Sangamo Electric Co. (1899-1975)

Gutmann Type A (Single Phase)

(1899 to 1901)
The Type A meter was based on a prototype developed by Ludwig Gutmann and refined into a usable form with the help of R.C. Lanphier, and was different from other meters of its time. A spirally-slotted cylinder was used to achieve the required space and time displacement needed to make the rotor move. The U-shaped voltage coil straddled the lower part of the cylinder and the current coil (which was wound on porcelain spools) was positioned on opposite sides of the upper part of the cylinder. A disk was riveted to the bottom of the cylinder and was used for braking as in other meters. The pivot was formed on the end of the rotor shaft and if it wore down, the whole rotor had to be replaced. Full-load adjustment was accomplished by moving the magnet, the light load adjustment was a laminated iron core that moved up and down within the cylinder, and there was no power factor adjustment on this meter.
Photo: Yardstick for Power: 50 Years of Sangamo Meters

Gutmann Type B (Single Phase)

(1901 to 1903)
The Type B was functionally identical but a much more compact version of the Type A. A single spirally-slotted disk was used instead of the large cylinder/disk assembly used in the Type A. The voltage and current coils were positioned side by side on a radial axis between the shaft and the edge of the disk to get the space and time displacement needed to make the disk turn. The cover on this meter was either cast aluminum or glass with an extension on front to make room for the disk and was sealed at the factory with no provision to remove it in the field (the warranty was voided when the cover was removed!). This meter was discontinued in 1903 due to a patent lawsuit brought by Westinghouse.
Photo by Bud Russell

Type C (DC)                                           

(1904 to 1905)
After being barred from making induction meters until the end of 1910 (following a patent lawsuit brought by Westinghouse) in 1903, Robert Lanphier sought out a design for a meter that didn't infringe on Tesla's patents (held by Westinghouse). He decided to work with the mercury-motor meter which was widely used in England at the time, and developed the first practical mercury-motor watthour meter. The design of this meter was unique, since this meter used the voltage coil to generate the braking field instead of the permanent magnets normally used for the brake. The coarse full-load adjustment was made by adjusting the resistance of a shunt inside the meter, and the fine adjustment was made by adjusting the depth of the contacts into the mercury chamber. The light load adjustment was made by varying the resistance of the voltage circuit. Unlike the later mercury-motor meters, this model depended on the disk's natural buoyancy in mercury alone. The rotation of the element was indicated by a hand on the top of the shaft assembly and was visible through a window set in top of the meter cover (which was factory-sealed just like the previous Gutmann Type B meter). This design had several major flaws, the fatal one being that the material used for the mercury chamber softened when the temperature of the surroundings got too warm and leaked. All the Type C meters were recalled and replaced with an improved version (the first version of the Type D).
Photo: Electrical Measuring Instruments and Meters

Types D, D-3 and D-4 (DC)

(1905 to 1913)
The early Type D mercury-motor meter used a new material (Bakelite) for the mercury chambers and the armature disk had a small copper float soldered to it to keep the disk off the bottom of the chamber. Also, the mercury chamber was designed with a pocket that would capture the mercury in the chamber if the meter ever got inverted, to prevent the mercury leaking out of the chamber. There was only one major flaw with this version and that was the mercury ate through the solder holding the float in place, making the armature sink and stopping the meter. In 1907, a new version of the D came out, and had some minor changes in the design, including a cork float which replaced the older copper floats. The D-3 and D-4 were produced only briefly, and no data exists on these other than they were transitional models between the later D and D-5 meters.

Types D (AC Version) & E (Single Phase)

(1905 to 1907)
After Sangamo was barred from making induction-type meters until Tesla's patents expired in 1910, they put a lot of effort in developing watthour meters using the mercury-motor principle (ampere-hour meters using this principle were very popular in England at the time). Shortly after the Type D DC mercury-motor meter was introduced, Sangamo made an attempt to get back into the market for alternating-current meters by adapting this model for alternating current by adding a capacitor in series with the voltage coil. It worked but the accuracy varied widely with small variations of frequency and this version was soon discontinued. In 1906, another attempt was made at an AC mercury-motor meter by using a small voltage transformer instead of the capacitor, and this version was a little more successful. The Type E was a further refinement of the Type D (AC version) and quickly gave way to the new Type F meter.

Type D-5 (DC)

(1913 to 1960s?)
This is the final version of Sangamo's mercury-motor watthour meter. There were no major changes from the earlier models, just numerous small changes that result from trial and error and constant fine-tuning. In addition to the standard 2-wire model, the 3-wire version of the D-5 was first made in a vertical tandem model, but was later made in a horizontal version which contained 2 2-wire D-5s with a common register and differential gearing. Most of the D-5 meters were made up to the 1930s, but continued to be available on a special-order basis into the 1960s.
Photo: Handbook for Electrical Metermen

Types D-5 & F (Switchboard)

D-5 (1913 to 1960s), F (1907 to 1911)
The D-5 DC meter was available in a round back-connected switchboard case and available in 2-wire (shown) or 3-wire versions. All of these were used with external shunts. The large hand is the fastest-moving dial and is used where daily readings are taken. As with the service type, this model saw most of its production up to the 1930s but continued to be available on special order into the 1960s. The Type F switchboard meter was the back-connected version of the Type F AC mercury-motor meter. Like its house-type counterpart, this meter could be used on circuits of all commercial frequencies of its time (25Hz to 133Hz) without requiring different versions for low or high frequencies.
Photo: Electrical Meterman's Handbook

Type F (Single Phase)

(1907 to 1911)
The Type F was essentially unchanged from the previous AC mercury-motor models except the copper disk had a number of radial slots punched in it to reduce the effect of eddy currents induced by the current coil. The internal voltage transformer was used to supply the current that was fed through the mercury chamber. This model would have been dropped as soon as the Tesla patents expired at the end of 1910, clearing the way for Sangamo to sell induction-type meters again.
Photo: David Turner collection

Type H (Single Phase)

(1911 to 1914)
This model had been in development for some time before its introduction in early 1911 but Sangamo had to wait until the Tesla patents invoked by Westinghouse expired in late 1910. At the time, it was the smallest model on the market until the Westinghouse Type OB took that honor for keeps in 1924. This version can be told from the more common later version two ways: First, the base has three mounting flanges and the terminal cover has a raised border with the serial number right along the edge. At first, this model did not have a complete lag coil due to a patent that was still in effect, but as soon as the patent expired, Sangamo sent out literature describing how to connect the coil and calibrate the meter at 50% power factor.
Photo: Electrical Meterman's Handbook

Type H (Polyphase)

(1912 to 1915)
The original version of the H polyphase was simply two H single phase meters in one case. The details of the elements are exactly identical to the single phase version. Unlike the Type H2 polyphase meter, this model does not have a plate with Sangamo's logo on it.
Photo: Electrical Meterman's Handbook

Type H2 (Single Phase)

(1914 to 1928)
By 1914, a few bugs in the original version of the Type H became obvious so Sangamo came out with an improved version of this model. Although the meter is still marked Type H, documentation refers to this meter as the Type H2 to differentiate it from the original version. The changes included moving the lower mounting holes inside the terminal chamber for a more secure mounting (resulting in a larger terminal chamber), replacing the original rubber terminal bushings with sturdier molded bushings, and the light load was changed from a sliding vane to a screw-type adjuster for more precise adjustment. Like all the earlier models produced by Sangamo, the disk on both versions rotates to the left.
Photo: Austin (TX) Energy collection

Type H2 (Polyphase)

(1915 to 1928)
After the H single phase meter got redesigned, the same changes got incorporated into the H2 polyphase meter. Besides the vertical side-connected pattern, there was a horizontal pattern using 2 single phase elements and a differentially-geared register. Using a chart on this meter and the timing of the two disks, the circuit's power factor could be calculated.
Photo: Handbook for Electrical Metermen

Type H2 (Switchboard)

(1914 to 1928)
This model was just the service type in a switchboard case, and was available in round, oval, or rectangular patterns.
Photo: Dean Thatcher collection

Type HC (Single Phase)

(1928 to 1935)
In 1928, the Type H meter was redesigned slightly to incorporate improvements to allow the meter to retain accuracy over a wider range of temperatures and loads. Also, the stator was changed to make the disk turn to the right as with all the other models on the market. Like the previous Type H meter, the HC meters came with either a metal or a glass cover, and later HC meters have a studless cover that attaches to the base with a pair of bayonets.
Photo: David Dahle collection

Type HC (Polyphase)

(1928 to 1934)
With the redesign of the H2 meter into the HC meter, the vertical polyphase models were redesigned to move the terminal blocks to the bottom as the other companies were doing with their polyphase models. A horizontal version was also made, resembling the previous H2 horizontal polyphase meter. A 3-element version of the vertical model was also made and to accommodate the heavier rotor assembly, a spring-loaded jewel bearing was used. 
Photo: Don Price collection

Type HCP (Prepayment)

(1928 to 1934)
This is the earliest prepayment model known made by Sangamo. The case of this meter is of cast aluminum, and the meter element is the same as used in the HC single phase meter. Like some other prepayment meters, this meter took quarters, and by substituting the appropriate gear, this meter could charge between 3 and 15 cents per kwh. The upper three dials indicated the amount of money inserted, the middle dial showed the number of kwh purchased but unused, and the last set of dials is a special kilowatthour register, the gear of what would be the fastest dial (blank on US version, test dial on Canadian version) driving the prepayment counter. When the coin was inserted, the knob was turned until a bell rang, and a switch would complete the circuit through the meter. When the credit ran out, the switch would be opened, breaking the circuit and leaving the customer in the dark until he could come up with more quarters.
Photo: Joe Maurath Jr. collection 

Type HC (Switchboard)

(1928 to 1934)
As with the previous Type H2 model, the HC was available in three different patterns (round, oval, and rectangular). 
Photo: Sangamo Meter Handbook

Types HFS & HFA (Single Phase)

(1934 to 1940)
With the standardization of meters in 1934, the HC element was incorporated into the newly standardized housings. In addition to socket (HFS) and A-base (HFA) versions, two other versions were produced: the HFB and HFC. The HFB had a special 2-part terminal block that allowed testing of the meter in place, and the HFC has the HFB terminal block in an enclosure for outside mounting of the meter. Of the latter versions, GE was the only other company to make similar models: the I-20B and I-20C.
Photo: David Dahle collection 

Type HF (Polyphase)

(1934 to 1937)
With the redesign of the HC into the HF, a polyphase version followed, and as before, the polyphase model is simply two single phase elements in a tall case. 
Photo: Joe Maurath Jr. collection

Type HFP (prepayment)

(1934 to 1940)
The HFP prepayment meter was the successor to the HCP and naturally incorporated the same metering element as used in the HFS and HFA single phase meters. Otherwise, the construction and operation is similar to the HCP (the HFP has a bigger coin box). The meter on the left is the US version, and the one on the right is the Canadian version.
Photo: David Dahle collection 

Type L (Polyphase)

(1937 to 1941)
In 1937, as part of continuing standardization of polyphase meters, Sangamo introduced its L line of 2- and 3-stator polyphase meters. As with Duncan's MG and GE's V line of meters, these meters used a single disk to reduce the meter's size to where they could be produced in a new socket-type version in addition to the bottom-connected (A-base) style. To reduce interference between stators, the L2 had slots near the edge of the solid disk while the L3's disk was laminated. The L3 was a milestone in metering history as it was the first successful 3-stator polyphase meter to use a single disk. As was common with other meters with steel brake magnets, the L's magnet was mounted on a shoe that could be adjusted in and out unlike the previous Sangamo polyphase models that used a fixed magnet. As with the HF single phase, the local ID tag holder was eventually moved from the register to the nameplate (early L meters have a nameplate that looks like a D on its side). 
Photo: David Dahle collection 

Types JS & JA (Single Phase)

(1940 to 1954)
In 1940, the HFS and HFA meter were replaced by the JS and JA meters. The basic concepts behind the HFS and HFA meters were retained and updated. Initially, these meters were to be produced with chrome steel magnets, but just prior to production, these magnet assemblies were replaced with new Alnico magnets. The steel base on the HFS (which was prone to rusting out) was replaced with an aluminum base on the JS.
Photo: Pete Mallet collection

Type LC (Polyphase)

(1941 to 1957)
As the industry abandoned steel brake magnets in favor of sturdier Alnico magnets, the L was redesigned into the LC line of meters. Along with the new magnets, the LC featured a redesigned register and reduced full-load speed for more accuracy. 
Photo: Sangamo Meter Handbook

Types J2S & J2A (Single Phase)

(1954 to 1960)
In 1954, Sangamo came out with the J2S and J2A single phase meters which brought the maximum capacity from 60 amperes in the JS and JA to 100 or 200 amperes in the J2S and 100 amperes in the J2A. Shortly after its introduction, several major changes were made to the J2 meter. The internal frame was changed from cast iron to aluminum and the base on the Class 100 self-contained meters was changed from metal to fiberglass resin. The Class 200 extended-range and the Class 10 transformer-rated versions continued to be produced with a metal-base.
Photo by Austin International 

P Series (Polyphase)

(1957 to 1960)
The P series of meters was simply a further evolution of the LC series. The full-load speed was reduced again for more accuracy, overload capacity of the meter was increased, and the internal frame was redesigned to make the parts more accessible for repair. 
Photo: Sangamo Meter Handbook

Types J2F & PxF (Switchboard)

J2F (1954 to 1960), PxF (1957 to 1960)
The J2F meter was a transformer-rated version of the J2 single phase meter in a semi-flush switchboard-mount case. As with the J2F, the PxF was also the switchboard version of the Px series of polyphase meters (no picture yet).
Photo: Electrical Metermen's Handbook