Dating vintage rotary watches

Northrup was a professor at Princeton and only stayed with Leeds for about seven years but his name remained with the company.

L&N was a major supplier of scientific instruments for colleges and universities, usually in the Physics Department.

These types of boxes were used in DC Resistance bridge circuits for precise measurements of an unknown resistance (Wheatstone Bridge circuits) or in other circuits for calculating current flow, low voltage levels or comparison evaluations.

Both of these Otto Wolff resistance boxes were used a Mount Wilson Observatory in Southern California. Wilson and the facility there had (has) a lot of very early test gear.

These would be thermocouples, RTDs and other temperature sensors or transducers.

L&N built precision resistance devices including decade boxes, various types of elaborate potentiometers, fixed resistances along with sensitive galvanometers, individual component-type Wheatstone Bridges and many other types of instruments.

Rogers Nov, 2014 These two precision resistance boxes were built in Berlin by Otto Wolff and date from around 1900. Biddle of Philadelphia imported these instruments and each box has his tag attached.

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L & N was purchased by General Signal Company in the mid-1990s. This L&N box differs from the "shunt-pin" type of R box in that the resistance value desired is just "dialed-in" with the switches. The hard rubber used in L&N equipment has a tendency to turn brown with long-term exposure to light. As can be seen from the property asset decal on the front, this instrument was used a Mount Wilson Observatory.Otto Wolff, from 1900 to 1909, produced the Reichsanstalt-type of resistance standards used at the National Bureau of Standards (NBS.) At the turn of the last century, many precision measurements had to be calculated because the measurement couldn't be made directly since many of the instruments we take for granted today hadn't been developed.A known precision resistance allowed one part of the equation to be selected and the remainder was then calculated.To select a R value one first has to know the total resistance of the box.In the case of the Central Scientific box shown, the total R is 1100 ohms.

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