Fluke Biomedical 451B Ion Chamber Survey Meter

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Fluke 451B
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Manual 451B Datasheet
The Fluke Biomedical 451B 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 has auto-ranging and measure radiation rate and accumulated dose from various radiation sources (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 digital readout, low battery, and freeze (peak hold) mode indicators, 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 (requires sound card) and visual alarm indication.
Fluke 451B Features
  • High sensitivity measurement of rate and dose simultaneously, with the capability to record peak rate
  • 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 and audible alarm
  • Easily-accessible battery door (operated by 2 9-volt alkaline batteries) on the outside of the bottom case
  • Available with dose equivalent energy response (SI units)
Fluke 451B Specs
Radiation detected: Alpha above 7.5 MeV, Beta above 100 keV, and Gamma above 7 keV
Operating ranges: 0 to 5 mR/h or 0 to 50 μSv/h
0 to 50 mR/h or 0 to 500 μSv/h
0 to 500 mR/h or 0 to 5 mSv/h
0 to 5 R/h or 0 to 50 mSv/h
0 to 50 R/h or 0 to 500 mSv/h
Accuracy: Within 10% of reading between 10% and 100% of full scale indication on any range, exclusive of energy response. Calibration source is 137Cs
Chamber: 349 cc volume air ionization
Chamber wall: 246 mg/cm2 thick phenolic
Chamber window: 6.6 mg/cmMylar, protected by steel mesh, 46 cm2 detection are
Beta slide: 440 mg/cm2
451B-DE-SI: In order to achieve energy response consistent with measurements of H*(10) as required by ICR4-47, 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 451B can measure skin dose at 10* (0.07), and Deep Dose H* (10) with Beta shield closed.
Controls ON/OFF and MODE
Automatic features Auto-zeroing, auto-ranging, and auto-back
Warm-up time: One minute
Integrate mode: Operates continuously 30 seconds after the instrument 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