Vintage Chatsworth Standard Resistor / Resistance Colour Code Rotary Calculator

This is a highly colourful, pocket-sized, Vintage Chatsworth Standard Resistor / Resistance Colour Code Rotary Calculator, probably dating to the 1960s.

Approximate Size:

• Top: 5.2 cm
  
• Middle: 6.1 cm
  
• Bottom: 8.7cm

In fair condition, it comprises three rings of wood of decreasing sizes held together by a screw, each with a paper chart stuck on the ring marked with a scale in ohms. The smallest ring (top) is marked Spot, the middle ring, Tip, and the largest ring on the base marked Body.

Labelled: Chatsworth Resistance Chart

It was a quick way of working out the colour specification for various three band resistors in the workshop, now superseded by digital meters or online calculators, for example:-

Turning the circles so that the the rings read:-

• 50 ohms, (5 on the bottom ring, 0 on the middle ring, and ohms on the top), tells you that the resistor would have a green body, black tip and black spot / dot. 
• 25,000 Ohms (2 on the bottom, 5 on the middle, and 000 on the top), tells you that the resistor would have a red body, green tip and orange spot / dot

These results match those from a standard resistor colour code chart.

A nice little novelty which is also a useful tool!

Please click on the following link for more vintage tests / measures and meters