LUDLUM 19A User manual

LUDLUM MODEL 19A
Micro R Meter
May 2017
Serial No. 144020 and Succeeding
Serial Numbers

LUDLUM MODEL 19A
Micro R Meter
May 2017
Serial No. 144020 and Succeeding
Serial Numbers

Model 19A Micro R Meter
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 [phone]

Model 19A Micro R Meter
TABLE OF CONTENTS
1. GENERAL.......................................................................................................................................... 1
2. SPECIFICATIONS ............................................................................................................................ 1
3. DESCRIPTION OF CONTROLS AND FUNCTIONS................................................................... 2
4. OPERATING PROCEDURES.......................................................................................................... 2
5. CALIBRATION................................................................................................................................. 3
6. MAINTENANCE............................................................................................................................... 4
PARTS LIST........................................................................................................................................... 5
DRAWINGS AND DIAGRAMS....................................................................................................... 10

Model 19A Micro R Meter

Model 19A Micro R Meter
page 1
1. GENERAL
The Ludlum Model 19A Micro R Meter is a
portable survey instrument having the
additional feature of an audio and visual alarm.
The alarm circuit is adjustable from a meter
scale deflection of 0 to off scale. The meter
scale is logarithmic with a range of 0-500 µR/hr
or 0-5 µSv/h. (The unit is available in either
µR/hr or µSv/h.)
The Model 19A utilizes an internally-mounted
2.5 x 2.5 cm (1 x 1 in.) NaI (Tl) scintillator to
offer an optimum performance in counting low-
level gamma radiation. It is designed to be
moisture and dust resistant.
The unit body is made of cast aluminum,
including the meter housing. The meter housing
is a rugged aluminum bezel with waterproof
seals. The can is 2.3 cm (0.90 in.)
aluminum. Other operating features of the
instrument include a unimorph speaker
mounted to the instrument can with an audio
ON-OFF capability, alarm reset push-button
switch, and a three-position switch for selecting
battery check or instrument ON.
The instrument is capable of using either
standard D cell batteries or nickel-cadmium
rechargeable batteries. However, the 19A does
not include circuitry for recharging the
batteries.
All controls, including a calibration
potentiometer, are internal. Two D cell batteries
are located in an isolated compartment and
easily changed from the front panel.
2. SPECIFICATIONS
LINEARITY: ±10% of full scale
INPUT IMPEDANCE: 0.1 megohm
HIGH VOLTAGE: variable from 400-1500
Vdc, electronically regulated to within ±1%
CALIBRATION STABILITY: less than 3%
variance to battery end point
SENSITIVITY: 30 ±10 mV
BATTERY COMPLEMENT: two standard
size "D" cell batteries, secured in a isolated
compartment with screws and a gasket for dust
and moisture proofing
BATTERY LIFE: exceeds 600 hours with a
fresh set of Alkaline "D" cell batteries (non-
alarm condition)
AUDIO OUTPUT: built-in unimorph speaker
and ON-OFF switch provided on front panel
ALARM INDICATION: audio and visual
indication when above alarm threshold
ALARM RANGE: 0 to off-scale
COUNTING RANGE: 0-500 R/hr or 0-5
µSv/h
RESPONSE: dependent on number of counts
present (typically not greater than 7 seconds
from 10% to 90% of final reading)
METER: 1 mA, 6.4 cm (2.5 in.) scale, pivot-
and-jewel suspension
DETECTOR: photomultiplier coupled to a 2.5
x 2.5 cm (1 x 1 in.) NaI (Tl) crystal mounted
inside the instrument housing
FINISH: drawn-and-cast aluminum
fabrication with beige powder coating
SIZE: 19.8 x 8.9 x 21.6 cm (7.8 x 3.5 x 8.5 in.)
(H x W x L), with handle
WEIGHT: 2.1 kg (4.5 lb), including batteries

Model 19A Micro R Meter
page 2
3. DESCRIPTION OF CONTROLS AND FUNCTIONS
OFF-BAT-ON Selector Switch: A three-
position switch for turning the instrument on
and checking the battery status. A BAT TEST
scale on the meter provides a visual means of
checking the battery when the switch is in the
BAT position. The ON position provides power
to the instrument.
AUD ON-OFF Toggle Switch: In the ON
position, operates the unimorph speaker,
located on the left side of the instrument. The
frequency of the clicks is relative to the rate of
the incoming pulses. The higher the rate is,
the higher the audio frequency. The audio
should be turned OFF when not required to
reduce battery drain.
ALARM RES Pushbutton Switch: When
depressed, this switch resets the alarm when the
meter pointer is below the alarm threshold.
ALARM Light: A red lamp that comes on to
give a visual alarm when radiation is above the
alarm threshold.
4. OPERATING PROCEDURES
The Model 19A is a simple instrument to
operate. All controls are located on the front
panel along with the battery compartment. The
2.5 x 2.5 cm (1 x 1 in.) NaI (Tl) Scintillator is
mounted internally.
NOTE: To open the battery lid, twist the
lid button counter-clockwise one quarter of
a turn. To close, twist clockwise a quarter
of a turn.
Open the lid and install two "D" size
batteries. Note (+) (-) marks on the inside of
the lid. Match the battery polarity to these
marks.
NOTE: Center post of flashlight battery is
positive.
Close the battery box lid.
Select the BAT position of the OFF-
BAT-ON switch. Replace the batteries if
the meter pointer is below the BAT TEST
line.
Check for audio indication with the
AUD ON-OFF switch.
Check the instrument for the proper
meter scale indication with a known source.
NOTE: Instrument response time will vary
with the radiation field intensity. Refer to
the RESPONSE time in Section 2.
Position a check source to drive meter
to alarm set point (set at 20-50 R/hr or
0.20-0.50 µSv/h at factory) causing
instrument to alarm. Remove check source
and depress the ALARM RES pushbutton
to confirm that alarm will reset.
The instrument is ready for monitoring.

Model 19A Micro R Meter
page 3
5. CALIBRATION
The Model 19A radiation response is energy-
sensitive. The detector plateau-characteristic
must be determined for the anticipated
radiation nuclide. The following is an
example calibration:
Remove the instrument from its case
(referred to as "can" from hereon).
Adjust Alarm Set control fully
clockwise to keep the alarm circuit
from tripping during calibration.
With the instrument off, remove the
detector coax cable connection at the
junction of C57-R27 on the circuit
board.
Connect a Ludlum Model 500 Pulser
to the C57-R27 junction.
Set the pulse height at -80 mV.
Calibrate the scales as shown in Table
1. Use the CAL control for the mid
scale or lower meter reading and the
SPAN control for the upper meter
reading. Alternate between the two
controls to ensure meter linearity
between readings.
Reconnect detector coax to the
junction of C57-R27. Replace
instrument can.
NOTE: The detector is not light-tight outside
of the can.
Plateau instrument with 241Americium
using the HV adjust potentiometer.
Determine the plateau center voltage.
Remove can.
Measure detector operating voltage at
C57-R27 and record for future
reference.
NOTE: Measure high voltage with a Model
500 pulser or a high-impedance voltmeter
with a high-meg probe. If one of these
instruments is not available, use a voltmeter
with a minimum of 1000 megohm input
resistance.
Replace instrument can.
Take the Model 19A to a certified
calibration range. Place the instrument in
a 100R/hr (1 µSv/h) (exposure rate)
radiation field. The depression at the front
of the instrument can indicates the
detector axis center, and approximately
1.9 cm (0.75 in.) from the depression end
is the detector 2.5 x 2.5 cm (1 x 1 in.) NaI
scintillator center. Expose the radiation
source and adjust the CAL control
(located on the calibration board inside
instrument can) for the correct meter
indication.
Place the instrument in a calibrated 500
R/hr (5 µSv/h) radiation field. Adjust the
SPAN control for correct meter reading.
Confirm instrument linearity by placing
the instrument back in 100 R/hr (1
µSv/h) field. If the meter is non-linear,
alternate between the CAL and SPAN
controls for meter correction. Adjust the
Cal control for the lower reading and the
Table I
READING PULSES/MINUTE
5 875
50 8,750
500 87,500

Model 19A Micro R Meter
page 4
SPAN control for the upper reading.
Position meter pointer at the desired alarm
set point with radiation source. Adjust the
ALARM SET control to the desired alarm
threshold. Minimum setting is 0 on the
meter scale and maximum setting is full-
scale deflection. (Factory set at 20-50
R/hr or 0.20-0.50 µSv/h.)
When the alarm circuit is energized, both
the audio and visual indications should
occur. Depressing the ALARM RES
push-button switch resets the alarm circuit
when the meter pointer is below the alarm
threshold.
Recheck all operating functions of the
instrument prior to use.
6. MAINTENANCE
Instrument maintenance consists of keeping the
instrument clean and periodically checking the
batteries and the calibration.
An instrument operational check should be
performed prior to each use by exposing the
detector to a known source and confirming the
proper reading on each scale.
Recalibration should be accomplished after any
maintenance or adjustment of any kind has
been performed on the instrument. Battery
replacements are not considered to be
maintenance and do not normally require the
instrument to be recalibrated.
Ludlum Measurements recommends
recalibration at intervals no greater than one
year. Check the appropriate regulations to
determine required recalibration intervals.
The batteries should be removed and the battery
contacts cleaned of any corrosion at least every
three months. If the instrument has been
exposed to a very dusty or corrosive
atmosphere, more frequent battery servicing
should be used.
Use a spanner wrench to unscrew the battery
contact insulators, exposing the internal
contacts and battery springs. Removing the
handle will facilitate access to these contacts.
NOTE: Never store the instrument over 30 days without removing batteries.
Although this instrument will operate at very high ambient temperatures,
battery seal failure can occur at temperatures as low as 37.8 °C (100 °F).

Model 19A Micro R Meter
page 5
PARTS LIST
Ref. No. Description Part No.
Model 19A Ratemeter
UNIT Completely Assembled Model
19A Micro R Meter 48-2117
Circuit Board, Drawing 363 X 440
BOARD Assembled Circuit Board 5363-602
CAPACITORS
C38 0.0015F, 3KV, C 04-5518
C40 0.0015F, 3KV, C 04-5518
C41 0.0015F, 3KV, C 04-5518
C42 0.0027F, 3KV, C 04-5520
C50 100pF, 3KV, C 04-5532
C56 100F, 10V, DT 04-5576
C57 100pF, 3kV, C 04-5532
C102 100F, 10V, DT 04-5576
C103 10F, 20V, DT 04-5592
C106 0.001F, 100V, C 04-5519
C109 0.01F, 100V , C 04-5523
C112 470pF, 100V, C 04-5555
C113 0.01F, 100V, C 04-5523
C115 100F, 10V, DT 04-5576
C117 100pF, 100V, C 04-5527
C119 0.001F, 100V, C 04-5519
C121 330pF, 100V, C 04-5531
C126 10F, 20V, DT 04-5592
C134 100F, 10V, DT 04-5576
C163 0.01F, 100V, C 04-5523
C170 0.1F, 100V, C 04-5521
C171 1F, 35V, DT 04-5575
C191 0.0015F, 3KV, C 04-5518
C200 4.7F, 10V, DT 04-5578
C226-C227 0.01F, 100V, C 04-5523
C228 0.1F, 35V, DT 04-5574
TRANSISTORS
Q6 2N3904 05-5755
Q15 MPS6534 05-5763

Model 19A Micro R Meter
page 6
Q44 2N3904 05-5755
Q96 2N3904 05-5755
Q145 MPS6534 05-5763
Q218 MPSW01 05-5778
Q224 MPS6534 05-5763
Q225 2N3904 05-5755
INTEGRATED CIRCUITS
U1 CA3096 06-6023
U2 TLC372 06-6265
U3 CD4098 06-6066
U4 CA3096 06-6023
U5 ICM7555 06-6136
U6 TLC27M7IP 06-6248
U7 MAX631 06-6249
U101 LM385Z-1.2 05-5808
U198 TLC27M7IP 06-6248
DIODES
CR94 1N4148 07-6272
CR166-CR167 1N4007 07-6274
CR169 1N4007 07-6274
CR175 1N4007 07-6274
CR201-CR202 1N4148 07-6272
RESISTORS
R18 1k 10-7009
R27 22k 10-7070
R36 10M 10-7031
R46 10k 10-7016
R47 1G 12-7686
R63 82k 10-7022
R64 1k 10-7009
R65 10k 10-7016
R66 1k 10-7009
R68 8.2k 10-7015
R70 4.7k 10-7014
R72 SAT (TYPICALLY 33k for µR
version and 82k for µSv
version)
R75 33k 10-7019
R76 100 OHM 10-7004
R77 2.2k 10-7012
R78 22k 10-7070
R79 100k 10-7023

Model 19A Micro R Meter
page 7
R81 10k 10-7016
R83 100k 10-7023
R84 470k 10-7026
R86 2.7M 10-7029
R87 10k 10-7016
R89 100k 10-7023
R91 4.7k 10-7014
R128 100k 10-7023
R137 10k 10-7016
R138 1M 10-7028
R147 SAT (TYPICALLY 750k)
R150 SAT (TYPICALLY 2.2k)
R159 10k 10-7016
R172 47k 10-7020
R177 200 OHM 10-7006
R189 200 OHM 10-7006
R196 1k 10-7009
R204 1M 10-7028
R205 1OOk 10-7023
R206 22k 10-7070
R207 5.6k 10-7042
R208 24.3k 12-7700
R209-R210 294k 12-7632
R212 100k 10-7023
R213 1k 10-7009
R214 24.3k 12-7700
R215 SAT (TYPICALLY 10k)
R216-R217 100M 10-7036
TRANSFORMERS
T165 L8050 40-0902
INDUCTORS
L13 IM6-470UH-5 21-9600
MISCELLANEOUS
* CLOVERLEAF RECEP-
TACLES 011-6809 (6 EACH) 18-8771
* WALDON 16-06-0007 LAR-
GE RECEPTACLE 18-8792
* JACK-TEST 1128-09-0319 18-8806
*
SPACER-423-175 (2 EA) 18-8992

Model 19A Micro R Meter
page 8
Calibration Board, Drawing 367 x 48
BOARD Assembled Calibration Board 5367-064
RESISTORS
R1-R2 100k TRIMMER 09-6823
R3 500 OHM TRIMMER 09-6848
R4 10k 10-7016
R5 100k TRIMMER 09-6823
R6 100k 10-7023
MISCELLANEOUS
P1 CONN-640456-8 MTA100 13-8039
Wiring Diagram, Drawing 367 X 47
AUDIO
DS2 UNIMORPH 101-001 21-9251
CONNECTORS
J1 CONN-1-640442-3 MTA100 13-8138
J2 CONN-640442-2 MTA100 13-8178
J3 CONN-640442-8 MTA100 13-8184
SWITCHES
S1 PA-600-210 08-6501
S2 30-1-PB GRAYHILL 08-6517
S3 7101-SYZ-QE 08-6511
BATTERY
B1-B2 BATTERY-DURACELL "D" 21-9313
MISCELLANEOUS
DS1 BULB-3338 21-9307
* LAMP-HOLDER
101-8430-09-201 21-9410
* LENS-RED 140-1471 21-9411
M1 PORT BEZEL W/MOV ASSY 4363-188
* METER BEZEL W/GLASS
W/O SCREWS 4363-352

Model 19A Micro R Meter
page 9
* METER MVMNT
919492 1 mA 15-8030
* M19A BATTERY BOX LID
W/CE 9367-125
* BATTERY CONTACT ASSY 2001-042
* DEEP PORTABLE CAN
ASSY 4363-615
* M19A CASTING 9367-055
* M19A MAIN HARNESS 8367-065
* PORTABLE KNOB 08-6613
* BATTERY LID W/LATCH
SET 9367-032
* PORT LATCH KIT W/O
BATTERY LID 4363-349
* SWITCH SEAL (TOGGLE) 08-6610
* SWITCH SEAL (P/B) 08-6611
* REPLACEMENT DETECTOR
ASSY 47-1574
* X-TAL TUBE ASSY- M12S 2004-061
* PM TUBE 2.9 cm (1.1 in.) 01-5367
* CAL COVER W/SCREWS 9363-200

Model 19A Micro R Meter
page 10
DRAWINGS AND DIAGRAMS
Front of Manual:
Model 19A Micro Sieverts Front Panel, Drawing 367 x 167
Back of Manual:
*Main Board, Drawing 363 x 440
*Main Board Component Layout, Drawing 363 x 441
Calibration Board, Drawing 367 x 48
Calibration Board Component Layout, Drawing 367 x 150
Wiring Diagram, Drawing 367 x 47
* Handwritten changes were made on these drawings for the µSv version of this instrument.