Robust helical spring microbalance

An account is given of the construction of a simple null-reading microbalance which has been used for low-temperature magnetic susceptibility measurements and may have wider applications.

The device consists essentially of a helical ribbon spiral spring about ½ in. diameter and 12 in. long which supports a working load of about 40 g. The noise level under normal laboratory conditions is less than 2 μg and is achieved by a mechanical filtering action resulting from a suitable disposition of 20 g of the load. The apparatus is robust, inexpensive and easily constructed.