The 4-Ratio P.O. Box has sixteen coils as above and two proportional arms each with coils of 1, 10, 100, 1000, ohms.
Also incorporates infinity gap.
Two spring keys having good contact for battery and galvanometer is also provided.
The 3-Ratio P.O. Box has sixteen non-inductively would coils 1, 2, 2, 5, 10, 20, 20, 50, 100, 200, 200, 500, 1000, 2000, 2000, 5000 ohms and two proportional arms each with coils of 10, 100, 1000, ohms.
Resistance between 0.1 and 1111000 ohms can be accurately measured using a DC battery.
The whole system is contained in a superior quality wood box.
Available in 3-Ratio and 4-Ratio.
P.O.Box 3-Ratio and 4-Ratio (Manganin coil) consists of 12mm & 14mm thick rectangular brass block and have accuracy ±0.05%.
P.O.Box 3-Ratio and 4-Ratio (Constantan coil) consists of 12mm & 14mm thick rectangular brass block and have accuracy ±0.1%.
