CIRSCALE AMPMETER, 1930's

Meter calibrated for measuring direct current up to 300 amps. Requires an external shunt.

Your comments:

• Cirscale ammeters and voltmeters had a very special movement designed to permit a full scale deflection of 300 degrees. They were unique products of The Record Electrical Co Ltd., Altrincham, near Manchester. A complete range of shunts was available for the portable ammeter. Fixed panel ammeters had shunts attached behind the panel. Cirscale ammeters could be ordered with a wide variety of scales ranging from 0-1 amp all the way up to 0-10,000 amps for use in power stations etc.
  .......... Dr Anthony Constable, Ealing, London, 29th of October 2010
  
  
• Additional comment to previous comment:
  
  On magnifying the image there appears to be a comment about a shunt resistance close to the 0 end of the scale.
  .......... John Webb, , 18th of March 2010
  
  
• I would query if this meter directly read 300A.
  The terminals at the front are entirely inadequate for this level of current or the cables that would be needed to carry such a current. I would expect an external 'Shunt' resistor to be used with the instrument connected across this and only taking a fraction of the total current.
  .......... John Webb, London Colney, ST ALBANS, 18th of March 2010
  
  

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