Integrate Mode; Freeze Mode; Auto-On Backlight; Specifications - Fluke 481 Operator's Manual

Integrate Mode

The Integrate Mode allows the Model 481 to display the integrated exposure. Exposures
are accumulated up to 999 R (9.99 Sv).

Freeze Mode

The Freeze Mode will move a "bar" on the bar graph display to show the user the peak
value, and will lock on the maximum range. The unit will continue to read and display
current readings.

Auto-On Backlight

The Model 481 is equipped with a backlight which automatically turns on when ambient
light drops below a predetermined level. The backlight will turn off when the ambient
light exceeds the predetermined level, which is factory set.

Specifications

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
Accuracy................................................................ ±10 % of reading between 10 % and 100 % of full-scale indication on
Detector ................................................................. 349 cc volume air ionization chamber; phenolic chamber wall
Warm-Up Time....................................................... Less than one minute for initial operation
Response Time ..................................................... Time measured from 10 % to 90 % of final value for a step
Precision................................................................ Within 10 % of reading
Readout.................................................................. Liquid Crystal Display: Contains an analog bar graph with a permanent
External Controls .................................................. ON/OFF button, MODE button.
Automatic Features .............................................. Ranging and zeroing are fully automatic.
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481-DE-SI: 0 to 50 Sv/h, 0 to 500 Sv/h, 0 to 5 mSv/h, 0 to 50 mSv/h,
0 to 500 mSv/h
any range, exclusive of energy response (Calibration source is 137Cs)
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
481-DE-SI: In order to achieve energy response consistent with
measurements of H*(10) as required by ICRU report 47, aluminum has
been added to the back wall, 38 % of the side wall area, and to the
beta slide. With the Beta Shield open, the 481 can measure skin dose
at H* (0.07), and Deep Dose H* (10) with the Beta shield closed.
increase/decrease in radiation rate such that a range change does not
occur:
481: 0 to 5 mR/h, range: 8 seconds. 0 to 50 mR/h, range: 2.5 seconds.
0 to 500 mR/h range: 2 seconds. 0 to 5 R/h, range: 2 seconds. 0 to
50 R/h, range: 2 seconds
481-DE-SI: 0 to 50 Sv/h, range: 8 seconds. 0 to 500 Sv/h, range:
2.5 seconds. 0 to 5 mSv/h, range: 2 seconds. 0 to 50 mSv/h, range:
2 seconds. 0 to 500 mSv/h range: 2 seconds
NOTE: Instantaneous exposure rate is limited to 50 R/h (0.5 Sv/h),
including but not limited to a pulsed field.
scale on the display and a 2 1/2 digit display. Analog Display: The bar
graph consists of 100 segments, 2 1/2 inches long; the scale has five
major divisions; the appropriate value for the operating range of the
instrument will appear below the scale. Digital Display: The digital
display is 2 1/2 digits followed by a significant zero digit depending on
the operating range of the instrument. The leading 1/2 digit is blank, or
a "1" or a "0" for clarity. Units of measure appear to the right of the
digital display. Appropriate multipliers also appear on the display units:
As indicated under Range, programmable in R/h or Sv/h
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Specifications
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