Maintenance; Preventative Maintenance; Routine Cleaning - Fluke 481-DESI Operator's Manual

minor divisions are worth 0.05, 0.5 or 5. The incremental nature of both the digital
reading and the analog bar graph provide greater accuracy for reading in different
portions of the scale. For example, on the 0-5 mR/h (0-50 Sv/h) range, with a digital
reading of 2.0 and above, the analog bar graph can be read more accurately than the
digital display. Below a digital reading of 2.0, the digital display is more accurate
because it consists of three significant digits. The stated precision of the digital display is
accurate only above a reading of 0.20 on the 0-5 mR (0-50 Sv) scale.
The same analysis applies to all the other ranges because the number of
significant digits or active bar elements are independent of the position of
the decimal point or the units multiplier.
There is a small hysteresis built into the range changing circuit so that the instrument
does not keep changing scales if the reading is at the threshold of range change. It is
important in calibration of the instrument that the calibration coefficients track from
range to range because an oscillatory condition can occur if the calibration on a given
range is low and the coefficient for the next more sensitive range is high.
In addition to FREEZE, the other message that can appear on the display is LOW BAT.
When the LOW BAT message appears, the batteries should be changed within one hour.
The display will indicate HI for good chamber voltage bias condition.
The program in the 481 ROM is proprietary to Fluke. The firmware version appears in
the digital part of the LCD display (prior to the "all elements on" display) when the
instrument is turned on. The firmware program consists of three main parts: operation,
communication, and monitoring.
The operation portion of the firmware performs all of the control functions needed to read
and control the electrometer and range change amplifier, calculate radiation rate, and
display the calculated values on the LCD Display. In addition, the measured data are
smoothed and displayed in an exponential manner with time that simulates the rise and
fall time of an ordinary meter display. Range changing is performed automatically. If a
large increase in signal is detected, the range changing skips to higher ranges bypassing
exponential rise with time to get to the new reading quickly. The instrument continually
integrates the detected radiation signal and saves the accumulated amount that may be
read by the operator at any time. The operator may also reset the integration process.

Maintenance

Very little maintenance is required for the survey meter, but some periodic attention may
be necessary, especially if the instrument is used in harsh industrial conditions.

Preventative Maintenance

Very little maintenance is required for the survey meter, but some periodic attention may
be necessary, especially if the instrument is used in harsh industrial conditions. The
desiccant must be renewed and replaced periodically. See the Desiccant Regeneration
section in this manual.
Install fresh batteries prior to performing any calibration on this
instrument.

Routine Cleaning

Do not immerse the Model 481 or 481-DE-SI. The unit is not waterproof; liquid could
damage the circuits. The unit should be kept clean and free from dirt and contamination.
The unit may be cleaned by wiping with a damp cloth using any commercially available
cleaning or decontaminating agent.
Shop for Fluke products online at:
Note
Note
MyFlukeStore
www.
Ion Chamber Survey Meter
1.877.766.5412
.com
Maintenance
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