A classic Weston style milliammeter was recently acquired at an antique store. The earliest patent date on it is 1894 and the latest date is 1901 so it is probably of 1901 or so vintage.
Since it is useful to monitor the current to my outdoor AM transmitter this meter was put to the task as shown here: http://postimg.org/image/66ljqt10d/ I mounted it on a wood stand such as was often done with such meters and it is connected in series with the DC feed to the remote transmitter. The full scale current is 100 mA but the transmitter draws 95 to 110 mA depending on the weather so it could read off scale but a 1 ohm shunt fixed the full scale current to 200 mA which is OK since what is watched for is a change in current indicating perhaps a problem.
In my early days in college and working in a motor/generator lab this type of meter was commonly used so there is some nostalgia for me.
It is noteworthy that when I checked the meter against my DMM the readings at 0, 50, 70, and 100 mA were exactly on the corresponding marks on the dial. Great craftsmanship back at the turn of the 19th to 20th century!
Some things are just done for fun.
Neil
A meter like that would make a centerpiece upon the altar of tower worship.
Very Nice
When they made that meter 111 years ago,
they were really serious it, I guess.
What a great picture!
Bruce
The distinctive shape of the meter case is due to the use of a large horseshoe magnet inside which is shaped pretty much like the Greek letter omega.
Vintage instruments used a finish called "Japan Black" as was done with this meter. This used to be the finish on old metal telephones. It is durable but a bit brittle as can be seen by some of the nicks in the picture. A little touch up could be done but this would spoil the originality of the meter so it will be left as is.
The terminal connections are on the back and are two brass 1/4" studs 2" long. These serve as the electrical connections as well as the mechanical mounting for the meter. The 2" length facilitates mounting on wood as done here or on another common panel material which was bakelite.
One failing though is the very narrow viewing window which allows a view of only the tip of the indicator. Modern meters expose most of the pointer to view which makes it very easy to read but this old type of meter can be read easily with some practice.
In the motor/generator lab mentioned earlier three such meters, volts, amps, and watts, had to be read within three seconds lest the heating due to the applied power change the motor characteristics. Reading three meters this quickly required a lot of practice but it remains a useful skill for reading a speedometer.
Neil
I always wondered why those early
meters were shaped like that. What
an interesting answer. A horseshoe
magnet.
Not too far back, I saw a picture of
a broadcast studio from 1925. There
were 3 or 4 meters there that looked
like your 111 year old find.
That's a serious looking set-up in the
picture.
Bruce