Ludlum Model 3-90 Survey Meter

Radiation Safety Officer

Specifications

Indicated Use	– Alpha, beta, gamma survey
Detector	– Internal pancake style G-M detector with 1.7 ± 0.3 mg/cm² window
Area	– Active : 15.4 cm² – Open : 12.2 cm²
Efficiency (2π geometry)	– ¹⁴C : 10% – ⁹⁰Sr / ⁹⁰Y : 45% – ⁹⁹Tc : 38% – ³²P : 65% – ²³⁹Pu : 30%
Sensitivity	– Typically 3300 cpm/mR/hr (¹³⁷Cs gamma)
Audio	– Built in unimorph speaker with ON/OFF switch (greater than 60dB at 2 feet)
Meter Dial	– 0 - 5 cpm, BAT TEST (others available)
Multipliers	– X0.1, X1, X10, X100
Linearity	– Reading within ±10% of true value
Calibration Controls	– Accessible from front of instrument (protective cover provided)
Response	– Toggle switch for FAST (4 seconds) or SLOW (22 seconds) from 10% to 90% of final reading
Reset	– Pushbutton to zero meter
Power	– 2 each "D" cell batteries (housed in sealed compartment that is externally accessible)
Battery Life	– Typically 600 hours with alkaline batteries
Battery Dependance	– Less than 3% change in readings to battery endpoint