Model 451P Ion Chamber - Pressurized

Micro Roentgen Survey Meter for Gamma and X-ray

The Fluke Model 451P Ion Chamber is used in a wide range of medical and health physics applications. The Model 451P Ion Chamber was designed to measure leakage and scatter around diagnostic X-ray and radiation therapy suites. Furthermore, the Model 451P is ideal for site surveys and is regularly used by X-ray manufacturers, radiation therapy, government agencies, state inspectors, research labs, biomedical technicians, and in airports for baggage inspection equipment maintenance. This Ion Chamber was manufactured by Victoreen which was owned by Inovsion, Cardinal Health, Syncor, and presently Fluke Biomedical.

Waterproof Pelican Cases Available

For questions or to order, call 310 589 0601 or email:

Model 451P Ion Chamber (Pressurized) SPECIFICATIONS

Radiation Detected: Gamma and X-rays above 25 keV

451P Operating Ranges

0-500 µR/h or 0-5 µSv/h

0-5 mR/h or 0-50 µSv/h

0-50 mR/h or 0-500 µSv/h

0-500 mR/h or 0-5 mSv/h

0-5 R/h or 0-50 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 137 Cs

Detector Chamber: 300 cc volume pressurized air ionization chamber to 6 atmospheres

Controls:ON/OFF and MODE

Automatic Features: Auto-zeroing, auto-ranging, and auto-backlight

451P Response Time: Analog response time from 10% to 90% of reading for a full scale step increase is dependent on operating range. Response time for a step increase in radiation exposure rate from background:

Step increase, Step increase, background to Time to reach 90% of final value (seconds)
400 ÁR/h 4.8
4 mR/h 3.3
10 mR/h 4.3
40 mR/h 4.5
100 mR/h 2.7
1 R/h 2
4 R/h  2.7

The following table shows time measured from 10% to 90% of final value for a step increase or decrease in exposure rate such that a range change does not occur. These values are the response times for the various ranges:

Range 10% - 90% (seconds)
0-500 ÁR/h (5 ÁSv/h) 5
0-5 mR/h (50 ÁSv/h) 2
0-50 mR/h (500 ÁSv/h) 1.8
0-500 mR/h (5 mSv/h) 1.8
0-5 R/h (50 mSv/h) 1.8

Power :Two 9-volt alkaline, 200 hours operation

Display:LCD analog/digital with backlight

Warm-Up Time Less than two minutes for initial operation when the instrument is in equilibrium with ambient temperature


Temperature Range: - 20░C to + 50░C

Relative Humidity:0 to 100%

Geotropism: Negligible

Typical Energy  Dependence: Nitrogen gamma rays are 110% to 120% of indicated readings as determined at the University of Lowell

Dimensions: 4 in (w) x 8 in (d) x 6 in (h) (10 x 20 x 15 cm)

Weight:2 lb 6 oz (1.07 kg)

451P Models and Accesories:

Model 451P-RYR: 451P w/standard ion chamber 

Model 451P-DE-SI-RYR 451P w/Dose Equivalent ion chamber

Options : Model 451EXL Excel add-in for Windows « and RS-232 interface cable

Model 190HPS Single Unit Carrying Case

Model 190HPC Multiple Unit Carrying Case

Model 62-103137 Cs 10 ÁCi Check Source

Modes : Integrate mode perates 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

Waterproof Pelican Cases Available

Direct Scientific  /  tel (310) 589 0601 /   Email

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