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Cropico RS3

Cropico RS3 Series

4 terminal construction, high stability resistance standard with wide range

- Wide range 0.0001 ohm to 1 Mega ohm
- Excellent load coefficient

Cropico RS3

The RS3 range of resistance standards are constructed using carefully selected low temperature coefficient Manganin or Zeranin wire, depending on the value, mounted on formers which have a high mechanical stability. The wires are wound in a strain free manner and heat treated to remove any stresses. They are also artificially aged under the strictest control. The result is a standard of high quality with long term stability and permanence of calibration combined with a low temperature coefficient.

The RS3 range also offers a high current carrying capability which makes them ideal for applications where precise current needs to be measured.

RS3 Specifications

Model Value Uncertainty of Adjustment @20°C Uncertainty of Certification Temp Coeff Typical 15 to 20°C Stability Over 1 Year 
RS3/001 0.0001Ω 0.02% ±200ppm 20ppm/°C 0.0025%
RS3/001 0.001Ω 0.01% ±50ppm 25ppm/°C 0.0025%
RS3/01 0.01Ω 0.01% ±25ppm 10ppm/°C 0.001%
RS3/02 0.02Ω 0.01% ±50ppm 10ppm/°C 0.001%
RS3/05 0.05Ω 0.01% ±50ppm 10pm/°C 0.001%
RS3/0.1 0.0.1Ω 0.003% ±25ppm 10ppm/°C 0.001%
RS3/1 0.003% ±25ppm 10ppm/°C 0.001%
RS/10 10Ω 0.003% ±25ppm 10ppm/°C 0.001%
RS3/25 25Ω 0.005% ±25ppm 10ppm/°C 0.001%
RS3/50 50Ω 0.005% ±25ppm 3ppm/°C 0.001%
RS3/100 100Ω 0.003% ±25ppm 3ppm/°C 0.001%
RS3/250 250Ω 0.005% ±25ppm 3ppm/°C 0.001%
RS3/1K 1kΩ 0.003% ±25ppm 3ppm/°C 0.001%
RS3/10K 10kΩ 0.003% ±25ppm 3ppm/°C 0.001%
RS/100K 100kΩ 0.003% ±25ppm 3ppm/°C 0.001%
RS/1M 0.01% ±25ppm 3ppm/°C 0.002%
Model Dissipation Max in Air Watts Dissipation Max in Oil Watts Max. I in Air (Amps) Max. I in Oil (Amps
RS3/001 1 4 100 200
RS3/001 1 4 32 60
RS3/01 1 4 10 20
RS3/02 1 4 7 14
RS3/05 1 4 4.5 9
RS3/0.1 1 4 3 6
RS3/1 2 10 1.4 3
RS/10 2 10 0.44 1
RS3/25 1 10 0.2 1
RS3/50 1 10 0.1 0.3
RS3/100 1 10 0.1 0.3
RS3/250 1 10 0.1 0.1
RS3/1K 1 10 0.03 0.030
RS3/10K 1 10 0.01 0.03
RS/100K 1 1 0.003 0.003
RS/1M 1 1 0.0002 0.0002
Value in ohms Typical time constant
+ 0.34μH/Ω
10Ω + 0.18μH/Ω
100Ω + 0.03μH/Ω
1kΩ + 0.04μH/Ω
10kΩ + 0.6μH/Ω

The resistance standards type RS3 were primarily designed as DC standards, however values above 0.1 ohm are non inductively wound and the adjacent AC characteristics are typical

Dimensions   Top Panel
160mm high x 90mm diameter approx  

Bakelite marked with the value, class designation and serial number

Mass   Case
0.9kg approx   Light alloy, black anodised to give maximum heat radiation Thermometer Tube: Slotted extending the length of the resistance element
Resistance Elemants   Label
Manganin or Zeranin depending on the value. 100 ohm, 1, 10 and 100 kilo ohm low inductance winding on brass formers with PTFE insulation. 0.1, 1 and 10 ohm bifilar winding on cylindrical brass formers with PTFE insulation. 0.01, 0.001, and 0.0001 ohm resistance material in the form of straight rods or loops supported on 12mm brass conductors  

Each standard is fitted with a label that describes its characteristic and operating parameters

Terminals   Maximum Continuous Working Voltage
Potential — Copper 4mm Current — Brass   70Vdc / 33vrms

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