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Old 06 November 2012, 16:08   #1
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Analog vs Digital Gauge Accuracy

I was wondering how come my analog tacho differs quite a lot to my Merc System Monitor.

With the Merc Analog Tacho set at 5,000 the System Monitor shows around 4800. Was surprised to see a good 200rpm diff, sometimes even 250 perhaps.

Is this normal?
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Old 06 November 2012, 16:22   #2
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Not sure why they would show a difference but i would go by the system monitor as its taken from the ecu which should be much more accurate.
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Old 07 November 2012, 08:41   #3
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Is it a constant offeset?

Analog tach should be counting the same pulses as the ECU, if it's a constant offset then your analog gauge is not sitting right relative to it's scale on the panel behind the needle. (Mine has a "cal" adjuster on the back, but not all do)


Note both gauges' readings at idle & 500 RPM intervals up to WOT & post back the results.
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Old 08 November 2012, 02:32   #4
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Thanks will compare the two at idle etc and see if there is something I can adjust.
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