Atec Fluke-451B User Manual

451B

Ion Chamber Survey Meter with Beta Slide

The 451B state-of-the-art ion chamber survey
meter is a handheld battery operated unit
designed for use in both rugged and normal
environments. The 451B includes a sliding beta
shield to serve as an equilibrium thickness
for photon measurements and enables beta
discrimination. The 451B auto-ranges and
measures radiation rate and accumulated dose
from various radiation sources (alpha, beta, x-ray,
gamma). The ion chamber detector allows for
a fast response time to radiation from leakage,
scatter beams, and pinholes. Additionally, the
low-noise chamber bias supply provides for fast
background-settling time.

The digital display features an analog bar
graph, 2.5 digit readout, low battery indicator,
freeze (peak hold) mode indicator, and an auto­matic backlight function. User controls consist of
an ON/OFF button and a MODE button. The case is
constructed of lightweight, high strength materials
and is sealed against moisture.

The RS-232 interface can be connected directly
to a computer for use with the Excel add-in for
Windows (451EXL), enhancing the functionality
of the instrument. This software allows for data
retrieval, user parameter selection and provides a
virtual instrument display with audible and visual
alarm indication.

Technical Data

Key features

• Measures skin dose (slide open) and deep dose (slide closed)

• High sensitivity measurement of rate and dose simultaneously

• Records peak rate using “Freeze Mode”

• Auto-ranging and auto-zeroing

• RS-232 communications interface with optional Windows-based Excel add-in for

data logging

• Ergonomic, anti-fatigue handle with replaceable grip, wrist strap and tripod mount

• Programmable flashing LCD display

• Easily-accessible battery door (operated by two 9-volt alkaline batteries) on the

outside of the bottom case

• Available with dose equivalent energy response (SI units)

Specifications

Radiation detected Alpha > 7.5 MeV

Beta > 100 keV
Gamma > 7 keV

Operating ranges,
response time

Accuracy Within 10 % of readings between 10 % and 100 % of full scale indication on any range,

Detector Chamber (cc volume air

Automatic features Auto-zeroing, auto-ranging, and auto-backlight
Warm-up time One minute
Display LCD analog/

digital with backlight

Modes Integrate mode Operates continuously 30 seconds after the instrument

Environmental Temperature range -20 °C to 70 °C (-4 °F to 158 °F)

Typical energy
dependence

Power requirements Two 9 V alkaline, 200 hours operation
Dimensions (WxDxH) 10 cm x 20 cm x 15 cm (4 in x 8 in x 6 in)
Weight 1.11 kg (2.5 lb)

0 mR/h to 5 mR/h (8 sec)
0 mR/h to 50 mR/h (2.5 sec)
0 mR/h to 500 mR/h (2 sec)
0 R/h to 5 R/h (2 sec)
0 R/h to 50 R/h (2 sec)

exclusive of energy response

349 cc

ionization)
Chamber wall (phenolic) 246 mg/cm
Chamber window (mylar) 6.6 mg/cm
Beta slide 440 mg/cm

2

2

2

Analog 100 element bar graph 6.4 cm long. Bar graph is divided

into 5 major segments, each labeled with the appropriate
value for the range of the instrument

Digital 2.5 digit display is followed by a significant zero digit

depending on the operating range of the instrument. The
units of measurement are indicated on the display at all
times. Digits are 6.4 mm (0.25 in) high. Low battery and
freeze indicators are also provided on the display

has been turned on. Integration is performed even if the
instrument is displaying in mR/h or R/h

Freeze mode Will place a tick mark on the bar graph display to hold on

the peak displayed value. The unit will continue to read
and display current radiation values

Relative humidity 0 % to 100 % (at 140 °F)
Geotropism < 1 %

16

Nitrogen gamma rays are 110 % to 120 % of indicated readings as determined at the

University of Lowell

2 Fluke Biomedical 451B Ion Chamber Survey Meter with Beta Slide