How to Read a 6-Band Resistor
A 6-band resistor is a high-precision resistor that includes an additional colour band to indicate its Temperature Coefficient of Resistance (TCR). The first five bands determine the resistor's value and tolerance, while the sixth band indicates how much the resistance changes with temperature. These resistors are commonly used in laboratory instruments, precision measurement equipment, aerospace systems, medical electronics and other applications where temperature stability is important.
Band Functions
| Band | Purpose |
|---|---|
| Band 1 | First significant digit. |
| Band 2 | Second significant digit. |
| Band 3 | Third significant digit. |
| Band 4 | Multiplier. |
| Band 5 | Tolerance. |
| Band 6 | Temperature Coefficient (TCR). |
Colour Code Table
| Colour | Digit | Multiplier | Tolerance | TCR (ppm/°C) |
|---|---|---|---|---|
| Black | 0 | ×1 | — | 250 |
| Brown | 1 | ×10 | ±1% | 100 |
| Red | 2 | ×100 | ±2% | 50 |
| Orange | 3 | ×1,000 | — | 15 |
| Yellow | 4 | ×10,000 | — | 25 |
| Green | 5 | ×100,000 | ±0.5% | 20 |
| Blue | 6 | ×1,000,000 | ±0.25% | 10 |
| Violet | 7 | ×10,000,000 | ±0.1% | 5 |
| Grey | 8 | ×100,000,000 | ±0.05% | 1 |
| White | 9 | ×1,000,000,000 | — | 0.5 |
| Gold | — | ×0.1 | ±5% | — |
| Silver | — | ×0.01 | ±10% | — |
How to Read a 6-Band Resistor
- Read the first three colour bands as significant digits.
- Read the fourth band as the multiplier.
- Read the fifth band as the tolerance.
- Read the sixth band as the temperature coefficient (TCR).
Worked Examples
Brown Black Black Red Brown Brown 1 0 0 ×100 ±1% 100 ppm/°C 100 × 100 = 10,000 Ω = 10 kΩ ±1% TCR = 100 ppm/°C
Red Red Black Brown Brown Red 2 2 0 ×10 ±1% 50 ppm/°C 220 × 10 = 2,200 Ω = 2.2 kΩ ±1% TCR = 50 ppm/°C
What Is Temperature Coefficient (TCR)?
The Temperature Coefficient of Resistance (TCR) indicates how much a resistor's value changes with temperature. It is expressed in parts per million per degree Celsius (ppm/°C).
A resistor with a lower TCR changes less with temperature and provides better stability in precision circuits.
A 10 kΩ resistor with a TCR of 50 ppm/°C will change by approximately 0.5 Ω for every 1°C change in temperature.
Typical Applications
- Precision measurement equipment.
- Digital multimeters.
- Oscilloscopes.
- Medical instruments.
- Laboratory power supplies.
- Industrial automation.
- Aerospace electronics.
- Communication systems.
- High-end audio equipment.
- Calibration standards.
Reading Tips
- The sixth band is usually separated slightly from the first five bands.
- Most 6-band resistors have a brown or red tolerance band.
- Always identify the tolerance band before reading the resistor.
- Use a multimeter to verify the resistance if the colours are faded.
Common Mistakes
| Mistake | Solution |
|---|---|
| Ignoring the sixth band. | Remember it specifies the temperature coefficient, not the resistance value. |
| Reading from the wrong end. | Locate the tolerance band first. |
| Confusing multiplier and tolerance. | The fourth band is always the multiplier and the fifth is the tolerance. |
| Assuming all resistors are 4-band. | Precision resistors commonly use five or six bands. |
Testing
- Read the colour bands and calculate the expected resistance.
- Disconnect power from the circuit.
- Measure the resistor using a digital multimeter.
- Verify that the measured value is within the specified tolerance.
- Check the datasheet if temperature stability is important.
Key Points
- 6-band resistors are precision resistors with an additional temperature coefficient band.
- The first three bands represent significant digits.
- The fourth band is the multiplier.
- The fifth band specifies tolerance.
- The sixth band indicates how much the resistance changes with temperature.
- Low TCR resistors are preferred in precision measuring equipment and high-quality analogue circuits.