Port-Powered Frequency Counter

The 232FC lets you make frequency measurements of TTL level signals with any RS-232 port. It is powered from the port handshake lines. If the lines are not available, a 12 VDC external supply can be used. Frequency measurements can be made from 5Hz to 2MHz with less than ±2% error at 2 MHz. Duty cycle measurements can be made from 5 Hz to 50 KHz with an error of ±6.5% at 50 KHz. Simple commands let you take measurements with your own program. Included software will log and plot frequency and duty cycle information plus display histograms. There is also sample code in BASIC, Pascal, and C that demonstrates the 232FC commands.