ELECTRICAL PARAMETERS

Resistance Values

E6 and E12 values are available as standard.

Resistance Tolerance

± 20% and ± 10% available as standard.

Resistivity Range - ρ

10 Ohm cm to 5000 Ohm cm

ρ = R x A/L,   where R = Resistance Value

Temperature Coefficient - TCR

-0.05% to -0.15% per °C Temperature Rise depending on Resistivity Value.

TCR = 0.16 x e -(log ρ / 1.4) - 0.135     (% / °C Temperature Rise)

Voltage Coefficient - VCR

-0.5% to -7.5% / kV / cm

VCR = -0.62 x ρ 0.22   (% / kV / cm)

For ρ domain 10 to 5000 Ohm cm

Inductance

This is negligible (nH) and the Resistors may be described as non-inductive. In practice the inductance of connecting leads will be greater than that of the Resistors.

Maximum Working Voltages

The Maximum Working Voltage levels (V working) can be derived from the appropriate formulae for each Resistor Type.

Waveforms are defined in the usual manner: 1.2/50 µs indicates a rise time to peak value in 1.2 µs and an exponential decay to half amplitude in a total time of 50 µs.

 Worked example (50 Hz rms) : Consider an SR 2825 Resistor with a Resistance Value of 100R0. What is the maximum 50 Hz rms Working Voltage (kV) sustainable for an insertion time of 100 ms? V working = 2.4 x (1.8R / t) 0.3 = 2.86 kV (Note: R = Resistance Value in Ohms and t = 50 Hz Insertion time in ms) Worked example (1.2 / 50 µs) : Consider an SR 2825 Resistor with a Resistance Value of 100R0. What is the maximum Working Voltage (kV) for a 1.2/50 µs waveform? V working = 1.26R x (-1 + √(1 + 33/R)) = 19.31 kV

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