Fluke 481 Ion Chamber Survey Meter Operators Manual
The Fluke 481 Ion Chamber Survey Meter is a handheld, battery-operated device designed to measure beta radiation above 100 keV and gamma/x-ray radiation above 7 keV. It features an auto-ranging and auto-zeroing display with a 2 1/2-digit LCD and analog bar graph. The unit includes an audio alarm, backlight, and freeze mode for peak value tracking. It operates on two 9V batteries and has a phenolic shield for beta and photon measurements. Maintenance includes battery and window replacement, desiccant regeneration, and recalibration procedures.
The manual provides detailed instructions for operation, installation, troubleshooting, and maintenance, including specifications for radiation detection ranges, response times, and precision. It also includes contact information for Fluke support and calibration services.
| Radiation Detected | Beta above 100 keV, gamma above 7 keV |
|---|---|
| Operating Ranges | 481: 0 to 5 mR/h, 0 to 50 mR/h, 0 to 500 mR/h, 0 to 5 R/h, 0 to 50 R/h |
| Precision | +10 % of reading between 10 % and 100 % of full-scale indication on any range, exclusive of energy response |
| Detector | 349 cc volume air ionization chamber; phenolic chamber wall 246 mg/cm2. Chamber window is composed of 6.6 mg/cm2 Mylar. A coating of graphite has been applied to the walls to make them conductive. The collection potential is -63 Volts. The Chamber is vented through the desiccant |
| Response Time | Less than one minute for initial operation. Time measured from 10 % to 90 % of final value for a step increase/decrease in radiation rate such that a range change does not occur. |
If the instantaneous radiation rate exceeds 50 R/h (0.5 Sv/h), the 'R' in R/h or the 'Sv' in Sv/h will blink to notify the user.
Two 9V batteries provide over 200 hours of continuous operation.
The precision is ±10% of the reading between 10% and 100% of full-scale indication on any range, exclusive of energy response.
The initial operation time is less than one minute, and the time to reach 10% to 90% of final value for a step change in radiation rate is 8 seconds for the 0 to 5 mR/h range, 2.5 seconds for the 0 to 50 mR/h range, and 2 seconds for higher ranges.