How old is my meter?
What is it?
People regularly contact me asking how old their newly acquired
vintage instrument might be. This often proves very difficult since
Evershed and Vignoles used the same method of construction for their
instruments over many years. I have tried to establish whether it might
be possible to estimate the date of manufacture from the serial
numbers. I have looked at information given to me by contributors and
searched the internet and examined the entries on auction sites. From
what I have been able to glean it would seem that the serial numbers
start from a low number and increase over the years. There does not
appear to be any kind of date code included in the numbers, though it
seems likely that blocks of serial numbers were allocated for
instruments of a particular type. I have two earth testers which
support this: series 1 earth tester
886915 internally marked 5/52 with instruction card 7-50 and a
series
4 earth tester 1954 pattern 816925 with instruction card 4-56
I have so far found 40 instruments and pieces of equipment [not
exclusively meggers] where serial numbers have been given or are
visible on photos. The earliest, an ammeter dated 1895 has a serial
number 1,656 and the latest, a megger has a serial number 2,606,230. By
correlating the numbers with the dates for the various patents etc. I
have produced this very rough guide to those manufactured at
the Acton works from 1903.
9 000 after 1903
48 000 after1910
96 000 after 1919
147 000 after 1926
170 000 after 1928
260 000 after 1935
320 000 after 1940
430 000 after 1942
650 000 after 1946
720 000 after 1946
800 000 after 1950
1 000 000 after 1954
1 100 000 after 1957
1 500 000 after 1963
2 000 000 after 1968
The origins of the firm begin in 1886 and although it lives on under
the MEGGER label it ceased manufacturing at the works at Acton Lane in
1986. The following is a time line history of the firm which I trust
will help date instruments made by the firm prior to the takeover by
AVO International in 1986. It would seem that there were periods when
the firm was making instruments to both the new and the old designs.
They also manufactured instruments based upon a principle patented a
year later.
1881 Professors Ayrton and Perry invent the voltmeter and ammeter [they
also coined the words]
1882 Ayrton invents the first true ohmmeter with moving magnet and two
coils
1885 Evershed makes his first moving iron voltmeter
1886 Evershed working for Goolden and Trotter in Westminster, London
1886 Soft iron armature voltmeters and Cardew hot wire ammeters
switchboard instruments
1888 Weston USA produced the first moving coil instrument
1889 Goolden and Trotter started making a two part ohmmeter with
magneto and separate meter
1889 Ayrton and Perry's ohmmeter and hand generator patented
1890 The single needle design replaced with two magnetised in opposite
directions
1890 New generator design gives smoother output
1888 Manufacture started in Westbourne Park, London
1895 Evershed and Vignoles started at Woodfield Works, Harrow Road,
London
1899 E&V started making moving coil meters
1899 Generator improved again, transformer stampings roller bearings
rotating disc commutator and patented, this design to become the '1900
pattern' testing set
1903 Move to new factory in Acton Lane Chiswick, London
1903 The word MEGGER registered as a trade mark
1903 Meter with moving coils and centrifugal clutch incorporated for
first time
1904 The meter and generator are housed in one box 'Megger testing set'
with or without slipping clutch.
1905 'Bridge megger testing set', insulation, Wheatstone bridge and
cable
fault detection in one box [200MΩ to 0.01Ω]
1909 set up agents in other countries including USA
1909 Murday pen recorder unique rectangular scale
1910 Biddle in USA start making Meggers
1910? DIONIC water conductivity tester 4mA at 100 V
1910 DUCTOR low resistance tester 15A at 1V [typical] power supplied
from battery
1922 lighter model in aluminium
casing 'MEG insulation testing set' 0-100 Mohm introduced later to be
called the series 2 which remained in production until 1963
1922 The inventor of what was to become the AVOmeter approached the
company with a view to manufacture. The offer was rejected by Sydney
Evershed
1926? Earth testers in both the 'megger' and 'meg' range available
1929 'Bridge Meg' introduced [metal casing]
1930 Improvements to meter pole pieces to linearise the scale
1931 'Megger' and 'meg' earth testers
1931 Midworth control system
1932 'WEE' megger introduced [Bakelite case] made in response to a
smaller prototype made by GEC
1941 'WEE' megger updated RC components added
1946 Safety ohmmeter introduced
1947 'Noflote' level control system
1950 The whole range of ohmmeters redesigned to be more sensitive
reclassified as 'Series 1' (0-2000 Mohm)'series 2'(0-100 Mohm and
'series 3'
1950 Series 4 introduced
1951 instruments start appearing with a new logo EVERSHED surrounded by
a parallelogram
1955 E&V acquire Record Electrical Co Ltd a firm started in 1911 by
JW Record
1960 Series 3 Mk 3 with AC generator and diode rectifier introduced,
insulation and continuity tester, nylon gear wheel.
1960 E&V producing 32 instrument variations
1961 E&V taken over by BAT, rationalisation introduced
1961? Instruments start appearing with a new logo MEGGER
surrounded by
a parallelogram
1962 Transistorised continuity and insulation tester introduced. This
used a milliammeter movement rather than the crossed coil movements of
the hand cranked versions
1963 Line earth loop tester introduced for testing of installations for
compliance with IEE wiring regulations
1963 Major Megger replaces the series 2, available in 4 versions
1963 AC generators with diode rectifier or doublers instead of the DC
type used since the 1880s
1965 BAT sold E&V to George Kent
1967? Kent and Cambridge Instruments merge
1967 Thorn take over of Metal industries which owned AVO Ltd
1968 AVO acquires Evershed and Vignoles manufacture continues at Megger
Instruments Division of E&V Ltd (instruments also being made in
Dover)
1971 Parts of E&V disposed of to Metal Industries (part of the
Thorn Group)
1982 Part of Thorn EMI Instruments Ltd together with AVO and HW Sullivan
1983 E&V owned by BestoBell (then Meggitt in 1986) until 1990
1986 Chiswick factory closes
1991 Name change AVO Megger instruments Ltd
2000 Name change AVO international Holdings
2002 Name change AVO International Ltd
2002 Name change Megger Group Ltd
In the early 1950s Evershed & Vignoles had four divisions, 3 at
the Acton Lane works in Chiswick:
Instrument Division
Controls Division
Naval Division
and
FHP Motors Division at the
Devonshire Works, Dukes Avenue, Chiswick
The other companies in the Evershed Group at this time were:
Record Electrical Company Ltd,
Altrincham
[This lives on as Record Electrical
Associates Limited formed in 2003, bringing together Record Electrical and Townson & Mercer.]
Evershed Power-Optics Ltd,
Harlequin Ave, Isleworth
In the late 1960s/early 1970s located at what had been the Taylor boat
building site in Chertsey. They made digital control equipment for
television cameras and related equipment. Radamec (Radar Mechanicals) were
here from1981 to 2003 on the same site. They made optical control
systems for the defence and television markets and marine and
environmental control systems. Rademec acquired by Ultra in 2003
Berg&Burg NV, Amsterdam
Evershed-Enraf, France
Evershed & Vignoles (Canada) Ltd
1956
Thos, Walker & sons Ltd,
Birmingham [naval instruments]
Evershed-Enraf GmbH, Solingen
Germany
Evershed-Enraf, Delft, Holland
Subsequent re-organisations:
Evershed & Vignoles
ElectroDynamics Division at Acton Lane
Evershed & Vignoles Powerrotor Division at Acton Lane then
at Dukes
Avenue
In1990 this division of Evershed and Vignoles was acquired by Moore
Reed which started out in 1962 thus combining two of the UK’s leading
servo component companies under a new flag Control Techniques Dynamics Ltd
(CTD) based in Andover. In 2017 CTD became a subsidiary of the Nidec group the world’s No�1
comprehensive motor manufacturer, handling 'everything
that spins and moves', miniature to gigantic - purchased all of the
'Electric Motors & Drives division' of Emerson.
I would welcome corrections or updates to the above note that the figures given are typical values, instruments were made for a wide range of applications.
Acknowledgments
C M Deavin for copies of original Evershed and Vignoles
documentation provided by Marion Heard, the publicity assistant at
Megger back in 2003.