We have a pulse to current converter which will accept pulse inputs from a proximity speed sensor. I have two queries:

1. The number of teeth on the wheel are known and we also know the maximum RPM the motor will go. We need to put a frequency setting on the Pulse to current converter, how to calculate values for the same?

2. Can any one also tell me how to calculate the value of frequency in the above case when we use the pulse to current converter for flow measurement in turbine flow meter?

 

Firstly to find the required setting for your converter.
Start by converting the motor RPM to RPS (revolutions per second), this makes the calculation easier as the setting for your converter is likely to be in pulses per second or indeed frequency (Hz).

For example for a 1500RPM (25RPS)motor, with say a 10 tooth sprocket would mean that your proximity switch would pulse 250 times per second i.e. 250Hz.

The second item would be specific to the flow sensor used, consideration would also need to be given to the substance being measured. Typically here there may be some scaling required to produce a meaningfull measurement. You could alternatively test the output of the flow device using a frequency meter or oscilloscope. If all else fails there is always trial and error, you will know from the output of your converter if you have selected approximately the right input range.

Hope this helps some!

 

Dear Mihir,

For query no. 1
(No. of teeth x RPM of motor)/60 = frequency in Hz

Set the span of your transmitter corresponding to frequency at maximum RPM and zero corresponding to minimum RPM

For query No.2
Calibration certificates for turbine meters will have a value called K factor. It represents the pulses/m3(unit volume) of liquid. If say you have a turbine meter which can measure 0-1000 m3/hr flow rate and has a K factor of say 2500, then you will see a frequency of 694.4 (2500*1000/3600) Hz at maximum flow rate. Now just plug in the values in your case and you can get the frequency.

Set the span of your transmitter corresponding to frequency at maximum flow rate and zero corresponding to minimum flow rate.

With regards,

Tomy Zacharia

 

Frequency = Pulses per second = HZ
If your wheel has ten teeth and maximum RPM = 1000
then
10 teeth x 1000 RPM = 10000 pulses per minute
10000 / 60 = 166,66 pulses per second = Frequency

Evandro Vizicato
[email protected]

 

freq(in Hz)= num_of_teeth x RPM/60.