Pulse Generator

中文

Used for testing and calibrating dose rate instruments such as survey meters or calibrators. STM32G0, KiCad.

This device was built because I purchased a LUDLUM Model 3 and a Model 2360, both of which require calibration of multiple threshold levels, so I made this small tool for that purpose.

Functions:

• 1. Generates adjustable pulses with amplitude 2 mV–1000 mV, pulse width 50 nS–500 µS, adjustable frequency, and selectable positive/negative polarity, for calibration or performance verification;
• 2. Multiple operating modes;
• 3. Output interface changed to MHV connector (previous low-quality BNC connectors could suffer dielectric breakdown);
• 4. Supports USB power supply and battery power; when USB is connected, the battery is automatically disconnected;

Buttons

Button function description

• A: Increment button. When a digit is selected, pressing it increases the value by +1;
• B: Select / Mode button. Short press switches the selected digit position; long press switches the mode (see Modes);
• C: Decrement button. When a digit is selected, pressing it decreases the value by −1;
• D: Pulse Width button. Short press to set, long press to change the multiplier. Range: 500 µS–50 nS, minimum step 50 nS, 4 significant digits;
• E: Frequency button. Short press to set, long press to change the multiplier. Range: 5 MHz–0.1 Hz, 3 or 4 significant digits;
• F: Voltage button. Short press to set, long press to switch between output pulse voltage and input high-voltage value;
• G: Output button. Press to start outputting the configured pulses;

Other operations

• A + B: Switch output pulse polarity to positive polarity pulses (display shows POS_┌┐_)
• C + B: Switch output pulse polarity to negative polarity pulses (display shows NEG‾└┘‾)

High-voltage calibration
How to enter: during power-on, hold F + B to enter calibration mode.

Single-point calibration by default. You can press D / E / F to switch the number of calibration points to 1 / 3 / 5 (updated in V1.2).
During calibration, adjust the displayed voltage to match the input voltage. Keep the voltage unchanged, then long-press the Output button (G) to save the calibration point.
After the required number of calibration points is saved, calibration ends automatically. If the result displays DONE, calibration is successful. If FAILED RETRY is displayed, calibration has failed.

Possible reasons for calibration failure:

• The voltage difference between calibration points is less than 100 V (for example, point 1 is 100 V and point 2 is 150 V);
• No input voltage during calibration;
• The input voltage is not correlated with the displayed voltage;

Modes

Three modes are supported:

• Normal mode (NORMAL MODE): the configured parameters output continuous pulses. During output, a rapidly blinking indicator appears at the lower-right corner of the display to show status;
• Repeat burst mode (REPEAT BURST): the configured parameters are output at 100 CPS;
• Single burst mode (SINGEL BURST): with the configured parameters, each press of the Output button generates exactly 100 pulses;

Schematic

Schematic

Hardware