The range of standard resistors available is from 0.0001 ohm to 10,000 ohms.
constructional reasons these non inductive standard resistors have been divided into four
The units of each group are of similar mechanical design and
dimensions which have been determined with consideration for a common
upper limit for heat dissipation and current carrying capability.
The resistance material is manganin (Cu-Ni-Mn alloy). The
are built into cylindrical metal containers for oil immersion to ensure
uniformity of temperature, the 10 and 50 watt units are air cooled and
fitted with a hand operated mechanical oil stirrer.
The 200 watt units
are water cooled and provided with a pulley to drive the mechanical oil
The 500 watt standard
resistors are also water cooled but are fitted with a motor
drive of the stirrer.
The terminal arrangements provide for separate current and potential
terminals for use with a potentiometer or DVM.
The available standard ranges and electrical performance data are set
out in Table 1.
Modified resistance units can be quoted to meet
Dimensional and other details are shown in Table 2.
N.B. - These standards are not filled with oil when supplied.
recommended oil is Castrol Whitemor WOM14 or if not obtainable any high
quality non- corrosive oil can be used such as high quality Transformer