Ludlum Measurements 12 Manual de usuario

LUDLUM MODEL 12

SURVEY METER

July 2017

Serial Number 218039 and Succeeding

Serial Numbers

LUDLUM MODEL 12

SURVEY METER

July 2017

Serial Number 218039 and Succeeding

Serial Numbers

Ludlum Measurements, Inc. July 2017

STATEMENT OF WARRANTY

Ludlum Measurements, Inc. warrants the products covered in this manual to be free of

defects due to workmanship, material, and design for a period of twelve months from

the date of delivery. The calibration of a product is warranted to be within its

specified accuracy limits at the time of shipment. In the event of instrument failure,

notify Ludlum Measurements to determine if repair, recalibration, or replacement is

required.

This warranty excludes the replacement of photomultiplier tubes, G-M and

proportional tubes, and scintillation crystals which are broken due to excessive

physical abuse or used for purposes other than intended.

There are no warranties, express or implied, including without limitation any implied

warranty of merchantability or fitness, which extend beyond the description of the

face there of. If the product does not perform as warranted herein, purchaser’s sole

remedy shall be repair or replacement, at the option of Ludlum Measurements. In no

event will Ludlum Measurements be liable for damages, lost revenue, lost wages, or

any other incidental or consequential damages, arising from the purchase, use, or

inability to use product.

RETURN OF GOODS TO MANUFACTURER

If equipment needs to be returned to Ludlum Measurements, Inc. for repair or calibration, please

send to the address below. All shipments should include documentation containing return shipping

address, customer name, telephone number, description of service requested, and all other necessary

information. Your cooperation will expedite the return of your equipment.

LUDLUM MEASUREMENTS, INC.

ATTN: REPAIR DEPARTMENT

501 OAK STREET

SWEETWATER, TX 79556

800-622-0828 325-235-5494

FAX 325-235-4672

Ludlum Measurements, Inc. July 2017

Table of Contents

Introduction 1

Getting Started 2

Unpacking and Repacking 2-1

Battery Installation 2-1

Connecting a Detector to the Instrument 2-2

Battery Test 2-2

Instrument Test 2-2

Reading the Meter Face Dial 2-3

Operational Check 2-6

Specifications 3

Identification of Controls and Functions 4

Safety Considerations 5

Environmental Conditions for Normal Use 5-1

Warning Markings and Symbols 5-1

Cleaning and Maintenance Precautions 5-2

Calibration and Maintenance 6

Calibration 6-1

True Reading Calibration 6-1

Internal Calibration after overhaul 6-2

Establishing an Operating Point 6-3

Maintenance 6-4

Recalibration 6-5

Batteries 6-5

Troubleshooting 7

Troubleshooting Electronics which utilize a

GM, Scintillator, or Proportional Detector 7-1

Troubleshooting GM Detectors 7-3

Model12 TechnicalManual

Ludlum Measurements, Inc. July 2017

Troubleshooting Scintillators 7-4

Troubleshooting Proportional Detectors 7-4

Technical Theory of Operation 8

Main Board (Drawing 464 × 275 3 sheets) 8-1

Input 8-1

Amplifier 8-1

Discriminator 8-1

Audio 8-1

Scale Ranging 8-2

Digital Analog Converter 8-2

Ratemeter Drive Circuit 8-2

HV Meter Drive 8-2

Battery Test 8-2

HV Power Supply Board (Drawing 464 × 243) 8-3

Switching Convertor 8-3

Feedback 8-3

Voltage Control 8-3

Filtering 8-3

Recycling 9

Parts List 10

Model 12 Survey Meter 10-1

Main Board, Drawing 464 × 275 10-1

HV Power Supply Board, Drawing 464 × 243 10-4

Wiring Diagram, Drawing 464 × 309 10-5

Drawings and Diagrams 11

Model12 TechnicalManual Section1

Ludlum Measurements, Inc. Page 1-1 July 2017

Introduction

he Model 12 is a portable survey meter with four linear ranges used

in combination with exposure rate or CPM meter dials. The

instrument features a regulated high-voltage power supply,

unimorph speaker with audio ON-OFF capability, fast-slow meter

response, meter reset button, and a six-position switch for selecting battery

check or range multiples of ×1, ×10, ×100, and ×1000. Each range

multiplier has its own calibration potentiometer. The unit body and meter

housing are made of cast aluminum, and the can is 0.23 cm (0.09 in.) thick

aluminum.

The audio provides a brief “click” for every radiation event detected. It also

provides a steady tone to warn the user of a low-battery condition. This low

battery warning overrides the position of the AUD ON-OFF switch.

With an adjustable detector voltage of 400-2500 volts and adjustable

discriminator of 1-100 millivolts, this unit can be operated with most

proportional, scintillation, or GM detectors. Scintillation detectors will

require voltage divider circuit resistance in excess of 50 megohms.

The unit is operated with two ˝D˝cell batteries for operation -20 to 50 °C (-4

to 122 °F). For instrument operation below 0 °C (32 °F), either very fresh

alkaline or rechargeable NiCd batteries should be used.

Section

Model12 TechnicalManual Section2

Ludlum Measurements, Inc. Page 2-1 July 2017

Getting Started

Unpacking and Repacking

Remove the calibration certificate and place it in a secure location. Remove

the instrument and accessories (batteries, cable, etc.) and ensure that all of

the items listed on the packing list are in the carton. Check individual item

serial numbers and ensure calibration certificates match. The Model 12 serial

number is located on the front panel below the battery compartment. Most

Ludlum Measurements, Inc. detectors have a label on the base or body of

the detector for model and serial number identification.

Important!

If multiple shipments are received, ensure that the detectors

and instruments are not interchanged. Each instrument is

calibrated to specific detectors, and therefore not

interchangeable.

To return an instrument for repair or calibration, provide sufficient packing

material to prevent damage during shipment. Also provide appropriate

warning labels to ensure careful handling. Include detector(s) and related

cable(s) for calibration.

Every returned instrument must be accompanied by an Instrument Return

Form, which can be downloaded from the Ludlum website at

www.ludlums.com. Find the form by clicking the “Support” tab and

selecting “Repair and Calibration” from the drop-down menu. Then choose

the appropriate Repair and Calibration division where you will find a link to

the form.

Battery Installation

Ensure the Model 12 range selector switch is in the OFF position. Open the

battery lid by pushing down and turning the quarter-turn thumbscrew

Section

Model12 TechnicalManual Section2

Ludlum Measurements, Inc. Page 2-2 July 2017

counterclockwise a quarter of a turn. Install two ˝D˝size batteries in the

compartment.

Note the (+) and (-) marks inside the battery door. Match the battery

polarity to these marks. Close the battery box lid, push down, and turn the

quarter-turn thumb screw clockwise a quarter of a turn.

Note:

The center post of a “D” size battery is positive.

Connecting a Detector to the Instrument

Caution!

The detector operating voltage (HV) is supplied to the detector

via the detector input connector. A mild electric shock may

occur if you make contact with the center pin of the input

connector. Switch the Model 12 range selector switch to the

OFF position before connecting or disconnecting the cable or

detector.

Connect one end of a detector cable to the detector by firmly pushing the

connectors together while twisting clockwise a quarter of a turn. Repeat the

process in the same manner with the other end of the cable and the

instrument.

Battery Test

Check the batteries daily or prior to use, whichever is less frequent, to assure

proper operation of the instrument. Move the range multiplier switch to the

BAT position. Ensure that the meter needle deflects to the battery check

portion on the meter scale. If the meter does not respond, check to see if the

batteries have been correctly installed. Replace the batteries if necessary.

Instrument Test

After checking the batteries, turn the instrument range switch to the ×1000

position. Place the AUD ON-OFF switch in the ON position. Expose the

detector to a check source. The instrument speaker should emit ˝clicks˝

relative to the rate of counts detected. The AUD ON/OFF switch will silence

Model12 TechnicalManual Section2

Ludlum Measurements, Inc. Page 2-3 July 2017

the audible clicks if in the OFF position. It is recommended that the AUD

ON/OFF switch be kept in the OFF position when not needed in order to

preserve battery life.

The detector cable can be a source of problems. Test the detector cable by

bending and flexing either end of the cable and checking for an increase in the

rate of counts detected. Replace the cable if an increase in the rate of counts is

detected.

Check the meter reset function by depressing the RES pushbutton switch and

ensuring the meter needle drops to “0.”

Once this procedure has been completed, the instrument is ready for use.

Reading the Meter Face Dial

Reading the meter face is very important for consistent measurements. There

are, in general, three types of meter faces: 1) count rate (typically cpm [counts

per minute]); 2) exposure rate (typically mR/hr); and 3) “combo” (typically

cpm and mR/hr). The following examples are intended to help the user

interpret the correct reading.

The normal procedure is to turn the range selector switch to the highest range

and if no readings are seen on the meter, turn the selector switch down to the

lower scales until a reading is seen. The ranges on the instrument selector

switch are multipliers for the meter reading. A typical single scale (one arc)

meter face with a cpm (counts per minute) dial is shown below.

The count rate scale reads 0-5K COUNTS/MINUTE (kcpm or 1000’s of

counts per minute) and has BAT TEST on the dial.

If the needle is pointing as indicated below and the instrument range

selection switch is on the ×0.1 scale multiple, then the reading is 3.5 kcpm

(multiplied by) × 0.1 = 350 cpm.

Model12 TechnicalManual Section2

Ludlum Measurements, Inc. Page 2-4 July 2017

The same needle indications on successive ranges would be:

×1 = 3.5 kcpm (or 3500 cpm)

×10 = 35 kcpm (or 35,000 cpm)

×100 = 350 kcpm (or 350,000 cpm)

A typical dual scale (two arcs) meter face is shown below. The top scale

reads 0-2 mR/hr. The bottom scale also reads 0-2 mR/hr and is for ×100

scale only. The ×100 ONLY scale will work correctly when the multiplier

switch is in the ×100 range. The meter face also has a BAT TEST position

on the dial.

If the needle is pointing as indicated below and the range selection switch

is on the ×0.1 scale, then the reading is 0.1 mR/hr.

The same needle indications on successive ranges would be:

×1 = 1.0 mR/hr (or 1,000 µR/hr)

×10 = 10 mR/hr (or 10,000 µR/hr)

×100 = 70 mR/hr (or 70,000 µR/hr)

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