Direct current resistor 456

alternating currentAC/DCfor laboratory

Overview
The series 456 temperature-controlled fixed AC/DC resistors are available in five values: 10 Ω, 25 Ω, 100 Ω, 1 kΩ and 10 kΩ. They deliver high metrological performance through precise temperature control, oil filling and hermetic sealing, making them suitable for calibration and reference use in laboratory and industrial metrology.

Key features

• Nominal temperature coefficient of resistance: ±0.02 ppm/°C (temperature controlled between 18 and 25°C)
• Power: 0.5 W at 25°C
• Resistance tolerance: ±0.005%
• Current noise: < 0.010 µV (RMS) / V of applied voltage
• Thermo‑EMF: 0.1 µV/°C max, 0.05 µV/°C typical
• Protected against hostile environments, oil‑filled

Detailed description
Hermetically sealed, the 456 fixed resistors are protected against moisture and oxygen ingress, preventing long‑term degradation. The oil filling ensures effective thermal conduction and allows short overload periods without damage. With initial accuracy of ±0.005% and long‑term drift below 5 ppm, these resistors can serve as secondary standards for calibrating other instruments. Typical stability is 0.1 ppm/month or better.

Resistance generation (table)
Resistance values: 10 Ω / 25 Ω / 100 Ω / 1 kΩ / 10 kΩ
Stability: 1 ppm/year at 1 mA
Nominal temperature coefficient: 0.02 ppm/°C (temperature controlled between 18 and 25°C)
Tolerance (initial accuracy): ±0.005%
Inductance: 0.08 µH
Capacitance: 0.5 pF
Thermo‑EMF effects: 0.1 µV/°C max, 0.05 µV/°C typical
Noise: < 0.010 µV (RMS) / V of applied voltage

UKAS calibration uncertainties (k = 2)
DC resistance: 0.1 Ω to 1000 Ω → ±5 ppm (best extended uncertainties)
DC resistance: 1 kΩ to 100 kΩ → ±12 ppm
AC resistance: 2.5 Ω to 400 Ω (75 Hz) → ±15 ppm
AC resistance: 400 Ω to 1000 Ω (75 Hz) → ±100 ppm

General specifications
Dimensions (L x W x H): 144 x 110 x 96 mm (with housing)
Mass: 1 kg (with housing), 550 g (without housing)

Technical characteristics / specifications

• Model: series 456 (values: 10 Ω, 25 Ω, 100 Ω, 1 kΩ, 10 kΩ)
• Temperature coefficient: ±0.02 ppm/°C (18–25°C)
• Rated power: 0.5 W at 25°C
• Initial tolerance: ±0.005%
• Noise: < 0.010 µV (RMS) / V
• Thermo‑EMF: 0.1 µV/°C max, 0.05 µV/°C typical
• Inductance: 0.08 µH
• Capacitance: 0.5 pF
• Stability: 1 ppm/year at 1 mA
• Long‑term drift: below 5 ppm (typical stability 0.1 ppm/month)
• Construction: hermetically sealed, oil‑filled
• Holding temperature: 30°C ±0.1°C (other setpoints on request)
• Heater consumption: 2 W at 5 V
• Warm‑up time: ~30 minutes from 20°C to 30°C
• Indicator: temperature‑hold LED
• Housing dimensions: 144 x 110 x 96 mm
• Mass: 1 kg (with housing) / 550 g (without housing)
• Certification: UKAS calibration certificate (k = 2)