Modern Electromechanical Meters (1960s to Present)
Duncan/Landis+Gyr
Duncan (1901-1975) | Landis&Gyr (1975-1998) | Siemens PT&D (1998-2002) | Landis+Gyr (2002-)
Duncan Types MQS & MQA (Single Phase)
(1960 to 1969)
The MKS and MKA were superseded by the MQS and MQA in 1960. The MQ line of meters were identical to the previous MK meters except for two things: The brake magnet was redesigned from a single magnet to a set of three Alnico V and one Alnico VI magnets (the Alnico VI magnet was movable and was used as the full-load adjustment) on the left and right sides of the stator. The other major change was to replace the jewel bearing used in the MK with a magnetic suspension similar to the one incorporated in the GE I-50 meter. The MQA was made in smaller quantities before being dropped because of decreasing demand for single phase A-base meters.
Photo by David Dahle
Duncan MR Series (Polyphase)
(1963 to 1969)
Following the introduction of the magnetic bearings on the MQ single phase meter, the MH (transformer-rated) and ML (self-contained) polyphase meters were redesigned to incorporate magnetic bearings, and all other characteristics of these meters (including the different full-load speeds) were retained. Also, on the transformer-rated versions, the voltage indicators were finally abandoned in favor of the low-wattage bulbs long used by the other manufacturers.
Photo by David Dahle
Duncan Type MR-WF Series (Switchboard)
(1963 to 1969)
We have no data on this line of switchboard meters beyond the model numbers. Our best guess is that they were available in the same surface or semi-flush mount cases as the MH-W line, used the MR meter element (and similar designations), and would have a test switch built in (the 'F' designation?).
Type MS (Single Phase)
(1969 to 1994)
The MS replaced the MQ in 1969 and was a complete redesign for a lower profile and to take advantage of further improvements in meter design. Among other small improvements, the adjustments were rearranged to allow for automatic computer calibration of the meter. Also, the light-load adjuster was changed from the usual movable plate to a coil with an adjustable slug. Also, in keeping with other manufacturers' designs, the register and nameplate were redesigned to present a more solid front. While the self-contained 3-wire version was replaced by the MX in 1994, the K-base and transformer-rated versions of the MS did continue in production for a few more years.
Photo by David Dahle
Duncan MT Series (Polyphase)
(1969 to 1993)
Following the introduction of the MS single phase meter, the MT polyphase meter made its appearance. This line of meters marked a return to the laminated disk last used on the MG line of meters. Although the arrangement of stators was similar to the other manufacturers', the light and lag load adjustments on this line of meters were different. Instead of the usual movable plates, the adjustments were made by moving a slug within coils extending from the stator cores. Also, the type designator was changed from the service type to the form number (MR-3S became MT-16S, MR-2 1/2PT became MT-6A, etc.).
Because of the growing demand for electronic polyphase meters that could collect far more information than their mechanical counterparts, Landis & Gyr discontinued the MT line of meters in favor of their SSM and Sx electronic polyphase models.
Photo by David Dahle
Landis & Gyr Type MX (Single Phase)
(1994 to 2009)
The MX was a complete redesign with the ability to retrofit the meter for various types of third-party AMR devices. One result of the redesign was that the disk was moved up to the vertical center point of the meter to assure plenty of room for the devices. Also, unlike any other modern meter, the disk was relatively thick and lacked corrugations or stippling. The MX was only offered in the self-contained 3-wire version (Form 2S); manufacture of this model was discontinued in June 2009 in favor of the FOCUS electronic single phase meter.
Photo by David Dahle
General Electric (1892-)
Types I-55S & I-55A (Single Phase)
(1954 to 1988)
The I-55 superseded the self-contained I-50 meter, increasing the overload capacity from 60A to 100A, partly from using heavier wire on the current coils and introducing better overload compensation (667% instead of 400%). The I-55 also had better voltage compensation that allowed 240V 3-wire meters to be used on 120V 2-wire services without having to calibrate the meter at 120V first. The majority of the I-55 meters were made through the 1960s, but the I-55A and special versions continued to be available for some time after that.
Photo by David Dahle
Type I-60S (Single Phase)
(1957 to 1972)
The I-60S was the final evolution of the I-50's design. This meter had a full-load rating of 30 amps and using the 667% overload compensation introduced with the I-55 meant this meter could safely handle up to 200 amps, superseding the 50-amp I-50S meter (which used 400% overload compensation). This was accomplished by mounting the voltage and current coil assemblies separately to the frame and which allowed the current coils to move in relation to the frame without affecting the calibration. The earliest I-60S meters had the same solid front as the I-50 and I-55 meters, but with S/N #42,400,000, a post was added to the frame for the nameplate to allow separate mounting of the nameplate and register. Also, I-60 meters up into the 43 million series had butyl rubber sleeving on the current coils, while later I-60 meters have epoxy-coated current coils.
Photo: Schenectady Museum Archives
Type V-60 Series (Polyphase)
(1957 to 1999)
This series of meters was a redesign of the V-series of meters to take full advantage of the new Alnico V magnet (it no longer needed to be moved in and out for the full-load adjustment) and to incorporate the magnetic bearing introduced with the I-50. Also, the base was redesigned to be made entirely of compression-molded material. The models were renumbered by adding a 6 to the type number (V-2-S became V-62S, V-3-A became V-63A, etc.).
Initially only the two-stator versions were offered, but in 1963, the three-stator V-64, V-67, and V-610 (in both socket and A-base) were introduced. Also, another model was introduced for 3-wire network services and was numbered V-61S, V-611S, and finally V-612S as it evolved (a smaller version of this model was also built for a while as Type I-63S which resembled the I-55S meter).
Also, some totalizing meters were later introduced which used 2 meters within one enclosure (with both a magnetic suspension and a float bearing on the shaft). These were the V-63-2A, V-64-2A, and the V-65-2A and these used the old 'bathtub' case for the older 3-stator V-series meter (with a special terminal block having enough terminals for both meters).
In 1999, due to the increasing demand for GE's electronic polyphase models (Phase 3 and the kV), the V-60 line of meters was dropped.
Photo: GE Metering Products catalog
Types DS-50 & DS-60 (Switchboard)
(1957 to 1999)
With the introduction of the V-60 series of meters, the older DS series of meters were superseded by the DS-50 and DS-60 line of switchboard meters. These meters have the same elements as the transformer-rated V-60 polyphase meters and follow the same numbering scheme. The DS-60 series was the standard version with a connecting plug used to complete the connections between the meter cradle and the case (removing the plug activates a built-in bypass for the current connections) and which could easily be exchanged for a test plug. The DS-60 cradle could also be removed from the case for repairs if needed. The DS-50 series was a lower-cost version with the cradle hard-wired to the case (the cradle could be moved forward for testing but an external test switch was required with these meters).
Photo: GE DS-50/60 Meter Manual
Type I-70S (Single Phase)
(1968 to 2006)
The I-70S was a redesign of the I-60S for a lower profile and lighter weight by using a smaller and more efficient voltage coil assembly. The frame was also treated with a corrosion-proof powder coat finish. The earliest I-70S meters have two full-load adjusters, one intended for factory adjustment only. Some of these were initially produced with a shiny finish on the aluminum register and nameplate, and were replaced by the more common dull finish after complaints that they were hard to read on a sunny day. In 1970, the I-70S/1 was introduced which eliminated one set of brake magnets to improve the meter's efficiency and made it more immune to loss of magnet strength from surges. The I-70S/2 meter was introduced in 1973 and has aluminum current coils and surge relief gaps. A lower-cost version of the I-70S was introduced after production was transferred to Mexico (sandblast finish on the inner frame instead of powder coating; base uses less material; current coils made of copper). As part of the industry's transition to electronic meters and acceptance of the new I-210 meter, the I-70S was discontinued.
Incidentally, an A-base version of this meter (type I-70A) was developed and is presently used in Canada.
Photo: Austin International
Sangamo/Itron
Sangamo (1899-1975) | Schlumberger (1975-2004) | Itron (2004-)
Types J3S & J3A (Single Phase)
(1960 to 1970)
The J3 series of meters was a major redesign introducing a magnetic float suspension similar to the one on the Westinghouse D2S. Also, the retarding magnets were now mounted in the frame itself instead of being bolted to a shelf as on the previous J and J2 models, reducing the side thrust on the bearings. As with other manufacturers at the time, the current coils were now coated with epoxy (replacing enamel and fiberboard laminations). The self-contained J3S (both Class 100 and Class 200 versions) had the same white plastic base as the later J2S. The transformer-rated J3S meter was initially produced in a metal-base version but eventually changed over to use the new plastic base. Most of the J3 meters were produced with a 100:1 gear ratio between the disk and register pickup, but a few were produced with a 50:1 ratio (a precursor to the J4?) and were specially marked on the register.
Photo by Austin International
Type J4S (Single Phase)
(1970 to 1984)
The J4S was a complete redesign of the J3S for lighter weight and lower profile. It's been said this was in part due to the beautification campaign led by President Lyndon B. Johnson's wife in the late 1960s. This model is unique in that it uses a tapered cover and had a metal sunshield (it initially was standard but after roars of disapproval, it became a seldom-ordered option). Other changes include a new baseplate made of Bakelite material and separate mounting of voltage and current coils to the frame.
Photo by David Dahle
Type J5S (Single Phase)
(1984 to 2004)
The J5S was a slight redesign of the J4S to adapt it for automated assembly equipment and to improve its performance. The earliest J5S meters are labelled as Sangamo but this was soon changed to incorporate the Schlumberger name and logo. This model was discontinued in favor of the newer and more popular Centron meter.
Photo by David Dahle
P0 Series (Polyphase)
(1960 to 1968)
When Sangamo introduced the J3 single phase meter with magnetic bearing in 1960, the P line of polyphase meters was also reintroduced with a magnetic bearing. To designate the changeover from jewel to magnetic bearings, a zero was added to the model number - i.e., the P2SY became the P20SY etc. In all other respects, the P0 line of meters was identical to the previous P line.
Photo: Sangamo Meter Handbook
S Series (Polyphase)
(1966 to 1986)
The S line of meters was introduced in 1966 and replaced the P series over the next 2 years. It was a complete redesign, the main change involving the frame assembly - it was now a one-piece 'wrap-around' assembly that also included the register mount and brake magnets. The only disadvantage is that complete disassembly of the meter is required to get at the disk. The same methods used previously to prevent interference between stators were carried over to this line of meters - slotted disks on the 2-stator models and laminated disks on the 3-stator models. Also, the S used the same white fiberglass-reinforced base that was introduced with the previous P0 line of meters. The model designators follow the numbering scheme GE used with their V-60 series of meters - i.e., Sangamo's S5S = GE's V-65S, S3A = V-63A etc.
Photo by David Uy
SL Series (polyphase)
(1986 to 1990s)
The SL line was a slight redesign of the S series, and the most noticeable change is the base which was now made of the same material as used on the J5S single phase meter. (more data on the S to SL transition later) The entire SL line has given way to electronic polyphase versions (the Vectron and Sentinel).
Types PF, SF & SLF (Switchboard)
Currently have no information on these types.
Westinghouse/Elster
Westinghouse (1886-1990) | ABB (1990-2002) | Elster (2002-)
Types D2S & D2A (Single Phase)
(1960 to 1963)
The D2S and D2A were mostly identical to the previous DS and DA meters, the biggest difference being the bearing system. The jewel and ball bearing that had been used ever since the Type A was replaced by a new magnetic float bearing (called the "Magnethrust" system). Earlier D2S and D2A meters used the same molded polyester for insulation on the current coils as on the DS and DA meters, but in 1961, this was changed over to butyl rubber which was a far better insulation solution. Also, the cover flange and sealing pin on the DS was replaced with a longer-lasting (and more standard) stainless steel flange that was adapted to the aluminum breakaway "T" seals coming into use at that time.
Photo by David Dahle
Type D3S (Single Phase)
(1963 to 1968)
The D3S meter was a slight improvement over the D2S with improved sealing and gasketing techniques as well as eliminating one set of retarding magnets. The frame was also redesigned to make it easier to test the meter using the light-beam revolution counters coming into use at that time. Earlier D3S meters have the current coils embedded in butyl rubber but this was changed to epoxy coating on the conductors to improve the insulation characteristics.
Photo by David Dahle
Type D4S (Single Phase)
(1968 to 1983)
The D4S meter was a complete redesign of the D3S meter for a lower profile and lighter weight. This was accomplished by using a smaller disk and mounting the voltage and current coil assemblies separately on the frame. Unlike the previous models, the light-load adjustment on the D4S is accessible from the front. Some of the last examples of this model (produced alongside the succeeding D5S meter) did have issues with the disk bearings, causing accuracy concerns on light loads.
Photo by David Dahle
Type D5S (Single Phase)
(1983 to 1996)
As with the earlier version of this model, a regular jewel and pivot bearing was used, except the jewel mounting was rotated by way of a gear train coming off the left-hand register dial. Also, this is the only model made by Stanley Instrument Co. to incorporate a lag adjustment which was functionally similar to the lag coil used on other manufacturers' models. This meter used a round case with two terminal boxes: the lower one contained the current coil connections while the upper one was for the voltage coil tap. Another unique feature of this meter is the cover - it merely slides onto the base and a sealing wire is then used to seal it in place.
Photo by David Dahle
Type AB1 (Single Phase)
(1996 to 2009)
As part of ABB's restructuring of their meter line, the D5S was renumbered the AB1 - otherwise there was no change in this model. After ABB sold its metering division to Elster in 2003, the Elster logo was phased in, and manufacture of this model continued until the end of April 2009. With the industry now embracing electronic single phase meters, manufacture of the AB1 and AB1R (this version has factory-mounted power leads and painted disk for field installation of AMR modules) was discontinued. To meet existing customer demand for electromechanical single phase meters, Elster now offers the AB1G. These are AB1 meters of fairly recent manufacture that were already removed from service and which Elster repurchased and refurbished as new.
Photo by David Dahle
D2 Series (Polyphase)
(1960 to 1968)
The D2 line of polyphase meters was a slight redesign of the DSP / DAP line of polyphase meters. The most important change was to replace the jewel bearing with a new magnetic bearing that required far less maintenance. Also, the polyester insulation previously used was replaced by butyl rubber on the transformer-rated versions and epoxy-coated current coils on the self-contained versions. The two-part frame was retained but the retarding magnet on the rear part of the frame was eliminated.
D4 Series (Polyphase)
(1968 to 1983)
The D4 line of polyphase was a redesign of the D2 line of polyphase meters. The frame was redesigned to make it one piece instead of 2 as well as making it so it could be used on both 2- or 3-stator meters. This was accomplished by mounting the voltage and current coil sections separately to the frame. The disk on the D4 line of meters is larger than the one used on the D2 line of meters (opposite from the single phase D3S to D4S disk design transition).
D5 Series (Polyphase)
(1983 to 1996)
The D5 line of polyphase was mainly a refinement of the D4 line of polyphase meters. More info soon.
ABS Series (Polyphase)
(1996 to 2002), Elster ABS Series (2003 to 2008)
As part of ABB's restructuring of their meter line, the D5 series of polyphase meters was simplified. The D5A series of polyphase A-base meters was dropped due to utilities upgrading A-base installations with socket adapters or replacing with new meter sockets. Also, demand registers were dropped as an option due to strong customer preference for the Alpha meter in demand applications. Lastly, the polycarbonate cover that was optional on the D5 polyphase meters became standard on the ABS meters. This line of models was finally discontinued in 2008 in favor of Elster's line pf Alpha electronic polyphase meters.
Photo by David Uy
Type D2B (Switchboard)
(1963 to 1968)
The D2B line of switchboard meters incorporated the same construction as the D2S singlephase and the D2 line of polyphase meters, and all have the test switch built in for testing the meter in place (just visible in the lower front of the photo).
Photo by Russ Bower
Type D4B (Switchboard)
(1968 to 1983)
The D4B line of switchboard meters incorporated the same type of construction as the D4 line of polyphase meters. The photo shows the internal construction and the test switch in more detail (compare to the D2B photo). The cover for the D4B is similar to the D2B except the lower part of the cover is plain (no corrugations).
Photo by Ed Ranucci
Type D5B (Switchboard)
(1983 to 1996)
The D5B switchboard meters were similar to the previous D4B models and was dropped in 1996 in favor of the Alpha electronic switchboard meter.