Pulse Counter — Setup Guide

The NHI Pulse Counter is a browser-based audio pulse counter and PGD-17 companion app.

Quick Start

1. Open app.northharbourinstruments.com/geiger/ on your phone or laptop
2. Tap Start Listening and allow microphone access
3. Place your device near the detector speaker
4. Adjust Sensitivity until pulses are detected reliably

Installing on Your Phone

iPhone / iPad

1. Open the app URL in Safari
2. Tap the Share button (box with arrow)
3. Tap Add to Home Screen
4. The app now works offline like a native app

Android

1. Open the app URL in Chrome
2. Tap the Install banner, or Menu → Add to Home Screen
3. The app now works offline like a native app

Settings

Setting	Description	Default
Sensitivity	Detection threshold — higher = more sensitive	50%
Center Freq	Target beep frequency in kHz	4.266 kHz
Bandpass Width	Width of the frequency filter in Hz	400 Hz

Troubleshooting

Not detecting pulses?

• Increase Sensitivity to 70–80%
• Make sure the microphone is within ~30cm of the speaker
• Check that the Center Freq matches your detector's beep frequency
• On iPhone, ensure Safari has microphone permission: Settings → Safari → Microphone → Allow

Too many false counts?

• Decrease Sensitivity
• Narrow the Bandpass Width to filter out background noise
• Move away from other sound sources

How It Works

The app uses a bandpass filter centered on your detector's beep frequency (default 4.266 kHz), amplifies the filtered signal, then runs an envelope follower at the full sample rate (~48,000 times per second) to detect individual pulses via rising-edge detection.