Agree an HD50S will do all you need if you just need to detect. There good units but the Quantum XQ models that superseded the HD offered better features, eye display shut off, silent calibration, 2 second startup, colour palettes and sharper/less grainy 17 micron display.
If on a tighter budget I would go for a Quantum Lite XQ30V , theres so much choice at the minute with newer models.