rpm counter

hello everybody
i try to mesure the rpm from a diesel engine with a proxyswitch connected to the 5khz counter from a siemens 95u plc.
i have activatet the counter in DB1
i have 60pulses per rev and 1500rev/min=25rev/sec so 25x60=1500puls/sec then i call the counter in OB13(100ms)
then the counter has to count 100ms (150 pulses)and then has to reset and start over.
L PW 36
L PW 37
T MW 1
KZ 0
T PW 36
T PW 37
then i wanted to multiply the MW1 with 10 to get the rev/min.
but this is not working
has somebody a idea how i get this solved?

Hi,
Be sure your prox-sw. is enough fast for thouse impulses/time-unit. If not use some pulse-encoder.
Please put f.e ..CAP 60000 .. to DB1.
Program must re-start after DB1 editing.
If counter count over 60000, program OB3 executes if
programmed..

OB3 is for counter overflow...

A E 35.0 

R E 35.0

L kf+60000

T PW 36





OB13

L PW 36      LOAD COUNTED INPUT

T MW  1      SAVE COUNTER

L KF+60000   SET  COUNTER BY

T PW 36      COUNTER OUTPUT

Dead right Seppo, the prox needs to be very quick. Usually a mag pickup is used for this but the output is only about 5 volts.
Check that the prox is fast enough, the pulse width from the prox is long enough for the PLC to pick it up. Basically, the pulse needs to be at least twice the length of the PLC scan time.
Look at using a high speed conter card or run the prox/mag pickup into a transducer with 4-20ma output and then into an analogue card.
DO NOT USE THE PLC FOR OVERSPEED. Use a dedicated device or you may be looking at a pile of bits.

Multiply in S5-95U must do with standard FB242 in the CPU, but you can do it otherwise as follow:

OB13

L PW 36      LOAD COUNTED INPUT

SLW 1        MULTIPLY BY 2 (ACCU1) shift left 1-bit

L PW 36      ACCU1 GOES TO ACCU2

SLW 3        MULTIPLY BY 8 (ACCU1) shift left 3-bits

+F           ACCU1+ACCU2

T MW  1      MULTIPLYED BY 10 !!!!



L KF+60000   SET  COUNTER BY

T PW 36      COUNTER OUTPUT

hello
the proxyswitch i use is working till 3khz so that must be enough.
i only do not know iff the puls is long enough but i just try it i think it is 50/50 on/of.
60pulsesx33rev/sec=1980hz.
1sec:1980=0,5ms for 1 puls=0,25ms on and 0,25ms off i think it is a little bit short!
i go try to write the program this weekend now i have seen it i also understand it
thanks for the good and quick response
thanks again robert