Standardization of the values   Notes practice on the fixed capacitors   Variable capacitators
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ELECTRONIC COMPONENTS 2        3rd part

  3. - IDENTIFICATION OF THE FIXED CAPACITORS

Each condenser is characterized by a marking which gathers the electric characteristics of operation expressed in the form of an alphanumeric code or colors like that of resistances.

According to international standards, more or less followed by the electronic component makers, each condenser must have following marking:

Rated capacity in pF, nF or F (the unit can be omitted), nominal Tension of service in volts, Tolrance on the value of the capacity in %, Sigle of the type of condenser, Sigle of the manufacturer, Date from manufacture.

The first two data (capacity and nominal tension of service) are always specified while the others it clearly or are not always indicated.

On the electrolytique capacitors, in addition to the initials of polarity, the allowed range of temperatures for their employment is deferred whereas the very broad tolerance misses.

Here some examples which one can find on the body of the components:

In light : 470 pF - 160 V - 5% ; 22 nF - 630 V - 10% In alphanumeric code : 470 J ; 022 K 630 code colors of Them : yellow, purple, maroon, green ; red, red, orange, white, blue In mixed code (alphanumeric and colors) : 470 J with red band ; 0,022 K with black band

The tendency today consists in eliminating from marking all that is not essential and keeping the most important data of the condensers. Many manufacturers thus eliminate from marking the symbols from the measuring units (pF, nF, F, V, %) as well as the zero which precede the comma or the point. In this case, however, the value of the capacity is always implied in microfarads.

For example, a condenser of 0,047 F - 630 V - 10% can be marked in the following way :

 Marking _des_condensateurs

When the tolerance of the condenser is of 20%, It is generally not indicated ; thus a condenser of 0,1 F.400 V. 20% can be simply marked .1 / 400.

Marking in alphanumeric code is very widespread, but it is of more difficult interpretation because it uses initials to indicate the data of the condenser : the tolerance and for the ceramic condensers: the temperature coefficient.

On figure 20, a table represents the code of marking of the ceramic, tubular condensers and with disc according to I.E.C. (International Electrotechnical Commission) which deals with the international standardization of the components produced by several industries.

Let us see now with some examples how it is possible to carry out the reading of this table below.

 Code_alphanumerique_des_condensateurs_ceramiques_tubulaires_et_a_disque

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1st example :

Marked condenser: 2K7 PG

One starts first of all with the value of capacity, which according to the multiplier K = 1 000 which constitutes the comma, will be of 2,7 x 1 000 = 2 700.

This value ranging between 1 000 and 10 000 will be expressed in pF, therefore the capacity of the condenser will be of 2 700 pF.

The two letters P and G respectively indicate the tolerances and the temperature coefficient.

The letter P, located in the first column of the table, corresponds to a tolerance from + 100 % - 0 % in the third column whereas the letter G (first column) defines the temperature coefficient -150 x 10-6 /C (fourth column) which can also be expressed by the N150 code.

One will thus have :

2K7 PG = 2 700 pF   ;   + 100 % - 0 %   ;   - 150 x 10-6 /C (N150) 

2nd example :

Marked condenser: 100 JN

100 indicates obviously the value of capacity expressed in pF (100 pF).

The letter J (first column) indicates the tolerance which is here of 5 % bus the value of the capacity is higher than 10 pF.

The letter N (first column) indicates finally the temperature coefficient (fourth column) equal here to - 750 x 10-6 /C (N750).

One will thus have :

100 JN = 100 pF 5 % ; - 750 x 10-6 /C (N750)

3rd example :

Condenser marked 4.7 BC.

4,7 is the value of the capacity in pF is 4,7 pF.

The letter B (first column) indicates the tolerance of the condenser: here 0,1 pF (second column) because the value of the condenser is lower than 10 pF.

The letter C indicates the temperature coefficient (fourth column) equal to 0. In this case, the condenser does not present any variation of capacity according to that of the temperature.

One will thus have :

4.7 BC = 4,7 pF 0,1 pF ; (NP0)

In the table of figure 21 is given the code envisaged by standards EIA (Electronic Industries Association) for the ceramic condensers to disc.

Some examples are deferred below for a correct interpretation of code EIA.

 Marquage_des_condensateurs_ceramiques_a_disque

1st example :

Condenser marked .1 MUIG

Inscription .1 indicates the value of capacity in F bus according to what was known as previously, initials .1 represents the value 0,1 F.

The capital letter M (first column) indicates the tolerance which will have to be read in the third column, since the value of the capacity is higher than 10 pF ; it will thus correspond to 20 %.

Initials UIG (seventh column) correspond finally to the temperature coefficient - 80 x 10-6 /C, read in the eighth column.

One will thus have :

.1 MUIG = 0,1 F (100 nF) 20 % ; - 80 x 10-6 /C

2nd example :

Condenser marked 6p8 D COG.

The inscription 6p8, where the letter p replaces the comma, indicates the capacity of the condenser expressed in pF, which is thus of 6,8 pF.

The letter D (first column) indicates the tolerance which will have to be read in the second column because the condenser has a capacity lower than 10 pF : 0,5 pF.

Lastly, initials COG (seventh column) indicate a null temperature coefficient (eighth column). In this case also, the variation in temperature does not determine any change of the capacitive value.

One will thus have :

6p8 D COG = 6,8 PF 0,5 PF; (COG = 0)

In the table of figure 22 is deferred a code of marking very much used by the Japanese manufacturers and who relates to not only the ceramic condensers but also the condensers out of polyester. Its reading does not present a particular difficulty, because it is enough to remember that the third figure indicates the number of zeros to add to the first two digits to reconstitute the value of the capacity whereas the letter indicates the tolerance.

Marquage_des_condensateurs_ceramiques (1) .gif

The examples deferred in the table above are enough to explain marking.

The table of figure 23 which is in bottom of this page refers to another code, used to mark the ceramic condensers and polyester ; as one can note it, it is about a code entirely made up by bands of colors. To be able to use it, it is first of all necessary to define the shape of the condenser one has.

One locates it on the drawings deferred above it table to determine the band of color which corresponds to the column in question.

Let us see now some examples of application of this code by knowing that the second column relates to only the ceramic with disc and tubular condensers and the seventh column only those with polyester.

 Code_couleurs_condensateurs_ceramiques_polyester

1st example :

Condenser polyester marked with the colors red - purple - orange - black - yellow.

1st band : red (1st column) = 2 (3rd column),

2nd band : purple (1st column = 7 (4th column),

3rd band : orange (1st column) = x 1 000 (5th column).

One obtains as follows :

27 x 1 000 = 27 000 pF 

4th band : black (1st column) = 20 % (6th column) bus C = 27 000 PF (> 10 PF). The graphic symbol > means larger than whereas the symbol indicates lower or equal to.

5th band : yellow (1st column) = 400 V (7th column).

One will thus have :

27 000 pF (27 nF) 20 % - 400 V

2nd example :

Ceramic condenser pipe marked with the colors chestnut - orange - white - black - green.

1st band : chestnut (1st column) = - 33 x 10-6 /C (2nd column),

2nd band : orange (1st column) = 3 (3rd column),

3rd band : white (1st column) = 9 (4th column),

4th band : black (1st column) = x 1 (5th column).

One thus obtains :

39 x 1 = 39 pF

5th band : green (1st column) = 5 % (6th column ; C > 10 PF).

One will thus have :

39 pF 5 % ; - 33 x 10-6 /C

3rd example :

Ceramic condenser with disc, marked with the colors : black - blue - gray - white - chestnut.

1st band : black (1st column) = 0 (temperature coefficient, 2nd column),

2nd band : blue (1st column) = 6 (3rd column),

3rd band : gray (1st column) = 8 (4th column),

4th band : white (1st column) = x 0,1 (5th column).

The value will be thus:

68 x 0,1 = 6,8 pF 

5th band chestnut (1st column) = 0,1 pF (6th column; C 10 pF).

One will thus have :

6,8 pF 0,1 pF ; (null temperature coefficient).

For the polystyrene condensers, one uses the code of the colors and literal deferred in the table of figure 24.

Code_mixte_et_couleur_des_condensateurs_polystyrene

The interpretation of this code does not present a particular difficulty because the value of the capacity is expressed in pF, the tolerance and the tension of insulation (only for the condensers of 1 000 Vncc) is indicated in light.

The letters which appear in the first column refer to the tolerance of the component when it is not indicated in light, while the possible band of color (2nd column) relates to the tension of service when it is different from 1 000 Vncc.

The examples deferred in the table are sufficiently explicit for the interpretation of the code.

Let us see now how one must consider the data deferred in the table of figure 25 used by certain manufacturers to mark the condensers of the ceramic type.

Code_mixte_couleur_des_condensateurs_ceramiques

These condensers present a band of color on the top of the body indicating the temperature coefficient (3rd and 4th column). The value of the capacity is registered in light on the body of the component, the letter p or n replaces the comma respectively to indicate the pF or the nF.

Let us see some examples :

P68 = 0,68 pF,

4p7 = 4,7 pF,

33p = 33 pF,

n15 = 0,15 nF = 150 pF,

2n2 = 2,2 nF = 2 200 pF,

39n = 39 nF.

For better realizing of the method adopted for correct interpretation of the code, one can see the examples deferred in the table of figure 25.

On figure 26, one indicated the code used for the marking of the electrolytique capacitors to tantalum.

Code_couleur_condensateurs_electrolytiques_au_tantale

To interpret the code suitably, it is necessary to direct the condenser well while referring at the point of color which informs about the polarity of the component (7th column).

This point indicates the multiplier (4th column) which it is necessary to use to establish the correct value of the capacity indicated by the bands of color corresponding to the first, second and third column.

The examples deferred in the table are sufficiently explicit, but it should however be specified that certain manufacturers of this type of condensers adopt marking in light.

HIGH OF PAGE 3. 1. - STANDARDIZATION OF THE VALUES

Like resistances, the condensers do not exist in all the values and the manufacturers, for economic reasons and of convenience, produce these components in series of value which it is advisable to know.

The values of the condensers of current production are called standardized values standards or values.

In the trade, we find easily and at a moderate cost these values of component. Each manufacturer chooses his own series of values standardized according to the possibilities of production and the request. One however seeks to eliminate this tendency while standardizing, on the national and international scale, of the series of values to facilitate the maintenance of the apparatuses of all marks and to make the production more economic.

Formerly, the decimal series was very much used to express the value of resistances or the condensers: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or 1 000, 2 000, 3 000 (in ohms for resistances, picofarads for the condensers). This series of values presented a disadvantage however, especially with regard to covering between a value and the following one for a precise tolerance.

Currently, one tends to manufacture resistances and condensers with other series of value as the table of figure 27 shows it.

Series_de_valeurs_normalisees_des_resistances_condensateurs 

These series are called (according to standard I.E.C.) E6, E12, E24, E48 because the values included/understood in one decade (between 10 and 100) are respectively 6, 12, 24, 48 ; actually, the values are given by a geometrical continuation (mathematics) of reason :

 Geometrique_de_raison_10

It is noticed that according to the percentage of tolerance, one obtains face values more or less: the narrower the tolerance is, the more the choice of existing values in the series is large.

There are other continuations of values reserved for a more specific use (professional): the series E96 (tolerance 1%) and the series E192 (tolerance 0,5%) which include/understand 96 and 192 face values per decade.

HIGH OF PAGE 3. 2. - NOTES PRACTICE ON THE FIXED CAPACITORS

During the replacement of a condenser, it is imperative to take account not only of the value of the capacity but also of the tension of service. Indeed, one will be able to replace a condenser by another having a higher tension of service with the same value of capacity but not the reverse. For example, a condenser of 100 nF / 25 V can be replaced by another of 100 nF / 50 V if the place allows it.

The electrolytique capacitors must be stored in a dry and fresh room (t 25) in order to prevent that they dry (loss of the electrolyte). If the period of storage were particularly long, it is advised to reform them before use. This treatment consists in subjecting the condensers, during a few minutes, with a tension continues lower than that of service marked on the case of the component (approximately half).

As for resistances, it is possible to resort to the connections series or parallel of several condensers to obtain values of capacity and given tensions of service.

In a series connection of condensers, it should be known that the tension of service of each condenser is added.

Thus for example, if we have three of the same condensers value 3,3 nF / 250 V assembled in series, the total tension being able to be supported by the grouping is of 250 V x 3 = 750 V with an equivalent capacity of 1,1 nF (3,3 nF / 3).

But it should well be remembered that by making a connection in series of of the same condensers face value with broad tolerances and different resistances of escape (example: electrolytique capacitors), the tension applied to the grouping series is not divided in parts equal at the boundaries of each condenser. It is thus desirable to stick to a maximum tension equal to the tension of the weakest service. It is advised for that to always connect in parallel on each series condenser (electrolytic especially), a resistance of high value in order to ensure a distribution equal of the terminal voltage of the two condensers (figure 28).

Repartition_tension_aux_bornes_de_2_condensateurs

HIGH OF PAGE 4. - VARIABLE CAPACITATORS

The variable capacitators differ from fixed by the fact that one can modify their capacitive value by means of a mechanical movement (in general, by rotation) ensured by a control shaft.

A variable capacitator is formed by a part fixed, called stator, and by a moving part called rotor ; these two parts are electrically isolated one from the other by dielectric.

While turning the moving part, one varies the capacity of the condenser of the maximum value to the minimal value or conversely. When the mobile blades which constitute the rotor intercalate between those which are fixed for him and which constitutes the stator, one obtains the maximum capacity of the variable capacitator. Contrary, when the mobile blades left the stator, one obtains a residual capacity which depends on the mechanical system.

The shape of the blades is particularly important because it influences much the characteristics of the condenser.

Figure 29 illustrates the various laws of possible variation (capacity, wavelength, frequency) of the variable capacitators according to the position of the mobile blades compared to those which are fixed.

 Differentes_lois_de_variations_des_condensateurs_variables

Figure 30 below represents a variable capacitator with air with only one cage. It is consisted a group of mobile metal blades interdependent of a control shaft which constitute the rotor. This one is connected electrically to the frame while the stator is insulated from it by a ceramic support. The value of the capacity varies between 10 pF and 500 pF and in the receivers of radio operator currents, the variable capacitator are with two cages (or double). The capacity of the two cages can be identical or different one from the other according to requirements' which vary from one receiver to another.

 Condensateur_variable_a_air_avec_une_cage

On the figure 31-a, the type of condenser is represented which has two sections equal with a variable capacity of 15 pF to 450 pF.

For the condensers of the type running, the swing angle of the control shaft is approximately 180 whereas others have a reducing gear (figure 31-b) which makes it possible to carry out a swing angle of the control shaft higher than 500, one thus obtains a highher degree of accuracy of the capacitive value.

 Condensateurs_variables_a_air_avec_2_cages

Sometimes certain variable capacitators have adjustable tangents which make it possible to vary the minimum capacity in some limit. These adjustable tangents are small variable capacitators called trimmers.

The trimmers are regulated only at the time of the debugging run of an apparatus and this procedure bears the name of taring.

There are also condensers butterfly (figure 32-a) which are generally not used in the current receivers and which have maximum capacities of 6 pF, 10 pF and 20 pF.

For particular circuits, one needs sometimes condensers with three cages (figure 32-b) with equal or different capacities according to needs.

Condensateurs_variables_a_air_pour_usages_speciaux

In the receivers of radio portables and transistorized, the miniature variable capacitators find a broad employment; they are also called condensing with dielectric mixed, bus between the reinforcements and solid insulating material (generally out of polythene), there exist always spaces of air ; therefore, the dielectric one consists of polythene and air.

On the figure 33-a a miniature variable capacitator with going air with a capacity of 4 pF with 124 pF is illustrated ; for the two sections (cages), the dielectric one used is polyethylene. The variable capacitator with dielectric solid deferred on the figure 33-b is of larger size and has a section (cage) whose capacitive value lies between 8 pF and 130 pF whereas other A a capacity being located between 7,5 pF and 39 pF.

Condensateurs_variables_miniatures

HIGH OF PAGE 4. 1. - TRIMMERS 

The trimmers are adjustable condensers used separately or in parallel with the variable capacitators for the adjustment (taring) of the apparatuses.

They are carried out with the dielectric ones with air, the mica or out of ceramics.

On the figure 34-a, a trimmer with air from 1,5 to 30 pF with adjustment by screw is represented, on the figure 34-b, are on the other hand illustrated two trimmers with leather of value identical 1,5 to 30 pF assembled on a support adapted by a mechanical fixing.

 Condensateurs_Trimmers

The trimmer with the mica represented on the figure 34-c, has a variation of larger capacity, ranging between 10 pF and 150 pF.

On the figures 34-d, 34-e and 34-f, are illustrated three ceramic types of trimmers, characterized by reduced dimensions and a weak variation of the capacity (2 to 8 pF) ; one uses them in the circuits high frequencies. These trimmers is adjusted thanks to a screw which one actuates with a small screwdriver (figures 34-d and 34-f) or while making slide a sleeve along the body of the condenser (figure 34-e).

 

     

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