I Use Radalert100 Geiger Counter

This counter is nice and is made in the USA, is pretty sensitive and comes calibrated, I did pay about $480 for it and it is one of the best ones out there. Here are key features -

The Radalert 100 is a general purpose geiger counter that measures alpha, beta, gamma, and x-radiation. Exciting new features of the Radalert 100 — as an upgraded version of the popular Radalert 50 — include a three-second update and a utility menu that allows you to change the default settings for several operating parameters. Its digital liquid crystal display (LCD) shows the current radiation level in your choice of milliroentgens per hour from .001 to 110 or counts per minute (cpm) from 0 to 350,000. When SI units are selected, the LCD shows readings in microsieverts per hour from .01 to 1100 or counts per second (cps) from 0 to 3,500. This instrument also offers an accumulated total and timer function, up to 9,999,000 counts and 40 hours. A red LED blinks and a beeper chirps with each count (the chirp can be muted). An audible alert sounds when the radiation reaches a user-adjustable level. The Radalert 100 meets CE certification requirements for Europe.

Specifications:

Sensor:
• Halogen-quenched Geiger-Meuller detector (LND712)
• Mica end window density is 1.5-2.0 mg/cm²
• Side wall is 0.012″ #446 stainless steel
• Detects Alpha, Beta, Gamma, and X-radiation

Display: 4-digit liquid crystal display with mode indicators

Calibration: Cesium 137 (gamma)

Sensitivity: 1000 cpm/mR/hr referenced to Cs-137

Accuracy: ±10% typical; ±15% max. (mR/hr & mSv/hr modes)

Alert: User-adjustable alert level to 50 mR/hr & 160,000 CPM

Count light: Red LED flashes with each count

Audio: Beeper chirps for each count (can be muted)

Ports:
• Output: Stereo 3.5 mm jack sends counts to computers, data loggers, other CMOS-compatible devices, and headphones
• Input: Mono 2.5 mm jack provides electronic calibration input

Power: One 9-volt alkaline battery; average battery life is 2160 hours at normal background, 625 hours at 1 mR/hr with beeper off

Size: 150 x 80 x 30 mm (5.9″ x 3.2″ x 1.2″)

Weight: 225 grams (8 oz) including battery

Options: Computer cable and software (IBM PC compatible)

CE Certified

http://www.medcom.com/rad100.htm