| From Norman H. Schneider, Electrical Instruments
and Testing (Spon and Chamberlain, New York, 1907) pp 27-8
" As in most cases it is not desirable to permit the entire current used in a test to flow through the galvanometer, part of it is shunted or caused to pass around the latter.
A shunt bears a definite ratio to the resistance of the galvanometer, being generally adjustable to 1/9, 1/99 or 1/999 of its resistance so that 1/10, 1/100 or 1/1000 part of the current only passes into the galvanometer.
The degree in which the shunt increases the range of deflection of a galvanometer is termed its multiplying power.
The current therefore in the galvanometer must be multiplied by the multiplying power of the shunt to show its true value in the circuit."
All three of these Ayrton Shunts are in the Greenslade Collection.
The 1911 catalogue of W.G. Pye & Co. of Cambridge, England, lists this as an Ayrton-Mather Universal Shunt, and notes that it "is far more useful than the ordinary pattern, as it is applicable to any galvanometer. The stock winding has shunt powers of 1000, 5000, 100, 50, 5 and 1. The total resistance is 10,000 ohms and the sunt is fitted with positions in which the galvanometer is "shorted" and "off." Fitted with copper coils --- £3.10.0"
The instrument is in the early apparatus collection of Case Western Reserve University in Cleveland,
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