Revisions can be basically divided into inspections of installations and switchboards, lightning conductors, tools and appliances and machines.

Each group has specific requirements for both the measured quantity and its measured value, which is considered satisfactory.
Their description is best found in the relevant standard.
For appliances, it is e.g.
ČSN 33 16 00, for machines ČSN EN 60204-1 and in the case of electrical installations e.g.
ČSN 33 2000-6.
The standards of the ČSN EN 61 557 series include requirements for test equipment (measuring instruments).

There are dedicated instruments for each measured quantity separately or multifunctional devices that are able to measure a large part or all of the quantities for a selected revision.

An example of the need for careful selection may be the fact that a large number of cheaper devices measure only basic quantities and do not allow other additional measurements at all or with difficulty.
A typical example is a simple and relatively inexpensive measuring device for checking electrical appliances, which can easily handle inspections of, for example, simple household appliances and hand power tools.
However, problems arise when it is necessary to inspect an appliance with a fixed connection (electric stove), three-phase appliance, welding machine and others.

A special group are inspections of medical appliances and devices, for example, according to the ČSN EN 62 353 standard.
Such measurements can only be carried out with certain measuring instruments or with the help of accessories that can be connected to standard inspection instruments.
However, performing revisions in healthcare can only be recommended to experienced revision technicians familiar with this issue.

This is an important figure.
If I perform occasional measurements and only some parameters, it is probably more advantageous to buy one or several cheaper single-purpose devices.
However, if I measure a large number of installations or appliances on a daily basis, it will probably be more advantageous to buy a universal multifunctional device.

A lot depends on your attitude here.
When using single-purpose and simpler devices, we must carefully write down the measured data.
Smarter devices have their own memory, in which they can store a different amount of data from measured values to the identification of the measured place, and some even details such as floor, room, appliance identification number.
This then rapidly reduces the need for paper records.
The best-equipped devices can connect, for example, a barcode reader or RFID reader and can connect to a computer, where a suitable program can then maintain the entire measurement database, measurement history and create a complete audit report.

This is often the first and decisive parameter.
However, these devices are not common consumer goods, so we should carefully consider whether cheaper devices will be sufficient for the planned use not only now, but also in the future, whether they comply with the relevant standards, etc.
Service and calibration are also important criteria.
(see one of the other points)
Low price should therefore not be the decisive criterion.
Think carefully before you buy a cheap device from a second-hand store, from a foreign e-shop or from an unauthorized seller.
You can easily lose the money you save later on due to service or calibration issues.
A device from a foreign e-shop may also not comply with our local standards and may not be usable for measurements in our country.
On the other hand, the high price of some devices is not due to their higher utility value, but often you pay for a brand or additional features that you really won’t use.

The basic parameter is the CE mark, or the product’s compliance with the requirements of EU regulations.
The safety of the device is ensured by compliance e.g.
with the ČSN EN 61010-1 standard.
Also, the device should comply with those of the above standards according to which it is supposed to measure.
This should apply to domestic manufacturers without exception.
In the case of devices from authorized importers, the importer is responsible for compliance with the standards and declares this by issuing a declaration of conformity.
Devices that have come to us in another way (private import, foreign e-shops, importers without manufacturer authorization, etc.) can be problematic.

All instruments have a defined basic measurement error.
This applies under precisely defined conditions, usually in the laboratory.
However, we will measure in the field in a wider range of temperatures, humidity, under fluctuating network voltage.
Under these conditions, the so-called
A measurement error that can be several times greater than the basic one.
In many cases, the minimum accuracy of the measurement is given directly by standards (e.g. ČSN EN 61557), but it is always good to take into account the circumstances of the specific measurement.
Of course, it is possible to buy a measuring device that measures with high accuracy and to many valid places, but its purchase and subsequent operation (service, calibration) would be unnecessarily expensive.

Service availability, price and speed is one of the most important criteria.
Given that more complex repairs of modern devices can no longer be carried out elsewhere than at the manufacturer, it is good to be interested in the manufacturer’s or importer’s approach to service, not only to repairs, but also to consulting services.
When purchasing a measuring instrument from abroad or through the so-called
It is possible to save a certain amount of gray imports, but the initial advantage can turn into a bitter disadvantage when it is necessary to repair or replace this device.
There may also be a problem with obtaining instructions for use.
Official importers devote a lot of time and resources to translating manuals, so they keep a good eye on their know-how.
The same applies to calibrations.
An inspection device must be calibrated and having a top-of-the-line device, but then travels for a month in Europe for repair or calibration, which only the manufacturer can do, may not be an advantage.
The calibration process can also include setting up the device, but it is necessary to know how to switch the device to the setting mode or to have the appropriate software.
In this respect, too, domestic manufacturers or official importers have a great advantage.