Model 3-IS-1

Intrinsically Safe Gamma Ratemeter

Part Number: 48-3651

Features

• Intrinsically Safe Gamma Survey Meter
• Rugged
• 4-Range Analog Ratemeter
• Built-in Energy Compensated GM Detector
• 0.1 mR/hr to 1.0 R/hr Detector Range

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.

• Specifications
• Options
• Documents
• Low Battery Notes

• Specifications
• Options
• Documents
• Low Battery Notes

Specifications

Application	Gamma surveying in potentially explosive environments
Detector	Internally housed energy compensated GM detector
Detection Range	0.1 mR/hr to 1.0 R/hr
Linearity	Reading within 10% of true value with detector connected
Typical Sensitivity (137Cs)	100 cpm per mR/hr
Meter Dial	0 to 10 mR/hr, BAT TEST
Meter	6.4 cm (2.5 in.) arc, 1 mA analog type
Controls	Rotary Selector: Switches between: Instrument off, Battery check, Ranges: ×0.1, ×1, ×10, ×100 Response Switch: Toggles between FAST (4 s) or SLOW (22 s) from 10% to 90% of final reading Reset Push Button: Zero meter Audio Switch: Audio on/off, Built-in unimorph speaker, greater than 60 dB at 0.6 m (2 ft) Calibration Controls: Accessible from front of instrument (protective cover provided)
Temperature Range	-20 to 40 °C (-4 to 104 °F)
Environmental Rating	NEMA 3R, constructed for either indoor or outdoor use to provide a degree of protection against dirt, rain, sleet, or snow
Relative Humidity	Maximum 95% (non-condensing)
Power	Two each “D” cell batteries (see Warning note below). Batteries are housed in an externally accessible sealed compartment.
Battery Life	Typically greater than 2000 hours with alkaline batteries (battery condition can be checked on meter)
Construction	Cast and drawn aluminum with beige powder coat
Size (H x W x L)	16.5 x 8.9 x 21.6 cm (6.5 x 3.5 x 8.5 in.) including handle
Weight	1.6 kg (3.5 lb), including batteries
Intrinsically Safe Certification	Class I, Division 1, Groups A, B, C, and D, T6 UL 61010-1 & CAN/CSA-22.2 No. 61010-1: Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use - Part 1: General Requirements UL 913: Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous (Classified) Locations CAN/CSA-22.2 No. 157-92 (R2002): Intrinsically Safe and Non-Incendive Equipment for Use in Hazardous Locations

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.

---

Options

Option	Description	Part Number
Transport & Storage Case - Small	Rugged, dust- and waterproof transport and storage case.	2311062
Plastic Disk Check Sources	General purpose check sources used to check instrument response.	Depends on source material and activity.

---

Documents

• Data Sheet
• Product Manual
• Intrinsically Safe Certificate

---

Low Battery Notes

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).

---