IM-4100 Frequency Counter The Heathkit IM-4100 Frequency Counter is a solid-state frequency counter which can accurately measure frequencies to over 30 MHz. The counter is also a period meter and an events counter. SPECIFICATIONS FUNCTIONS Frequency . . . . . . . . . . . . . . . . 5 Hz to 30 MHz Period . . . . . . . . . . . . . . . . . 1 usec resolution to 99.999 sec Totalize . . . . . . . . . . . . . . . . 1 – 99,999 events INTPUT Frequency Range . . . . . . . . . . . . . 5 Hz to 30 MHz minimum Sensitivity . . . . . . . . . . . . . . . 15 mVrms (50 mV, 5 Hz to 50 Hz) Period Pulse Width . . . . . . . . . . . 25 nsec minimum Low Frequency Signal Risetime . . . . . . 1 msec for signals less than 10 Hz Input Impedance . . . . . . . . . . . . . 1 Mohms shunted by less than 35 pF Protection . . . . . . . . . . . . . . . 240 volts rms at 60 Hz Attenuator . . . . . . . . . . . . . . . X1, X10, X100 fixed compensation TIME BASE Setability . . . . . . . . . . . . . . . +/- 1 ppm Frequency . . . . . . . . . . . . . . . . 10 MHz Temperature Stability . . . . . . . . . . +/- 1- ppm, maximum 0o to 40o ambient OSCILLATOR CONNECTION External Input Frequency . . . . . . . . DC to 20 MHz External Input Sensitivity . . . . . . . TTL or 2.5 Vrms from 50 ? source Internal Output . . . . . . . . . . . . TTL signal at 1 MHz GENERAL Gate Interval . . . . . . . . . . . . . kHz – 1 msec, MHz – 1 msec (Indicated by gate light) Manual Gate . . . . . . . . . . . . . . DC control in events mode using external OSC input connector Display Time . . . . . . . . . . . . . . 200 msec plus gate interval Power Requirements . . . . . . . . . . . 105 – 130 or 210 – 260 VAC (switch selected), 50 – 60 Hz, (at 25 watts); or 9 – 14 VDC at 1.25 amperes Dimensions . . . . . . . . . . . . . . . 7-1/4” wide, 10-1/2” deep, 2-3/4” high (less handle) Weight . . . . . . . . . . . . . . . . . 5 lbs