rpm from encoder

Could any body explain how to get speed information from an encoder ? I have incremental encoder of 4096 PPR and 24bit counter. The rated speed is 1500.

Thanks a lot.
 
H

Hinse, Pierre (Sudbury)

Hi there,
just measure the time between pulse and take reciprocal.
or: 4096 / (time per pulse)

With a High Speed Counter card, you can set it up to do pulse width
measurements.

Pierre
 
D

Dom Santilli

Hi there,
If You are working with AB : your count address is "I:1.1" and your speed "I:1.2"

DOM
 
S

shantanu apte

A lot depends upon the type of COUNTER and your exact need .

1) Are you using a COUNTER function provided by PLC / Multi Axes Controller or is it a standalone counter ?

2) Is it a Linear Counter OR RING counter ?

3) Do you want to REMEMBER the position once the POWER is recycled ?

If requirment is not complex then just RESET the counter to ZERO just at the beginning of the counting process and mark this point as HOME . Assum that CW rotation increments the values in +ve direction and CCW in -ve direction .

Set the SCAN time and measure the number of pulses accumulated in that time . Then you can calculate the RPM .

You will need to take care of ripples in RPM as lot depends upon the scan time as well as number of start / stops in a given time period as acc & dec will come in picture .

Shantanu
 
V

Vikas Meshram

Hi Kumar
Your question is very vague, Kindly explain in datail about the counter
and the rest of the electronics. Then only I can help you.
Vikas


**************************************************************************
Vikas W. Meshram
Scientific Officer,
Laser Instrumentation,
Center For Advanced Technology,
Indore- 452 013, MP,INDIA.
Email:[email protected]
**************************************************************************
 
M

Michael Griffin

I believe that both period (the first method) and frequency (the
second method) can both yield equally accurate results. However, each works
best under different circumstances.
Period works best when you have relatively few pulses per update
period (slow speed and/or few pulses per rev) but a time base with high
resolution. Frequency works best when you have a high number of pulses per
updated period (high speed and/or many pulses per rev) relative to your time
base. I once had an application where we had to use both methods (period and
frequency) to cover all speed ranges adequately.
In either case, error is introduced from three sources. Both the
position and the time have a resolution uncertainty of one count at any
instant. Secondly, the time base may run slow or fast. Finally, the encoder
will have some inaccuracy in the angular distance between each pulse mark
(although this should not be very significant with a good encoder).
Some important information which was missing from the original
message was the required speed calculation update time, and the time base
accuracy, resolution, and maximum value before overflow.
Once these are known, it is straight forward to do some sample
calculations (keeping in mind timer and counter overflow) to see which will
work best. Sometimes the details of how the hardware works (e.g., the timers
and counters) impose additional constraints.


**********************
Michael Griffin
London, Ont. Canada
**********************
 
S

shantanu apte

A lot depends upon the type of COUNTER and your exact need .

1) Are you using a COUNTER function provided by PLC / Multi Axes
Controller or is it a standalone counter ?

2) Is it a Linear Counter OR RING counter ?

3) Do you want to REMEMBER the position once the POWER is recycled ?

If requirment is not complex then just RESET the counter to ZERO just at
the beginning of the counting process and mark this point as HOME . Assum
that CW rotation increments the values in +ve direction and CCW in -ve
direction .

Set the SCAN time and measure the number of pulses accumulated in that
time . Then you can calculate the RPM .

You will need to take care of ripples in RPM as lot depends upon the scan
time as well as number of start / stops in a given time period as acc &
dec will come in picture .

Shantanu
 
You can get voltage (+-10V) info from encoder.
Try to see SGs Thompson aplication note AN242.
IC L290 converts pulses to voltage
 
L

Leonid Gannel

Generally for transition from encoder to analog taxo the quadrature (A, B) encoder signals must be converted to other format – two channels: Direction CW and Direction CCW. Those are two sequences of *4 evaluated pulses for both directions of rotation. After that you need only in two frequency-to-voltage converters (or low pass filters for simplicity) for each one and different amp for addition.
Feel free to contact me for details.
[email protected]
 
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