Frequency Divider with minimum output pulse width


Thread Starter

Neil Waelder

I am trying to locate an "Off the shelf" frequency divider to convert relatively high (100 Hz) pulses to say 10 Hz (i.e. divide by 10). The
input signal is the pulse output (open collector at 24V) from a flowmeter. The output from the frequency divider needs to be 120VAC for use as an input to a PLC.

I have located a number of devices which will divide the frequency, however the divided output is either a very narrow (30 micro sec) or a ratio of the incoming pulse train. (If freq. in = 100Hz and the dive ratio = 10, then the output pulse width is 100Hz x 1/10 = 10Hz. This second method is suitable, but it would be nice to be able to
adjust the output pulse width.

Any suggestions?

Thanks in advance, Neil Waelder, Electrical Engineer, Bomac Inc,

Steve Bailey

Since your goal is to get the frequency signal into a PLC, why not use a High Speed Counter module in the PLC and forget about the frequency divider. Most of the micro PLCs can be configured for up to 5 KHz pulse train inputs. The modular PLCs generally have High Speed Counters that can handle up to 50 KHz.

Kenneth Schunk

If a counter card is too expensive, how about an external counter. I don't have a Red Lion catalog here, but I know that they make small counters that can do what you are looking for. The thing to watch for with an adjustable pulse output is making sure the time is short enough at higher input frequencies that it turns off before it needs to turn on again.

If you have an analog available you could convert the pulse train to analog. Phoenix Contact makes units to do this. Part# 2808255 (Voltage output) or 2808242 (current output) can handle ranges from 0..1KHz to 0..100KHz. You can get information on those modules at: