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Q&A
This is where you can refer to frequently asked questions.
Notation of resistance value and resistance tolerance (accuracy)
Resistance
mΩ notation | Ω notation | KΩ notation | MΩ notation | Notation using R | ||||
0.1mΩ | = | 0.0001Ω | = | = | = | R0001 | ||
1mΩ | = | 0.001Ω | = | = | = | R001 | ||
10mΩ | = | 0.01Ω | = | = | = | R010 | ||
100mΩ | = | 0.1Ω | = | = | = | R100 | ||
1000mΩ | = | 1Ω | = | = | = | 1R00 | ||
10Ω | = | 0.01KΩ | = | = | 10R0 | |||
100Ω | = | 0.1KΩ | = | = | 100R | |||
1000Ω | = | 1KΩ | ||||||
| 10KΩ | = | 0.01M | ||||||
100KΩ | = | 0.1M | ||||||
1000KΩ | = | 1M |
Resistance tolerance (accuracy)
Notation with % | symbol |
±0.005% | V |
±0.01% | T |
±0.02% | Q |
±0.05% | A |
±0.1% | B |
±0.25% | C |
±0.5% | D |
±1% | F |
±2% | G |
±3% | H |
±5% | J |
±10% | K |
±20% | M |
Definition of terms
Rated ambient temperature
The maximum ambient temperature of a resistor that can be used continuously with the specified rated load (electric power) applied. Note that this is the temperature around the resistor inside the device that incorporates the resistor, not the temperature of the air outside the device.
Rated power
The maximum value of power that can be continuously loaded at the rated ambient temperature.
Rated voltage
The maximum value of DC voltage or AC voltage (effective commercial frequency value) that can be continuously applied at the rated ambient temperature, and is the value calculated by the following formula using the rated power and nominal resistance value.
Voltage (E) = √(W ・ R)
However, the maximum working voltage shall not be exceeded.
Voltage (E) = √(W ・ R)
However, the maximum working voltage shall not be exceeded.
Critical resistance value
Maximum nominal resistance that allows the rated power to be loaded without exceeding the maximum working voltage.
At the critical resistance value, the rated voltage and the maximum working voltage are equal.
At the critical resistance value, the rated voltage and the maximum working voltage are equal.
Max. working voltage
The maximum value of DC voltage or AC voltage (commercial frequency effective value) that can be continuously applied to a resistor or resistance element. However, below the critical resistance value, the maximum value of the voltage that can be applied is the rated voltage.
Max. overload voltage
In the overload test (JIS C 5201-1 4.13), the maximum value of the voltage that can be applied for five(5) seconds or 10 seconds, which is the time specified by the individual product specification.
However, the voltage shall not exceed the specified maximum overload voltage.
Withstand voltage
In the withstand voltage test (JIS C 5201-1 4.7), the AC voltage (commercial frequency effective value) that can be applied for one(1) minute between the electrode and the designated point of the exterior.
Power Derating Curve
A curve showing the relationship between the ambient temperature and the maximum value of electric power that can be continuously loaded at that temperature, generally expressed as a percentage.
TCR
Within the operating temperature range of a resistor, the resistance will also change as the temperature changes.
The rate of resistance change per 1℃ is referred to as the Temperature Coefficient of Resistance(TCR).
TCR is available from a formula below.
R: Actually measured resistance value(Ω) at t℃
R0: Actually measured resistance value (Ω) at reference temperature
t: Actually measured test temperature（℃）
t0: Actually measured reference temperature (°C)
R0: Actually measured resistance value (Ω) at reference temperature
t: Actually measured test temperature（℃）
t0: Actually measured reference temperature (°C)
Temperature coefficient (ppm / °C) | symbol |
±1 | N |
±2 | R |
±3 | S |
±5 | U |
±10 | Y |
±20 | T |
±30 | L |
±50 | Z |
±100 | P |
±150 | J |
