J13 HANDBOOK
ISORAC
MODEL 844
Isotech North America
158 Brentwood Drive, Unit 4
Colchester, VT 05446
Phone: (802)-863-8050
Fax: (802)-863-8125
www.isotechna.com
sales@isotechna.com
The company is always willing to give technical advice and
assistance where appropriate. Equally, because of the
programme of continual development and improvement we reserve
the right to amend or alter characteristics and design without
prior notice. This publication is for information only.
The NAMAS logo shown in the corner of the pages in this
report/handbook is to inform readers of our accreditation
number only and does not imply endorsement by UKAS of the
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J13 HANDBOOK
information herein. Please refer to our Website for our
latest UKAS Accredited Schedule.
CONTENTS
PAGE NO:
1. Introduction 3
2. Specification 4
3. Theory of Operation 5
4. Operating Instructions 6
5. Trouble Shooting Guide 7
6. Key to Input/Output Terminations &
Thermocouple Connection Diagram 8
7. Parts List 9,10+11
8. Spare Parts Price List 12
9. Data Sheet for J13 13
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DRAWINGS
DRAWING:NO:
10. Assembly Drawing X844-20-01
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J13 HANDBOOK
11. Insulation Assembly W844-20-02
12. Wire Connection Diagram X844-20-03
13. Circuit Diagram W844-20-04
14. Outline Drawing X844-20-05
INTRODUCTION:
These units were specifically designed to eliminate the need
for ice baths or thermal blocks (ovens) at the reference
junctions of Thermocouples.
In an Isothermal system cold junctions are inserted into a
block of uniform temperature, which is insulated, and slowly
tracks ambient temperature.
A separate signal is generated to indicate the metal block
temperature.
Isothermal systems are the most common type for Instruments,
Data Acquisition and Computer Systems.
Power is supplied from an AC or DC supply as specified. The
power supplied operates a power supply card which feeds a
miniaturised solid state device, this produces a thermal
E.M.F. which is added to the thermocouple output in the
software of a data logger.
Uniformity, a critical factor in the comparison of
thermocouples, is obtained by using junctions constructed of
selected premium grade thermocouple wire to produce consistent
output from the first to the last junction.
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J13 HANDBOOK
This unit is for standard 19 inch rack mounting and can
accommodate up to 100 channels. All terminations are sited at
the rear of the unit. Incoming thermocouple connections are
via klippon terminals and outgoing copper connections are via
plugs and socket (see wire connection drawing and outline
drawing at rear of manual).
SPECIFICATION:
Thermocouple Wire To ASTM (E230 Special and
BS
1041 Specification)
Junctions 2 Welded Junctions per
reference channel i.e.,
Junction 1 - Ni/Cr to Cu
+ve
Junction 2 - Ni/Al to Cu -
ve
Capacity Up to 100 Channels
Size: Width: 483mm (19")
Height: 255mm (10")
Depth: 312mm (12")
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J13 HANDBOOK
Weight: (Nett) 12 Kgs (26lbs)
Power Supply As Specified
Temperature Gradient .05°C between probes (max)
.05°C between junctions
(max)
Ambient Temperature Range -20°C to +70°C
Temperature Uniformity ±0.01°C
Accuracy According to agreed
specification
(Typically better then
±0.1°C per 10°C
change in ambient
temperature
Long Term Stability Better than ±0.1°C per 1000
hours over
temperature not exceeding
20°C increasing of 10°C on
operating temperature
range (assuming no supply
voltage variations). Allow
±0.05°C per 1000 hours for
power supply model.
THEORY OF OPERATION
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J13 HANDBOOK
If the temperature of the reference junction of a thermocouple
is allowed to change, the output emf will vary in accordance
with the seeback coefficient of the couple at the reference
temperature. A compensating circuit containing a source of
current, a combination of fixed resistors, and a temperature
sensitive element can be designed which will have a similar
variation of emf as the temperature of the circuit is varied.
If the reference junction of the thermocouple is coupled
thermally to the circuit and the compensating circuit is
connected in series with the thermocouple so that its
temperature variable emf opposes that caused by the reference
junction, the thermocouple behaves as if the reference
junction temperature were held constant. In addition, by
suitable choice of the fixed resistors, any fixed reference
junction temperature may be simulated. Since the circuit is
at the temperature of the reference junctions, no warm-up or
stabilization time is involved.
In the J11 or J13, all the thermocouples are routed to device
called an Isothermal Block where each of the thermocouple
conductors is joined to a copper wire which is routed to the
emf measuring instrument.
Within the Isothermal Block all of the reference junctions
between the thermocouple conductors and the copper wires are
insulated electrically but kept in good mutual thermal contact
with each other and with a circuit such as the one described
above which compensates for the temperature within the
Isothermal Block.
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J13 HANDBOOK
OPERATING INSTRUCTIONS
1. Connect thermocouple inputs and outputs to the desired
channel terminals. Be certain that polarity and materials are
correctly connected. Also connect output from ISOCOMP units
to measuring or scanning equipment (see key to output/input
terminations [Page 7] and wire connection drawings).
2. For Mains Operated Units
a) Connect mains input supply via connection on back of unit,
checking that the correct voltage is being used, either
220/240v 50Hz, single phase or 110/115v 50Hz single phase.
b) The earth switch on the panel refers to an earth
connection to the block which can either be floating or
connected to chassis earth as required.
c) After making all connections energise the unit by pushing
switch marked "Power On", the neon should then indicate this
state. Allow three minutes for stabilisation of internal
power supply.
3) For 24v Dc Operated Units
a) The unit need only be switched on as required
(stabilisation is immediate). To increase the life of the
battery, the unit should be switched off after use.
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J13 HANDBOOK
TROUBLE SHOOTING GUIDE
Malfunctions involving the reference junction will usually be
open and short circuits between channels or the reference
block. Simple continuity checks with a Ohm-meter will reveal
these faults, use earth continuity switch.
Calibration Faults
If the unit does not give the specified accuracy, then the
following points should be considered.
1. Are the junctions making good thermal contact with
reference block?
2. Has enough heat sink compound been used in the holes?
3. Are all input/output termination screws tightened?
4. The output of the internal power supply should be about
1.350V. This voltage is factory set. If the ISOCOMP output is
incorrect it can be brought back within specification by
slightly adjusting the Potentiometer on the Power Supply
Board.
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J13 HANDBOOK
5. Are the correct standards being used for the thermal emf
calibration tables?
KEY TO INPUT/OUTPUT TERMINATIONS
Incoming thermocouple wires will be colour coded to correspond
with British Standards requirements in most cases. i.e.
Nickel/Chromium -
+Brown
Nickel/Aluminium - Blue
NOTE: We may deviate from these colours for our internal
thermocouple loom because certain elements have the same
colour coding, i.e. Nickel/Aluminium and Constantan.
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J13 HANDBOOK
Output terminations are usually coded red and blue, positive
and negative respectively.
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SCHEMATIC THERMOCOUPLE CONNECTION DIAGRAM
Example showing connections for Ni/Cr - Ni/Al thermocouple
channel.
INPUT TERMINALS OUTPUT TERMINALS
PARTS LIST, ASSEMBLY DRAWING, X844/20/01
PART NO: DIAGRAM REFERENCE DESCRIPTION
SPECIFICATION
OR CIRCUIT REFERENCE
Y884-01-01/02 1 Front Panel (Large)To
I.T.L. Specification
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J13 HANDBOOK
Y884-01-03/04 1 Front Panel (Small)To
I.T.L. Specification
Z828-01-03 2 Chassis
To I.T.L.
Specification
X828-01-04 3 Side Panel (Large) Pair
To I.T.L.
Specification
X828-01-05 3 Side Panel (Small) Pair
To I.T.L.
Specification
X828-01-06 4 Top Cover
To I.T.L. Specification
X828-01-07 5 Bottom Cover
To I.T.L. Specification
X828-01-08 6 Back Panel (Large) T o
I.T.L. Specification
X828-01-09 6 Back Panel (Small) T o
I.T.L. Specification
X839-01-07 7 Shield Section (Large)To
I.T.L. Specification
X839-01-06 7 Shield Section (Small)To
I.T.L. Specification
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J13 HANDBOOK
W828-01-12 8 Assembly Rail To I.T.L. Specification
W828-01-13 9 RH. Rail Bracket To I.T.L. Specification
W828-01-14 10 LH Rail Bracket To I.T.L. Specification
PARTS LIST, ASSEMBLY DRAWING., X844-02-01
PART NO: DIAGRAM REFERENCE DESCRIPTION SPECIFICATION
OR CIRCUIT
REFERENCE
935-16-38 11 Socket (Male Receptacle) (Amphenol, 7 Pine Type T
3105000)
935-11-11 12 Fuse Holder Belling Lee Type L1596
935-12-22 13 Fuse Link Belling Lee Type L562 1
Amp
935-30-17 14 End Brackets Klippon Type EWK 12062
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J13 HANDBOOK
935-30-16 15 End Section Klippon Type AP1509
935-30-15 16 Terminals Klippon Cat. 2155 S.A.K.N.
935-27-06B 17 Mains Switch Arrow 10 AMP 2600/12E
935-34-19B 18 Neon Red Arrow 110 Volt 1606/R11E
935-34-23B 18 Neon Red Arrow 240 Volt 1609R21E
844-05-01 PCB Assembly 1.5 Volt
PARTS LIST (INSULATION ASSEMBLY DRAWING NO: X844-20-02
PART NO: DIAGRAM REFERENCE OR DESCRIPTION SPECIFICATION
CIRCUIT REFERENCE
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X844-01-00 1 Block Assembly To I.T.L. Specification
(to suit application)
W822-01-07 2 Retaining Plate To I.T.L. Specification
W828-02-06 3 Outer Insulation To I.T.L. Specification
W828-02-07 4 Insulation Spacer To I.T.L. Specification
W828-02-08 5 Insulation Spacer To I.T.L. Specification
W828-02-09 6 Insulation Disc To I.T.L. Specification
W828-02-10 7 Insulation Disc To I.T.L. Specification
W828-02-12 8 Insulation Disc To I.T.L. Specification
932-20-02 9 Spacer To I.T.L. Specification
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Notes
KOOBDNAH 31J
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J13 HANDBOOK
SPARE PARTS PRICE LIST
J11 AND J13 THERMOCOUPLE REFERENCING UNITS
DESCRIPTION PART NO:
Block Assembly with one X844-02-00
Measuring Module
Fuse Link (Pack of 10) 935-12-22
Fuse Holder 935-11-11
Rocker Switch 935-27-06B
Lamp (RED) 240V 935-34-23B
Lamp (RED) 110V 935-34-19B
PCB Assembly W844-05-00
Plug 935-16-37
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