Classification of resistors by materials used and production technology

Depending on the material of the conductive layer and on the production technology, both the general (standard) characteristics of the resistor and its special, specific properties depend, which mainly determine the area of ​​use of this type. In order for the reader to approach the selection of the resistor type consciously and purposefully, this section gives a brief description of each type of the most common resistors with an explanation of their names.

Thus, PERMANENT CARBON AND BORON RESISTORS

In carbon resistors, the conductive layer is a film of pyrolytic carbon. These resistors have high parameter stability, small negative temperature coefficient of resistance (TKS), they are resistant to impulse loads.

Boron-carbon resistors are distinguished by the fact that they contain a small amount of boron in the conductive layer, which makes it possible to reduce the TCR. There are several types of resistors, the names of which are deciphered as follows.

VS — high stability;

OBC — increased reliability,

ALL — with axial wires;

ULM — lacquered carbon with small dimensions;

ULS — special lacquered with carbon;

ULI — measuring instruments with varnish coating;

UNU-Unshielded Ultra High Frequency Carbon Rod;

UNU-Sh-ultra high frequency washers without carbon protection;

IVS — pulse with high stability; BLP — boron-carbon lacquered precision (with the lowest level of internal noise — no more than 0.5 μV / V).

PERMANENT METAL FILMS AND METAL OXIDE RESISTORS

The conductive element for resistors of this type is an alloy or metal oxide film. They have a low noise level (not more than 5 μV / V), good frequency response and are resistant to temperature changes. Temperature coefficient of resistance these resistors can be positive or negative. These are the main types:

MLT-heat-resistant varnish lacquered with metal film;

OMLT — increased reliability; MT-heat-resistant metal-film;

MUN-ultra high frequency metal films, unprotected;

MGP — Metal Film Sealed Precision;

MOU-Ultra High Frequency Metal-Film;

MON — low resistance metal oxide (complements the MLT resistor rating scale);

C2-6 — metal oxide;

C2-7E-low resistance metal oxide (complements the range of MT resistors).

PERMANENT COMPOSITE RESISTORS

The conductive layer of composite resistors is a compound of graphite or carbon black with an organic or inorganic bond. Such connections make it possible to obtain conductive elements of any shape in the form of a solid body or film deposited on an insulating base. Resistors are very reliable.

Disadvantages of composite resistors include the dependence of resistance on applied voltage, noticeable aging, a relatively high level of internal noise, and the dependence of resistance on frequency.Resistors are available in the following types: composite bulk

C4-1 — increased heat resistance on an inorganic connection;

TVO-heat-resistant, moisture-resistant, voluminous with an inorganic bond;

KOI — with organic binder;

composite film

KIM — composite insulation for small-sized equipment;

KPM — small-sized composite lacquered;

KVM — composite vacuum (in a glass cylinder),

KEV — High Voltage Composite Screen.

PERMANENT WIRE RESISTORS

The conductive element of resistors is a wire or microconductor wound on a ceramic base. Resistors are available in the following types:

PKV - ceramic-based, moisture-resistant, multi-layer groups I and II (group II resistors are designed for operation in dry and humid tropics)

PTMN — small size multilayer nichrome;

PTMK-multilayer constantan with small dimensions

PT — precision wire;

PE — enameled pipe, moisture resistant;

PEV — moisture-resistant enamelled pipe;

PEVR — enamelled tubular moisture resistant adjustable;

OPEVE — increased reliability and durability;

PEVT-heat resistant moisture resistant (tropical);

All wire resistors are recommended for use in AC and DC circuits with a frequency no greater than 50 Hz.

Here it will be appropriate to bring some clarity on the issue of designation of resistor types. The fact is that today a radio amateur, buying resistors, can encounter two systems of designation of the type (do not confuse it with the rating and tolerance marking, which will be discussed further). One of them is older, the other is new, operating today.

In the old system, the first element was designated as follows:

C — constant resistors; SP — variable resistors; ST — thermistors; CH — varistors.

The second element, as in the new system, was digital, but with more detailed details on the type of resistive element material (1 — carbon and boron-carbon, 2 — metal-dielectric and metal oxide, 3 — composite film, 4 — composite bulk, 5 — wire).

Simultaneously with these two, there is an even earlier one - the letter system, in accordance with which the absolute majority of resistors installed in internal radio equipment from the 70s and 80s are marked.

When buying resistors, you need to be very careful in choosing their type, based not on appearance (especially foreign-made resistors!), but on the special properties determined by the function of this resistor. Significant help in this approach can be provided by the above list of the main properties of different groups of resistors, depending on the material of the conductive layer and their production technology.