EF99

I hooked up a camcorder to film the instrument panel (tach, digital speedo, analog speedo) and did a 0-60 run. <O</O
Then I stepped through the video frame by frame (30 fps video).
<O</O
On the way from 0-60 the digital speedometer only shows the following speeds:
2, 11, 18, 27, 34, 40, 45, 50, 56, 60

and it turns out the digital speedometer updates somewhere in the range of every .5-.6 seconds. The analog speedo seemed to be about 6 or 7 frames behind the digital speedo (.2 to .23 seconds).

So my 0-60 time was 4.90 seconds by the digital speedo, and 5.13 seconds by the analog speedo. Hopefully the digital speedo is more accurate.

Anyone else notice their analog speedo lags the digital?

bland

The digital speedo only updates every 500ms or so because otherwise it would just look like a big blur. That means that any time you look at it it could be up to half a second behind the real vehicle speed. The analog indicator is actually also digital. It gets speed data at the same rate as the digital indicator (I don't know whether they are separate units or the same but they are on the same bus) and then needs to move the mechanical needle to that position, which takes time.

EF99

The screen update rate for the digital MPH is just a choice they made for (as you said) making it readable. I don't think the rate that gets displayed is lagged by more than a few milliseconds from the actual measured speed. Defintiely not 500 mS.

bland

Sorry, that's not what I meant to imply. I meant that if it only updates the display every half a second, then in that first millisecond it's timely but that display is aging for up to 500 milliseconds before being accurate again. So when you look down and see a number, it's somewhere between 0 and 500ms old.

This doesn't mean much in normal driving, but if you're doing the kind of measurements that require that level of precision, definitely don't rely on the gauges.