This intrinsically safe general purpose ratemeter is patterned after Ludlum's best-selling Model 3. It was designed and tested to USA standards for intrinsic safety, permitting it to be used in potentially explosive atmospheres.
This instrument includes an internally housed, energy compensated GM detector with a gamma detection range of 0.1 mR/hr to 1.0 R/hr. The Model 3 type instruments are well known for their accuracy and long-lasting dependability. The cast aluminum instrument housing, with its separate battery compartment and accompanying metal handle, offer an industrial robustness and quality that promote long-lasting protection and instrument life. The front panel controls include a rotary switch for selecting the four-decade range, instrument shut-off, and battery test, an audio on/off switch, a fast/slow response switch, and a count reset button.
WARNING: Use only Duracell Procell PC1300 1.5 V type "D" batteries. To reduce the risk of ignition of a flammable or explosive atmosphere, batteries must be changed only in a location known to be a non-hazardous area.
WARNING: When repairing this unit, substitution of components may impair intrinsic safety.
Use caution when using batteries that are low but are still above the LOW BAT mark with the detector in a high radiation field. When the detector is moved to a relatively high field the current to the detector may be high enough that the low battery steady audio is triggered. This low battery audio overrides the audio on/off switch, so this audio tone will be heard regardless of the position of the audio on/off switch. If the meter is turned to the BAT check position, the user can then see that the battery power level is below the LOW BAT mark. The radiation reading may or may not be correct when the low battery warning is active. There is no permanent harm done to the instrument. Replace the batteries with a fresh set of the approved type per the instrument manual. This problem is caused by the current limiting resistor necessary for the intrinsically safe rating, and the current drawn at relatively high radiation fields (for example: at or above approximately 100 mR/hr with the 44-9 pancake detector).
