Metrohm, 7A501C, safety insulation tester, Ohmmeter No.18A/1 500, GPO
Metrohm, 7A501C, safety insulation tester, Ohmmeter No.18A/1 500, GPO On offer today we have a pristine example of this enigmatic historical meter . This example appears to be GPO issued and we have been quite amazed rot find that it is still available today at a new RRP of over £900!!!!!!!!
Fortunately this example is significantly cheaper. We have fitted a new battery and tested the battery response and reading with a 150 Ohm resistor and the instrument appears to read accurately. A nice item indeed and we add below some manufacturers details on this meter:-
The Metrohm 7A501C safety insulation tester, originally designed for use in hazardous areas – such as mines and petrol sites. With the introduction of the new ATEX regulations, the item no longer meets requirements for intrinsically safe products, however this product has been in active service for 45 years in hazardous areas.
There are no other testers of this kind on the market, that we know of, which fully meet ATEX requirements, therefore the use of this tester should be decided upon by a suitably qualified and knowledgeable person. Whilst this tester does not qualify for ATEX approval, safety officers should evaluate the risks of failing to perform adequate electrical safety testing. Below are the details of the availability and compliance statements issued after the changeover from Intrinsically Safe to ATEX regulations. As such this product is only available for sale where the intended use is outside the EU.
The 7A501C is supplied with test leads, carry case, battery and safety tool to remove battery cover.
Metrohm 7A501C Compliance Statement – July 2003
In 1965, The Factories Inspectorate in the U.K. issued to Edgcumbe Instruments Intrinsically Safe Certificate number 2148, for the Metrohm 7A501C. This approved the instrument as suitable for use as an insulation tester in gases and vapours classified as 2a and 2c in Table I of BS 1259:1958.
“Intrinsically Safe” was permitted to be applied to the instrument, as defined in BS 1259:1958.
In the last 38 years there have been no accidents reported attributable to the use of a 7A501C in explosive atmospheres.
Martindale Electric Co Ltd acquired the product and all associated rights in 2003.
In order to preserve the relevance of the certification, Martindale Electric adheres to the same parts listings and construction techniques as those used by Edgcumbe in manufacture of the 7A501C.
Copies of I.S. Certificate 2148 are available upon customer request.
It should be noted that B.S.1259 was superseded by B.S.5501-9:1982 and more recently by both BS EN 50014:1998 and BS EN 50020:2002.
In addition, the ATEX 94 Directive now applies in certain countries to equipment used in explosive atmospheres and places a different interpretation on the term “Intrinsically Safe”.
The 7A501C will not comply with the ATEX 94 Directive and is marked to this effect.
We now supply the 7A501C as a Safety Insulation Tester.
Ongoing use of existing 7A501C testers in explosive atmospheres is permitted up to July 2006, but new purchases should be ATEX 94 compliant, if they are to be used where ATEX 94 applies.
To our knowledge, there is no ATEX 94 compliant insulation tester available.
In an environment where ATEX 94 applies, the purchase of a new 7A501C to carry out essential electrical safety tests should be subject to a risk analysis by the site safety officer.
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