Cable Factors
The following data may be used to calculate the approximate finished diameter of a multiconductor cable if you know the diameter of the individual component. These charts are based on the assumption that the cable consists of identical components and that they are cabled or assembled in a concentric manner. For example, cables consisting of seven conductors 22 AWG or seven twisted pairs 22 AWG, both have a multiplying factor of 3.0, but the component diameter of the pair will obviously be larger than that of the single conductor.
First use the number of components to find the correct multiplying factor. This factor times the diameter of a component equals the diameter of the cable core under the cable jacket. If the cable is shielded, an extra .010" should be included. Next use the jacketing chart to determine the typical overall jacket wall thickness. Adding the cabled core diameter and twice the overall jacket wall thickness equals the required finished cable diameter. For example, suppose we wish to estimate the diameter of a cable that consists of twelve conductors 18 AWG, Irravin B with an overall shield and jacket. The component wire has a diameter of 0.069", times the multiplying factor of 4.15 equals a core diameter of 0.286". Adding another 10 mils to cover the shield brings the core dimension to 0.296". The overall jacket thickness for this core size is 0.045", so the estimated cable diameter is 0.296", plus 0.045", plus 0.045, or 0.386".
Typical Insulation Characteristics
The following chart should be used as a guide for the relative performance of insulation materials. Note that many special compounds have been developed that maximize a particular performance characteristic such as electrical or mechanical performance.
| No. of Components | Multiplying Factor | No. of Components | Multiplying Factor | Diameter of Core (Inches) | Overall Jacket Thickness (Inches) |
|---|---|---|---|---|---|
| 2 | 2.0 | 9-10 | 4.0 | 0.425 or less | 0.045 |
| 3 | 2.15 | 11-12 | 4.15 | 0.426-0.700 | 0.060 |
| 4 | 2.41 | 13-14 | 4.41 | 0.701-1.500 | 0.080 |
| 5 | 2.7 | 15-16 | 4.7 | 1.501-2.500 | 0.110 |
| 6-7 | 3.0 | 17-18-19 | 5.0 | 2.501-larger | 0.140 |
| Temp. c | Dielect. | Velocity | Resistance to: | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Insulation Material | Min. Max. |
Const.K | % | Ozone | Flame | Moisture | Oil | Alcohols | Gasoline | Outgassing | Sunlight |
| PVC | -40 105 |
4-6 | - | G | G | G | F | G | P | P | G |
| Polyethylene | -55 80 |
2.15 | 66 | G | P | E | G | E | F | F | E |
| Crosslinked Polyethylene | -55 125 |
2.15 | 66 | G | G | E | G | E | G | F | E |
| Foamed Polyethylene | -55 80 |
1.65 | 78 | G | P | G | G | E | F | F | E |
| Rubber | -40 75 |
3-5 | - | P | P | G | P | G | P | P | F |
| Nylon | -55 115 |
- | - | G | G | F | E | P | F | F | E |
| PTFE | -70 260 |
1.95 | 70 | E | E | E | E | E | E | E | E |
| FEP | -70 200 |
2.0 | 70 | E | E | E | E | E | E | E | E |
| Foamed FEP | -70 200 |
1.65 | 78 | E | E | G | E | E | G | E | E |
| Polypropylene | -40 105 |
2.2 | 66 | G | P | E | F | E | F | F | E |
| Silicone Rubber | -80 150 |
3-3.5 | - | E | F | G | F | F | F | G | E |
| Kapton | -70 200 |
3.6 | - | E | E | G | E | E | G | E | E |
| Tefzel | -70 150 |
2.6 | 62 | E | E | E | E | E | E | E | E |
| XML-125 | -55 125 |
2.5 | 62 | G | E | G | G | G | G | G | G |
| Irravin | 105 |
2.8 | - | G | G | E | E | G | F | P | G |
| Exane | -55 110 |
4.5 | - | G | E | E | E | E | G | F | E |
Key:
E-excellent
G-good
F-fair
P-poor