Fluke Biomedical 451B - Manual (Page 24)

451B
Operators Manual
14
The microprocessor performs data collection, averaging, and multiplication by
stored calibration factors, range changing, and battery check functions, in
addition to driving the LCD. Between computational periods, it “sleeps” in a low
power mode to conserve battery power. The microprocessor reads stored
information from an electrically erasable memory, EEPROM, which is used by
the program for calibration and display units. The EEPROM will retain stored
data when the Survey Meter is OFF or when the batteries are removed. Data can
be entered into the EEPROM using the RS-232 port.
63 V collection voltage for the ion chamber is obtained from lithium cells that
have a 10 year life. All internal power for the Survey Meter is supplied by the 9 V
batteries, accessible from the rear of the Survey Meter.
The digital and bar graph displays read directly. The bar graph display update
periods are listed in Table 2. The digital display updates at 1 second intervals
nearest the current bar display update. The bar graph and digits display do not
always show the same reading because the bar graph is faster than the digital
update. It is more convenient to watch the bar graph when the reading is
changing quickly and to read the value of a slowly changing or static reading by
looking at the digital display.
The bar graph display is a digital presentation, programmed to appear as a linear
analog meter display. It is also referred to as the analog display throughout this
manual.
Table 2. Bar Graph Display Update Periods
Range Update Period
50 R/h (500 mSv/h) 0.05 second
5 R/h (50 mSv/h) 0.1 second
500 mR/h (5 mSv/h) 0.1 second
50 mR/h (500 µSv/h) 0.15 second
5 mR/h (50 µSv/h) 0.25 second