Air Ionization Chamber Survey Meter - Model 9-4
Introduction

The Ludlum Model 9-4 is a rugged air ionization chamber for performing beta-gamma dose rate measurements over a five-decade span ranging from 0–500 mSv/h (0–50,000 mR/hr). The ion chamber automatically compensates for changes in temperature and pressure. The chamber wall, including the instrument case, is 1000 mg/cm². A 1000 mg/cm² retractable beta shield allows beta measurement with a 7 mg/cm² window.
 
The six-position selector switch selects Off, x10K, x1K, x100, x10 and x1. Other controls include an On/Off switch for a meter light, reset and battery test buttons, and a zero adjustment knob. An adjustable shoulder strap, included, provides a convenient and comfortable mode to carry the instrument during surveys.
 
The Model 9-4 is equipped with a serial interface for calibration. An optional calibration kit supplies the necessary interface cable, software, calibration can, pressure pump, and serial-to-USB converter.

Alternate Instruments

Model 9-3: Same as Model 9-4 less pressure compensation with audio output and screw driver adjusted calibration