[Mgs] Mgs Digest, Vol 195, Issue 1

[Barney Gaylord]

I dunno abott that "formal engineering 
nomenclature" stuff.  I'm an engineer, and in my 
world "rev counter" may be the British (English) 
term for a tachometer, but otherwise rev counter 
and tachometer are the same thing in the 
automotive world, regardless of the type of signal input.

Just for reference, here are examples of dozens 
of tachometers, many mechanically driven and 
having nothing to do with ignition systems or any kind of electrical input:
https://duckduckgo.com/?q=hand+tachometer&iax=images&ia=images&iai=https%3A%2F%2Fwww.cetm.com.sg%2F1534-superlarge_default%2Facision-tm1100-hand-held-tachometer.jpg&t=ffab


At 02:44 AM 8/3/2023, Paul Hunt wrote:
>....
>Both those are describing the function of the 
>instrument which is the same in both cases and 
>is not the point in question. Even so the first 
>definition includes the statement "In formal 
>engineering nomenclature, more precise terms are used to distinguish the two.".
>
>The PO's question was how do I connect a 
>_tachometer_ , and the answer to that is 
>fundamentally different to a rev counter. rev 
>counter displays the rate at which a cable drive 
>is turning, a tachometer measures the time 
>between successive electrical pulses. In the rev 
>counter case it doesn't matter whether it is on 
>a 4, 6 or 8 (etc.) cylinder whereas for a 
>tachometer the pulses from an 8 cylinder engine 
>are coming in at twice the rate of a 4-cylinder 
>and there have to be _internal_ differences in 
>the tachometer to display that correctly. If the 
>terms are used interchangeably then when 
>responding to a (formal engineering?) question 
>you would first have to establish which one is being talked about!
>
>PaulH.


>On 02/08/2023 14:29, dave northrup wrote:
>>
>> From Wikipedia
>>
>>A tachometer (revolution-counter, tach, 
>>rev-counter, RPM gauge) is an instrument 
>>measuring the rotation speed of a 
>><https://en.wikipedia.org/wiki/Axle>shaft or 
>>disk, as in a motor or other 
>>machine.<https://en.wikipedia.org/wiki/Tachometer#cite_note-1>[1] 
>>The device usually displays the 
>><https://en.wikipedia.org/wiki/Revolutions_per_minute>revolutions 
>>per 
>><https://en.wikipedia.org/wiki/Revolutions_per_minute>minute 
>>(RPM) on a calibrated analogue dial, but 
>>digital displays are increasingly common.
>>
>>The word comes from 
>><https://en.wikipedia.org/wiki/Greek_language>Greek 
>>τάχος (t¡chos "speed") and μέτρον 
>>(métron "measure"). Essentially the words 
>>tachometer and 
>><https://en.wikipedia.org/wiki/Speedometer>speedometer 
>>have identical meaning: a device that measures 
>>speed. It is by arbitrary convention that in 
>>the automotive world one is used for engine 
>>revolutions and the other for vehicle speed. In 
>>formal engineering nomenclature, more precise 
>>terms are used to distinguish the two.
>>
>> From dictionary.com
>>
>>tachometer
>>
>>[ ta-kom-i-ter, tuh- ]SHOW IPA
>>
>>----------
>>noun
>>    * any of various instruments for measuring 
>> or indicating velocity or speed, as of a machine, a river, or the blood.
>>    * an instrument measuring revolutions per minute, as of an engine.


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