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Maximum demand ammeters

Kelly Marie Angel

I've seen a few fotos recently on  vintage mains plugs  and other curiositys  page on Facebook of the inside of various 11/0,4 kv  substations  they all seem to have ammeters to measure the current on each phase these are max demand meters how do they reset the maximum value indicator? Also do they have a way to record  these values? The meters I've seen all look old  as the hills so not sure what recording technology  was around years ago. I know  these days a lot if these subs have a radio link  at least here in SSE land

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    The old school way was a conventional ammeter movement with a pointer that showed the demand in real time, and a second pointer, often red in colour, that was pushed around the scale by the ordinary pointer. The red pointer therefore displayed the highest reading registered.

    Sometimes a thermal ammeter was used with a time constant of a minute or two, as this avoided recording peaks due to motor starting etc.

    Re-setting was manual by a push button or small knob turned by the fingers.

    The readings were recorded in a record book, either every reading, or only unusual readings.

    The modern is a digital instrument with electronic memory, probably  downloaded to a PC.

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    The old school way was a conventional ammeter movement with a pointer that showed the demand in real time, and a second pointer, often red in colour, that was pushed around the scale by the ordinary pointer. The red pointer therefore displayed the highest reading registered.

    Sometimes a thermal ammeter was used with a time constant of a minute or two, as this avoided recording peaks due to motor starting etc.

    Re-setting was manual by a push button or small knob turned by the fingers.

    The readings were recorded in a record book, either every reading, or only unusual readings.

    The modern is a digital instrument with electronic memory, probably  downloaded to a PC.

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