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Encoder Counts and Line Speed Calculator
Calculate quadrature counts, roller travel resolution, line speed, encoder channel frequency and decoded count rate.
Worked example
A 1,000 PPR encoder with x4 decoding and a 1:1 shaft ratio produces 4,000 counts per roller revolution. A 100 mm roller travels about 0.07854 mm per count. At 60 roller RPM, line speed is 18.85 m/min.
- Counts per roller revolution
- 4,000
- Travel resolution (mm/count)
- 0.07853982
- Line speed (m/min)
- 18.84955592
- Encoder A-channel frequency (Hz)
- 1,000
- Decoded count rate (counts/s)
- 4,000
Counts/revolution = PPR × decoding × shaft ratio. Travel/count = π × diameter ÷ counts/revolution. Check whether the encoder specification already states decoded counts, and compare channel frequency and count rate with the exact counter module limits. Slip, backlash and diameter variation are not modeled.
Worked reference · September 17, 2026
PPR, decoded counts and line speed: what changes?
In this calculator, PPR means electrical cycles on one encoder channel per encoder revolution. The counter's x1, x2 or x4 decoding determines how many counts it produces from those signals. Check the manufacturer's definition: a value labeled CPR may already include decoding. Multiplying an already decoded value by four makes the predicted travel per count four times too small.
One roller, three decoding settings
Use 1,000 PPR, one encoder revolution per roller revolution, a 100 mm roller diameter and 60 roller RPM. Circumference is π × 100 = 314.159 mm. Line speed is 314.159 × 60 ÷ 1,000 = 18.850 m/min in all three cases.
| Decoding | Counts / roller rev | mm / count | Decoded counts / s |
|---|---|---|---|
| x1 | 1,000 | 0.31416 | 1,000 |
| x2 | 2,000 | 0.15708 | 2,000 |
| x4 | 4,000 | 0.07854 | 4,000 |
A-channel frequency stays at 1,000 Hz here. At x4, the counter processes 4,000 counts/s. Compare each value with the matching limit in the counter documentation; channel frequency and decoded count rate are different quantities.
Define the shaft ratio explicitly
The ratio input is encoder revolutions divided by roller revolutions. If the encoder turns twice for one roller turn, enter 2. With the same 1,000 PPR and x4 decoding, that gives 8,000 counts per roller revolution and 0.03927 mm/count. At 60 roller RPM, A-channel frequency becomes 2,000 Hz and decoded count rate becomes 8,000 counts/s. Roller line speed stays 18.850 m/min.
Resolution is not positioning accuracy
Smaller travel per count does not remove wheel slip, backlash, diameter error or missed input transitions. Use the effective rolling diameter and verify measured travel under the approved machine test procedure. A numerical result alone cannot qualify a motion or safety system.
Check these before using the result
- Whether the nameplate resolution means cycles per channel or already decoded counts.
- The configured decoding mode and encoder-to-roller ratio, including which shaft carries the encoder.
- Input electrical compatibility, filter settings, maximum channel frequency and supported count rate.
- Actual travel and direction against an independent reference using the site's safe test procedure.
Manufacturer references
- AutomationDirect encoder guide: quadrature signals and decoding
- Encoder Products Company: measuring-wheel resolution
- Encoder Products Company: resolution, RPM and frequency
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Reference: NI encoder measurements and decoding. Review inputs and results against the exact device and site requirements.