# Mark-Space Ratio

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1. Mar 22, 2016

### nathan27th

Hi if I had the ratio of 4:1 and the frequency of 10Khz how would I go about finding the time?

2. Mar 22, 2016

### Staff: Mentor

Who which what?

3. Mar 22, 2016

### Jeff Rosenbury

Perhaps you could cut back on other activities? It's always hard to find time, but if something is important most people manage.

Another term for the mark space ratio is duty cycle.

At 10kHz, the entire wave is 100µs and the active part (usually the high part) is 4/5th of that, so 80µs.

To get this I divided 1 cycle by 10,000 cycles per second and got 1/10,000 (100µs) of a second. Since the mark space ratio divides the cycle into parts, I divided the active parts of the ratio (4) by all the parts of the ratio (4+1=5) and got 0.8. I then multiplied 100µs times 0.8 and got 80µs.

4. Mar 23, 2016

### Baluncore

Frequency = 10 kHz. Therefore period, T = 1 / 10k = 100 usec.

Ratio 4:1 could mean ( 4 marks + 1 space ) = 20%
That would give mark time = 4/5 * 100 usec = 80 usec and the space time = 20 usec.

The “ratio of 4:1” is a bit confusable. It might mean 20%, 25%, 75% or 80%.
A “ratio” suggests a simple division, not a relative proportion such as 4:1 = 4 / (4 + 1 ).