Model 9DP-1*

Ambient Dose Ion Chamber

Part Number: 48-4358

The Model 9DP-1* is a digital, hand-held pressurized ion chamber that provides highly sensitive ambient dose equivalent measurements of gamma and x-ray radiation at energies above 25 keV and beta radiation at energies above 1 MeV. Ambient dose equivalent is defined as the dose equivalent readout that would be measured at a (human) tissue depth of 10 mm. The Model 9DP-1* measures and displays the ambient dose equivalent in accordance with the ICRU (International Commission on Radiation Units) 30 cm tissue equivalent sphere. This requires a special ion chamber that can provide a conversion of the (air kerma) exposure rate to provide the ambient dose and dose rate.

This meter is also specially designed to measure pulsed radiation fields, correctly integrating 50 ns pulses (and wider) that other systems typically miss or measure inaccurately. Another feature is a detector chamber that is only pressurized to 2.5 atm (22 psig), eliminating (USA) shipping and handling HAZMAT concerns. However, this reduced pressure also decreases sensitivity, reducing the minimum measurement point to 2 µSv/h (200 µR/hr).

Measurements and instrument status are displayed on a large 232K-color, backlit LCD screen. The screen displays the current dose rate as well as simultaneously displaying either the integrated dose rate or the peak dose rate in Sv, R, Gy, or rem units. An additional mode, Pulsed Mode, locks the instrument in the highest measurement range in order to improve pulsed radiation response while sacrificing low radiation reading resolution.

The instrument is operated using the four push-buttons below the screen (ON/OFF, FUNCTION, AUDIO, ACK/RESET). In addition to the visual display, click audio proportional to the current dose rate audibly indicates the dose rate level. Two alarm levels can be set to alert the user whenever the pre-programmed level has been exceeded. Alarms are indicated on the display and by an audio tone. The instrument can also be configured for data logging. Logged data can either be stored in CSV format and written to a standard USB drive inserted in the instrument’s USB port, or written directly to a Microsoft Excel spreadsheet by connecting the instrument to a computer running Ludlum’s Model 9DP Logging Spreadsheet Software (see Options).

The Model 9DP parameter settings can be edited by connecting the instrument to a basic USB keyboard. Instrument setup and calibration can also be configured using the Ludlum Dimension Interface Kit, which includes the Dimension Configuration Manager Software and the required USB cable (see Options).


  • Provides ICRU-Based Ambient Dose Measurements
  • Range: 2 µSv/h to 500 mSv/h (200 µR/hr to 50 R/hr)
  • Special Design for Measuring Pulsed Fields
  • Low Pressure Chamber is Non-Hazmat
  • Shows Dose Rate & Either Integrated Dose or Peak Dose Rate
  • Ambient Equivalent Dose or Dose Rate Is Flat Within 30% from 60 keV to 1.3 MeV
  • Sunlight Readable Color Display
  • Auto-Zeroing & -Ranging
  • Rechargeable Batteries
  • Audio & Visual Alarms
  • Data Logging
  • USB Connectivity
  • Free Firmware Updates Through Website




Radiation DetectedGamma & X-rays above 25 keV
Beta above 1 MeV
Correctly integrates pulsed fields with 50 ns pulse widths
Energy ResponseAmbient equivalent dose or dose rate, flat within 30% from 60 keV to 1.3 MeV (see Graph)
Detection Range
  • Sv/h units: 2 – 50 μSv/h, 2 – 500 μSv/h, 0 – 5 mSv/h, 0 – 50 mSv/h, 0 – 500 mSv/h
  • R/h units *:  0.2 – 5 mR/h, 0.2 – 50 mR/h, 0 – 500 mR/h, 0 – 5 R/h, 0 – 50 R/h
  • Gy/h units: 2 – 50 μGy/h, 2 – 500 μGy/h, 0 – 5 mGy/h, 0 – 50 mGy/h, 0 – 500 mGy/h
  • rem/h units: 0.2 – 5 mrem/h, 0.2 – 50 mrem/h, 0 – 500 mrem/h, 0 – 5 rem/h, 0 – 50 rem/h
* Users wanting to take measurements in R/hr units should see the Ludlum Model 9DP-1 which is specifically designed to measure exposure.
Measurement ReadoutsSimultaneous display of rate and either the integrated value, highest (peak) rate, or pulsed mode status
DriftLess than 0.3 μSv/h (30 μR/hr, 0.3 µGy/h, 30 μrem/h)
Chamber Volume220 cc (13.4 in3) volume pressurized to 2.5 atm (22 psig)
Chamber Densitychamber wall density is 601.7 mg/cm2, can wall density is 332.5 mg/cm2. Total density of chamber + can is 934.2 mg/cm2
Accuracy± 10%
Response TimeRanges from 5 seconds in lowest range to under 2 seconds in highest range when measuring from 10% to 90% of final value
DisplayLCD with 8.9 cm (3.5 in.) diagonal; 240 H x 320 W pixels; TFT active matrix; 232K colors; 220 cd/m2; automatic sensor-controlled backlighting
User Controls4 push buttons:
  • ON/OFF
  • FUNCTION (for peak rate, integrate, or pulsed modes)
  • AUDIO (on/off, volume)
  • ACK/RESET (for alarm acknowledgement, meter reset, and clearing integrated dose or peak rate)
Automatic FunctionsAuto-ranging, Auto-zeroing, Auto LCD backlighting
AlarmsTwo levels of radiation alarms available, each is user programmable throughout entire readout range.
Data LoggingData is stored to detachable USB drive in CSV format for easy retrieval by PC spreadsheet/database programs. Data points include date and time, rate, integrated reading, and instrument status. Logging time intervals are set by PC interface program or USB keyboard. (see Options).
Audio OutputsBuilt-in unimorph speaker, > 60 dB at 0.6 meters (2 ft.).
Optional audio jack available for connection to an external headset. (see Options)
USB InterfaceSingle USB 2.0 port. May be connected to:
  • A USB keyboard (with no additional USB ports, and no integrated mouse or trackpad or audio controls) to facilitate password-protected parameter changes
  • A USB memory storage device for storing logged data
  • A PC with the optional Dimension Interface Kit for parameter editing and calibration (see Options)
Warm Up Time< 1 minute when the instrument is in temperature equilibrium with the surrounding environment
Temperature Range-20 to 40 °C (-4 to 104 °F)
Humidity0 – 95%, non-condensing
GeotropismLess than 1%
PowerEight rechargeable “AA” NiMH batteries, supplied with wall charger for direct connection to instrument
Battery LifeApproximately 12 to 30 hours between charges depending on backlighting and USB usage
ConstructionDurable molded plastic with internal metal support
Size (H x W x L)21.9 x 11.6 x 24.5 cm (8.6 x 4.6 x 9.6 in.)
Weight1.5 kg (3.3 lb), including batteries

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