thread has been enlarged to a much larger movement of the button.

A mikrokator works in the same way. The button in the example above corresponds to the pointer which in a mikrokator is super thin and actually consists of glass. The pointer in a mikrokator moves about half a turn between the end positions. The sewing thread corresponds to two twisted thin metal threads.
The movement that is created comes from a plunger that is suspended without friction and affects how tightly the wire becomes. The measuring range is very small, somewhere between a few µm up to 100 µm.

The mikrokator is a type of comparator, which means that it compares the length of two different parts against each other. It must have a reference measure in the form of, for example, a gauge block (also an invention by CE Johansson) to compare with the object you want to measure. It can thus not directly say that a detail is x number of mm long.

If you want to measure something that is, for example, 30 mm long, you set up the mikrokator in a stand and reset the meter to a gauge block of 30 mm. Afterwards, you place your object you want to measure and read on the mikrokator how many µm larger or smaller the detail is compared to the gauge block. You thus know exactly how big your detail is. The prerequisite for this to work is that the reference – the gauge block – is calibrated so you know its exact dimensions.

You can also use it to compare two equal objects of unknown length against each other to see how big the difference is between them. The mikrokator is thus used to control small differences in length very precisely.

The mikrokator is robust and you should be able to drop it on the floor with the plunger down without it breaking. In any case, it is said so, I have not tested myself and probably think you should not, because every time a CE Johansson mikrokator breaks, there is one less in the world.

The mikrokator’s heyday may be over but there are still a lot of CE Johansson left out there who are used daily and still do a really great job! There are some other manufacturers today that manufacture and sell mikrokators of different qualities and with different price levels. However, it will never be a really big product like it once was. The mikrokator has in many cases been replaced by newer instruments, often digital and easier to use.

A call to all you lucky holders of one of the masterpieces of length measuring instruments is:

Take care of it, but without exaggerating! If you just keep it clean and tidy, it will surely give you many years of joy in the form of good and stable measurement values. And as with all measuring instruments, send it for calibration at regular intervals so you are sure that everything is as it should be and that it really shows exactly right! There is still no one who knows how old a CE Johansson mikrokator can get!

P.S. If you have any questions or need any help, please send inquiries to This email address is being protected from spambots. You need JavaScript enabled to view it.

Erik Stenström