comp probe circuit

Posted on Feb 5, 2014

This circuit is a stable frequency counter accurate to 5 significant digits. The range is 0 - 30MHz with an input sensitivity of greater then 100mV. The probe connects to the PC serial port. So by using the crystal oscillator already present on your PC serial card and software calibration, the Probes` external circuitry is kept to a minimum. Probe

comp probe circuit
Click here to download the full size of the above Circuit.

9 can also be used as a logic probe/analyzer using included software (LPROBE92. EXE). The software to use this probe can be downloaded using the following link. Note that this software is compiled for Intel x86 platforms and runs under DOS, Win95, Win98 and WinMe. It does not run under any Windows version based on NT including Windows NT 3. 51, WinNT4, Win2K, Win2K3, WinXP and Windows Vista. This is because NT based operating systems do not allow direct hardware access. SETPROBE. EXE is the frequency counter calibration program. To give accurate readings the Probe must be calibrated to your PC. SETPROBE. EXE calculates the constant error correction factor for the particular PC serial card the probe is to be used on. The frequency counter corrects for this slight constant error in crystal frequency by using the correction factor contained in PROBE. DAT. To calculate this correction factor, a reliable oscillator of known frequency (eg 2MHz Crystal Oscillator) is required. When CALIBRAT. EXE is run, the Probe will sample the frequency and then ask for the true frequency value in HZ. The frequency entered must be to 1 Hz accuracy (no decimal points) or an error will occur (for example "200123" not "200123. 34" or "2003. 421 kHz"). The program then calculates constant error correction factor and stores it to PROBE. DAT. Calibration is only necessary once. LPROBE92. EXE is the logic analysis program. Logic states are displayed...

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