Saturday, 3 March 2012

 Portable meters have been in use for over 100 years. Unlike many of today's digital multimeters that can measure ac and dc volts, resistance, current, capacitance, temperature, and more in a single, small handheld device, early portable meters were usually designed to perform only one measurement. A large number of the meters you will find that were manufactured before 1900 were fairly large. Many of these early meters were 6 or more inches in diameter. Portable versions were the same meter mounted on a wooden board and had a fitted leather or wood case. In the early 1900s, portable meters decreased in size and multiple functions were introduced.
Polarity indicators
One of the earliest portable devices I have in my collection for electrical measurements is a "Polarity Indicator." It was manufactured by the Manhattan Electrical Supply Company (MESCO) and patented in 1905.
This unique device is a small liquid-filled glass tube encased in a rubber type housing. It has two windows with a small binding post on each end. When hooked up across a dc circuit the liquid on the negative end will glow red. There is a metal sleeve that can be rotated to cover the glass windows when carried in your pocket. The MESCO Polarity Indicator was available in two models: model 3220 for battery circuits and a model 3221 for 50 to 600 Vdc. I have not been able to find out specifically what type of circuits these were used to test, but I would guess by the patent date they were used for checking polarity on telegraph circuits. I have actually hooked up one of them in my collection and found it still works after over 100 years. At auction, these usually sell for between $30 and $50.
Pocket watch meters
I regularly receive value inquiries about small meters the shape and style of a pocket watch. Since homes were not wired for electricity until the late 1920s, most early radios manufactured for use in the home or on farms were battery powered. Many of these early vacuum tube radios used several dry or wet batteries. Due to the high current requirements of vacuum tubes, these early radio batteries needed to be recharged or replaced on a regular basis. 
Companies like Hoyt, Sterling, Ever-Ready, Readrite, and others produced thousands of these pocket-watch-sized meters for testing radio batteries at home. These meters were a necessity for finding dead cells and knowing when to recharge or replace batteries to prevent the radio from dying during your favorite evening radio show. Most of these were the size of a typical pocket watch and many used the same watch style case. The meter would read dc volts, amps, or a combination of both.
To check a battery, a fixed test point on the bottom of the meter would be touched to one battery terminal and a short cloth covered test lead attached to a stem at the top would be touched to the other battery terminal. Due to the number of these produced and it's ability to be tossed into a drawer and forgotten about, this type of meter is quite common even today and can be frequently found at estate sales, auctions, and swap meets. The plain style case like the Sterling shown above has little value and may often found for $8 or less. The meters that actually resemble a pocket watch case usually have more value to collectors and will sell for $20-$30 or more depending on condition, style of printing on the meter face, and if the original box and instructions are included.
1930s: Portable service meters
By the early 1930s home radio service was in full swing. Servicemen needed portable equipment for servicing radios and electronic equipment in the field. Several manufacturers began to produce portable and handheld meters that measured ac and dc volts, resistance, current, and even capacitance. 
Some of these meters were small enough to hold in one hand, but many were still large enough to require a carrying handle. Pictured above is an early Hickok meter that measured dc volts and resistance. Most early Hickok test equipment from the 1920s and 1930s has value to collectors. It's not uncommon to see single pieces of early Hickok equipment selling for well over $100 even though it is only wanted for display.
Supreme Instruments was also a popular manufacturer of test equipment in the 1930s. They produced several models of service grade portable meters. Their earlier portable meters were housed in oak cases. Unlike other manufactures, Supreme trained it's assemblers to assemble one instrument from start to finish. It is not uncommon to find a name written in pencil on the inside of an early cabinet.
Supreme's 1934 line of test equipment included one of these portable meters. The Supreme model 222 "Multometer" measured ac and dc volts, milliamps, ohms, and capacitance.
The Multometer like other early meters did not use switches or buttons to select ranges. Each range was brought out to a pin jack and ranges was selected by moving the test lead from jack to jack. 
The Supreme Multometer is a rare find and looks to have been produced for only one year as it does not appear in their 1935 catalog. Later portable models were referred to as multi-meters, a term that still describes many meters today. Since surviving examples of the Supreme Multometer are scarce expect to pay at least $100.00 or more for a Multometer in good cosmetic condition.
Automobile service kit
One of the largest manufacturers of early meters was the Weston Electrical Instruments Co. of Newark NJ. Weston produced meters for just about every industry in the first half of the 20th century. Its 1916 model 280 volt-ammeter kit for testing early automobile electrical systems was popular in early garages. It included a leather carrying case with a fan-type meter and three shunts for current measurements. The shunts for making current measurements covered 3, 30, and 100 A.
The meter assembly itself was housed in a steel case with a bakelite base. The meter had four binding posts and scales covering 3, 30, and 300 V. A 46-page manual with hook-up diagrams was also included discussing every type of auto electric test the kit could do. Although this kit is still in good working condition, its value would be based on finding a collector wanting to add it to his automobile test equipment collection. I have seen a few of these at auction. A complete set in good condition with the original 1916 manual should sell for $25 to $55. 
These are only a few of the thousands of portable meter models produced before World War II. Although many still function, values of these earlier meters are based on the condition and design. The more art and detail used in the design of these meter faces and identifying plates, the more value they have to collectors
filed under: ,

0 comments:

Post a Comment

Heaven Of Professional Bloggers:JOIN HERE

Related Posts Plugin for WordPress, Blogger...
Copyright © 2013 Technodhuniah:Information Technology|Powered by Blogger