# [EVDL] N2HF Antique ampere hour meter



## EVDL List (Jul 27, 2007)

I have a Sangamo type N2HF ampere hour meter. I found two
references (below). It is marked 500 Amperes, 1250 Ampere-seconds
per disk revolution. Does anyone have any additional info
on this meter?

John in Sylmar, CA

From
http://www.watthourmeters.com/history.html

1904: Sangamo Electric Company, barred from making induction-type 
meters until Tesla's patent expired in 1910, introduces a new line of DC 
ampere-hour and watthour meters based on the mercury-motor ampere-hour 
meters widely used in England at that time. In an attempt to get back 
into the AC meter business, some of the DC mercury-motor watthour meters 
were redesigned for use on AC circuits. Although these meters were 
finicky and not as accurate as induction-type meters, they could easily 
be used on circuits of any commercial frequency from 25Hz to 133 Hz.

From
The Watthour Meter - Google Books Result
by Allen G. Jones - 1910

The Ampere-Hour Meter. The Sangamo ampere-hour meter, is now being used 
quite frequently in connection with the charging and discharging of 
storage batteries . . .

I found a description of the mercury-motor meters page 87-93 in the 
Jones book. (A Google search found the on-line copy of the book.)

John in Sylmar, CA
Driving on sunshine.

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