# Conversion to 8.68us units

#### Wetmelon

Hi all,

I'm running a microcontroller that has me program times in 8.68microsecond units, and I'm having an issue converting 10ms to 8.68us units, then counting a number (scalar) then taking that number and getting RPMs from it.

Here's what I have so far:

10ms = 10,000us

10,000us/8.68 ~ 1152 (8.68us units) --> Is this right?

The program counts a number of pulses for 10ms, and returns that value, for example, in 10ms at 6,000 RPM I should see

6,000RPM = 100R/s (Hz) = 1R/10ms = 1 pulse

Then I want to convert from the one pulse back up to RPMs, so I need a scalar, I guess 6000 would be correct across all RPMs?

I feel like I've made a mistake here somewhere, but have I done this correctly?

#### Mark44

Mentor
A bit late, but in case someone else has a similar question:
10,000us/8.68 ~ 1152 (8.68us units) --> Is this right?
To the nearest unit, yes.
6,000RPM = 100R/s (Hz) = 1R/10ms = 1 pulse
That works for me.
Wetmelon said:
Then I want to convert from the one pulse back up to RPMs, so I need a scalar, I guess 6000 would be correct across all RPMs?
Yes, if I understand what you mean. There's a linear relationship between the number of pulses and the RPM, according to this formula: $R(n_p) = 6000n_P$. If there is one pulse ($n_p = 1$), then R = 6000 (rev. per min). If there are two pulses, R = 12,000.

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