Direct Reading (Pocket) Dosimeter

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1 Direct Reading (Pocket) Dosimeter What is a Pocket Dosimeter???? Direct Read Pocket Dosimeters are rugged, precision instruments about the size of a pocket fountain pen, which are used to measure accumulative doses or quantities of gamma & X-ray radiation. A metal clip is used to attach the dosimeter to an individual's pocket or to any available object in an area to be monitored for total radiation exposure. It is pocket-size, conductive-fiber electroscope with an ion chamber for detecting and indication integrated exposure to gamma and x-radiation. It has a thin wall which permits the penetration and detection of radiation. If your Dosimeter is going to be used in harsh conditions where scratching of the lens is a concern we recommend a synthetic sapphire window to protect the lens even in the toughest of conditions. Range and Model Information Dosimeter Range Model 0-2 mr mR mR/RM 138 Rate Meter 0-2 msv 138-S mr msv 500-S mr R R R R R R 746 Rate Meter RM The model 138, 138-S,500 and 500-S are available with a protective hard window which prevents the lens from being scratched. Other models can be special ordered with this feature. Reading a Dosimeter How does the Dosimeter work? The way we "read" a dosimeter is to just point it at a light source so that we can look through it and see the scale. The conductive fiber moves across a very clear well marked scale that produces the reading. Direct-Reading dosimeters use an extremely sensitive fiber electrometer type voltmeter and a small volume of air to measure the total amount of radiation to which the instrument has been exposed. A reading may be made at any time by merely looking at a source of light through the eyepiece end of the instrument. The reading here is at zero. This particular dosimeter is the 200 mr model.

2 Direct Reading (Pocket) Dosimeter Specifications: Radiation Detected: Ranges: Energy Response: Detector: Detector Housing: Accuracy: Rate Response: Electrical Leakage: Temperature Range: Gamma and X-ray from 16 KeV to 6 MeV mr to R See Response curve below Fiber electrometer mounted in an electrically conducting plastic ion chamber Very low permeability plastics - hermetically sealed Within + or - 10% of true exposure Dose rate independent for gamma and x-radiation Less than 0.5% of full scale for 24 hours at 50 degrees C -20 degrees C to 50 degrees C Relative Humidity: Up to 90% Dimensions: Length 4.5 in. (12.4cm), Diameter: 0.6in (1.5cm) Weight: 1.0 oz. (25 grams) Finish: Barrell and end caps: Natural matte black Clips: Metal clips Warranty: 2 year limited warranty

3 THE JORDAN CHARGER FOR DIRECT READ DOSIMETERS Jordan Nuclear Charger Model JN (Jordan Nuclear) POWER: 1 ea. "D" Cell battery Range: volts Mil-Spec: NSN BATTERY LIFE: Capable of recharging dosimeters thousands of times. SIZE: 4"(10.2 cm)w X 4"(10.2 cm)l X 3"(7.6 cm)h WEIGHT: 1.2 lb (495 grams) 1 YEAR WARRANTY The is a compact lightweight instrument designed to charge direct reading pocket dosimeters. The Jordan Charger is a compact lightweight charger designed to charge most direct-reading quartz fiber dosimeters. This instrument features a fully transistorized and printed circuit board. Power required for operation is furnished by a single "D" flashlight type battery, capable of recharging dosimeters thousands of times before replacement is necessary, thus making it an economical and reliable charger to operate. A safety spring located in the charging socket of the Model 750-D prevents damage to the dosimeter in the event that excessive pressure is exercised when recharging. Both moistureproof and dust-proof, the charger also features a protective cap to prevent any moisture or dust from accumulating in the charging socket when not in use. The dosimeter has a built-in string electrometer and ion chamber. The Jordan Charger is used to impress a charge on this ion chamber. A zero position on the built-in scale will indicate that the dosimeter is fully charged. Radiation passing through the chamber will cause the charge to leak off in proportion to the amount of radiation and move the electrometer string upscale accordingly. This upscale position indicates the amount of radiation exposure. Operating Conditions: Temperature: -20 degrees F to +140 degrees F Humidity: No effect, unit has water and dust tight seals Altitude: Independent of pressure changes from sea level to over 50,000 Ft. All metal, built to meet rigid Military Standards requirements for extremes of Temperature, Altitude, Shock and Vibrations Cover: Heavy aluminum casting Case: Drawn steel. (0.025 c.r.s.) Operating instructions on the back of this sheet

4 The Charging Process - Zeroing the Dosimeter Accumulated radiation is read directly on an internal calibrated scale of the Dosimeter. A Dosimeter Charger ( such as the Jordan 750-5) is required in order to return the dosimeter to zero after each exposure period if desired. One end of the dosimeter contains an optical eye-piece; the opposite end is sealed by a diaphragm switch which houses the insulated steel charging pin. The instrument is charged (set to zero) by pressing the charging pin onto the charging socket on the charger. When the charging end of the dosimeter is pressed firmly into the charging socket (receptacle) on the charger, the pin contacts the electrometer frame. Sufficient voltage is applied to charge up the dosimeter and to set the fiber to zero Step 1. Reading a dosimeter: Remove the cap on the charging socket by unscrewing the cap. Then press down lightly with the dosimeter on the charging socket. The light should come on. If the light does not come on it could mean there is no battery inside the charger. Replace the battery by removing the screw in the center of the faceplate.( See diagram) and installing new battery. Note the + end of the battery needs to be aligned with the + (pos) marking on the circuit board inside the charger. Arrow-Tech Model 138 dosimeter Jordan Charger Model Here you see Ron zeroing a dosimeter, notice his left hand on the adjustment knob. After he has zeroed the dosimeter, he lets up just a little to keep the light on and see if the fiber is still on zero. Step 2 While pressing the charging end of the dosimeter firmly down in the receptacle of the charger, adjust the "down-scale/up-scale" control on the charger, while looking through the dosimeter at the light that comes on until a zero reading is indicated IF the fiber is not moving, press the dosimeter farther down in the receptacle and try again. Step 3. At times, a transient "kick" is experienced when zeroing the dosimeter. The charging contact of the charger automatically compensates for the kick when the dosimeter is with drawn slowly from the contact. You can see this effect by holding the dosimeter on the charging contact while looking into the instrument. Withdraw the instrument slowly. You will note that just before the light turns off, the hairline will shift. With a little practice the hairline can be made to shift so that its final position coincides with the zero line. Optimum performance is obtained when electrostatic kick is compensated for in this manner. The hairline will remain on or near the zero position for long periods when not exposed to radiation. Step 4. When resetting the dosimeter to zero, the fiber may disappear and remain hidden. To release the fiber, slowly turn the "down scale / up scale" knob until the fiber reappears. Keep repeating steps 1 through 4 as needed. Some practice might be required to become proficient at zeroing the dosimeter. Your dosimeter should now be on zero,(0) and ready to use. When properly zeroed the fiber will remain on zero. >

5 THE CHARGER FOR DIRECT READ DOSIMETERS Charger The patented, handheld CHARGER can charge a variety of directreading dosimeters by simply squeezing the lever of a generator. The Charger requires no batteries. By pulling a trigger, a dosimeter is easily placed in or removed from the charger. The clamping action holds the dosimeter for you. Includes: 1 year limited warranty Specifications: Power: Discharge Bulb: Clamping Mechanism: Temperature Range: Humidity Range: Weight: Size: 15,000Volt Piezoelectric generator Flashes to indicate instrument is operational Adjustable and self locking. Spring loaded-applies 10 lbs of pressure. All metal parts are stainless steel Operating: -20 C to +50 C (-4 F to F) 0 to 90% Relative humidity grams (8.64 oz) x (at its widest point) x mm (6x4.2x.87 inches) THE VersaBrite LITE AVAILABLE FOR ILLUMINATION OF THE DIRECT-READ DOSIMETER