Fisher Scientific 650 Series User manual

Isotemp®Programmable Muffle
Furnace
650-750 Series
Instruction Manual
Model 14
Catalog No.
10-650-14 & 14A, 10-750-14 &14A
10-650-14C & 14AC, 10-750-14C & 14AC
Model 58
Catalog No.
10-650-58, 10-750-58
10-650-58C, 10-750-58C
Model 126
Catalog No.
10-650-126, 10-750-126
10-650-126C, 10-750-126C
103770 • 1/25/06

Table of Contents
Safety Information ..............................................................................................................................................3
Alert Signals..................................................................................................................................................3
Introduction..........................................................................................................................................................4
Installation ..........................................................................................................................................................5
Selecting a Location ....................................................................................................................................5
Unpacking ....................................................................................................................................................5
Preparing the Furnace ..................................................................................................................................6
Figure 1-Furnace Layout ....................................................................................................................................7
Controls ..............................................................................................................................................................8
Displays ........................................................................................................................................................8
Set Display ............................................................................................................................................8
Actual Display ........................................................................................................................................8
Heat LED ......................................................................................................................................................8
Alarm LED ....................................................................................................................................................8
Run LED ......................................................................................................................................................8
Keypads ........................................................................................................................................................9
Circulating Fan (Model 750 only)..................................................................................................................9
Operation ..........................................................................................................................................................10
Control Mode ..............................................................................................................................................10
Ramp and Soak Mode................................................................................................................................10
Program Step..............................................................................................................................................11
Creating a Ramp and Soak Program ........................................................................................................12
Running, Stopping or Resuming a Program ..............................................................................................15
Viewing Program Status ............................................................................................................................16
Set Point or Soak Step ..............................................................................................................................17
An Example Program..................................................................................................................................17
High Temp Alarm ..............................................................................................................................................20
Open Thermocouple..........................................................................................................................................20
Calibration ........................................................................................................................................................20
Units ..................................................................................................................................................................21
Power Failure ....................................................................................................................................................21
Data Logging ....................................................................................................................................................22
Serial Communication ......................................................................................................................................22
Troubleshooting ................................................................................................................................................24
Service ..............................................................................................................................................................25
Replacing a Heater ....................................................................................................................................25
Replacing the Control Thermocouple ........................................................................................................26
Replacing the Solid State Relay ................................................................................................................27
Replacing the Magnetic (Safety) Relay ......................................................................................................28
Replacement Parts............................................................................................................................................29
Accessories and Supplies ................................................................................................................................30
Performance Characteristics/Specifications......................................................................................................31
Wiring Diagram..................................................................................................................................................32
Warranty ............................................................................................................................................................36

3
Your Fisher Isotemp®Programmable Muffle Furnace has
been designed with function, reliability, and safety in
mind. It is your responsibility to install it in conformance
with local electrical codes. It is most important that the
user follow installation instructions exactly as written.
Failure to do so is likely to lead to improper operation,
erroneous calibrations and possible damage to the equip-
ment. Do not attempt operation without this information.
When operating the furnace, always observe the following
Safety Precautions:
• Wear insulating gloves.
• Use tongs.
• Use Safety goggles.
• Never stand in front of an open furnace.
• Use the supplied hearth plate on the chamber
bottom
Safety Information
Warning
Warnings alert you to a possibility of
personal injury.
Caution
Cautions alert you to a possibility of
damage to the equipment.
Note
Notes alert you to pertinent facts and
conditions.
Hot Surface
Hot surfaces alert you to a possibility
of personal injury if you come in con-
tact with a surface during use or for a
period of time after use.
Alert Signals

4
Introduction
Fisher Isotemp 650/750 Series Programmable Muffle
Furnaces are available in three sizes: small (Model 14),
medium (Model 58) and large (Model 126). All models
provide PID microprocessor temperature control at oper-
ating temperatures from 50 to 1125 °C (90 to 2057 °F).
Furnace chambers are molded from alumina silicate
ceramic fibers. Use of this material provides low thermal
mass for fast heat-up and cool-down, as well as an
unusually low exterior furnace temperature for safe opera-
tion. The furnace is heated by electric resistance ele-
ments embedded in easily removable side and base pan-
els. The heating elements are designed to ensure
extended service life, even in atmospheres characteristic
of high-sulfur coal and coke samples.
Temperature readouts and control parameters are shown
on two red 7-segment displays. Two LED's indicate when
heater power is being applied or when an over-tempera-
ture error condition is encountered. Temperatures can be
displayed in either °C or °F.
For operation with chamber atmospheres other than air
(N2, C02, etc), external gas supplies connect easily
through a provided 3/8-inch port. An Injection Port Kit
(10-550P) connected to the exhaust port allows
convenient venting of the chamber.
Isotemp furnaces incorporate a variety of safety features.
When the furnace door is opened, power is automatically
cut to the chamber heating elements. The heater power is
also cut out when the chamber temperature exceeds the
set temperature by 25°C (45°F) or more. The alarm con-
dition is indicated on the display while the alarm LED is
lit. A ventilated base design prevents damage to the
bench or countertop.
The system microprocessor permits the user to customize
a heating program of up to 24 ramp and soak steps. The
model 750 can store four 24 step programs, while the
model 650 can store one 24 step program. If desired,
a soak period of up to 23 hours, 59 minutes and 59 sec-
onds may be interspersed between any two successive
ramps.

Selecting a Location
Choose a location for the furnace, which will provide an
area of approximately four square feet (2 ft x 2 ft). The
bench or table selected must be capable of supporting at
least 60lbs for the Model 14, 90lbs for the Model 58 or
110lbs for the Model 126. Appropriate electrical power
must be available. Locate the furnace within three feet of
the power outlet so that no extension cord is required.
It is recommended that the site have facilities for venting
an accessory Exhaust Tube Assembly (Cat. No.10-490-
10) which is available for use with the furnace.
Alternatively, the furnace may be located in a fumehood if
samples are expected to produce toxic volatiles.
Unpacking
Fisher Isotemp Muffle Furnaces are shipped in a single
carton. After unpacking, locate each item shown in the list
below. Report any missing items, by name and part num-
ber, to your Fisher branch or representative. In the event
of shipping damage, retain the carton and packing materi-
al and file a claim with the final carrier.
Item
Furnace Assembly
Model 14 120 V, 50/60 Hz
Model 14A 208/240V, 50/60 Hz
Model 58 208/240 V, 50/60 Hz
Model 126 208/240 V, 50/60 Hz
Hearth Plate
Shelf (Model 126 Only)
Instruction Manual
Warranty Card
5
Installation
Caution
Do not install closer than 6 inches
to a wall of combustible material.

6
Preparing the Furnace
To prepare the muffle furnace for operation, perform the
following procedures:
1. Make certain all packing material is removed
from furnace chamber.
2. Place hearth plate on the bottom of the cham-
ber. Orient hearth plate such that smooth sur-
face faces upward. See Fig. 1, Page 7.
3. With the Model 126, the supplied shelf may be
used. If desired, install shelf by sliding it onto
top of ledge protruding from each side of the
inner chamber walls.
4. If installing the accessory Exhaust Tube
Assembly, first locate exhaust port at top of fur-
nace (see Fig 1). Use three screws to secure
the port flange to the exhaust port. Attach tub-
ing to port flange using a hose clamp (provided).
Finally, route free end of tube to fumehood or
other outside vent. If desired, exhaust tube may
be cut to length using a hacksaw.
INSTALLATION
Warning
Isotemp Muffle Furnace chambers
contain alumina silicate ceramic fibers.
With continued use at temperatures
above 1000°C (1832 °F), these materi-
als slowly convert to crystalline silica
(cristobalite). Long-term exposure to
airborne cristobalite may result in
severe respiratory diseases in
humans. Tests with laboratory animals
suggest that cristobalite is a possible
carcinogen. Short-term effects may
include irritation to skin, eyes and the
respiratory tract. Please consult the
Material Safety Data Sheet (MSDS)
provided by Fisher Scientific for further
information.
Warning
This unit is not explosion proof. Do
not use in the presence of flammable
or combustible materials; fire or explo-
sion may result. Unit contains compo-
nents that may ignite such materials.

Figure 1 – Furnace Layout
7
INSTALLATION
1 Circulating Fan Switch (Model 750) 7 Program Run Key
2 Heater LED 8 Set Temp Display
3 Menu Key 9 Alarm LED
4 Increase Key 10 Actual Temp Display
5 Decrease Key 11 Power Switch
6 Program Run LED 12 Door Switch
NOTE: The air in port is closed for Model 650 Furnaces.
See the following pages for keypad/display descriptions.

The following sections briefly describe the locations and
functions of various display fields and keypad controls.
More detailed descriptions are provided, when required,
in the operating sections of the manual.
Displays
The 650/750 Series controller features two bright, one-
half inch LED numeric displays used in setting up the fur-
nace program or reading out the furnace temperature.
Two smaller LED's indicate, respectively, an alarm
condition or when power is being applied to the furnace
heaters. Each display field is discussed separately below.
Set Display
In the Control and Ramp and Soak modes, shows the
furnace set temperature. During setup and programming,
indicates control parameters to be set.
Actual Display
In the Control and Ramp and Soak modes, shows the
actual furnace temperature. During setup and program-
ming, indicates the numerical value assigned to the cur-
rently displayed control parameter.
Heat LED
Lights when controller is calling for heat.
Alarm LED
Lights if the actual furnace temperature exceeds the set
temperature by 25°C (45°F).
Run LED
Lights when the furnace is running a ramp/soak program.
8
Controls

Keypads
The 650/750 Series incorporates a four-key, tactile key-
pad. The function of each key is discussed individually
below. See Fig. 1 for keypad locations.
During programming or setup, successively
pressing the MENU key causes the controller
display to sequentially step through menu selec-
tions.
In Control mode, pressing the UP Arrow key,
increases the furnace set temperature, as indi-
cated on the Set display. During programming or
setup, used to step through menu options.
In Control mode, pressing Down Arrow key,
decreases the furnace set temperature, as indi-
cated on the Set display. During programming
or setup, used to step through menu options.
Pressing the RUN key alternates muffle furnace
operation between the Control and Ramp and
Soak modes.
Circulating Fan (Model 750 only)
Just above and to the left of the Actual Display is the
power switch for the Circulating Fan. When turned on,
outside air is circulated through the bottom of the furnace
chamber under the hearth, were it is heated, and into the
furnace chamber. Two to four air changes per hour can
be expected with the fan on.
9
CONTROLS
MENU
RUN



The 650/750 Muffle Furnaces feature two modes of
operation:
• Control
• Ramp and Soak
Each is discussed separately in the following sections.
Control Mode
In Control mode, the muffle furnace maintains a set tem-
perature until that set temperature is changed.
To set a temperature and initiate Control mode operation,
perform the following:
1. Place the power switch in the ON position.
2. If the Run LED is lit or blinking, press Run key
until the indicator remains off.
3. Observe the set temperature in the Set Display
window.
4. To increase the set temperature, press the UP
arrow key.
5. To decrease the set temperature, press the
DOWN arrow key.
6. When the desired set temperature is shown,
release the UP or DOWN arrow key. The muffle
furnace automatically begins controlling to the
set temperature.
Ramp and Soak Mode
In Ramp and Soak mode of operation, the muffle furnace
executes a sequence of program commands. During a
ramp period, the muffle furnace temperature is controlled
to increase (or decrease) at a linear rate set by the opera-
tor. During a soak period, the furnace maintains a con-
stant temperature for a time interval selected by the oper-
ator.
10
Operation
Note
To rapidly increase or decrease the
set temperature, press and hold the
appropriate arrow key. To slowly
increment or decrement the set tem-
perature one degree at a time, press
and immediately release the arrow
key.

Program Steps
Aprogram consists of a sequence of operations or "steps"
which the muffle furnace is set up to perform. The pro-
grammed operations are executed in the order entered:
step 1, step 2, step 3, etc. A single program may have a
maximum of 24 steps, or as few as two (one must be an
End).
Program steps may be selected from among the four
basic operations described below. The corresponding dis-
play for each operation is shown at the left:
ASet Point (SP) program step causes the furnace set
temperature (shown in the Set Display) to be linearly
increased or decreased ("ramped") at a selected rate.
The Set Point operation begins at the current set tempera-
ture and finishes at the programmed Set Point tempera-
ture.
Soak causes the final set temperature from the preceding
step to be held for a time interval of up to 23 hours, 59
minutes and 59 seconds. This duration may be extended
by adding further Soak steps or using a Jump Loop (see
below).
AJump Loop operation causes program execution to
jump to another designated program step. Each program
step, up to the Jump Loop, is then sequentially repeated.
Use of a Jump Loop allows a programmed temperature
cycle to be repeated up to 100 times. A Jump Loop can-
not be used as the first step in a program.
Program execution proceeds sequentially through each
program step until an End is encountered, or until all 24
program steps have been completed. An End may be set
up to cause the furnace to maintain the final set tempera-
ture indefinitely or simply to turn off heater power.
If no End is used, all 24 program steps will be completed,
then the furnace will maintain the final programmed set
temperature.
11
OPERATION

Creating a Ramp and Soak
Program
Creating a program consists of constructing a sequence
of the four basic operations, Set Point (ramp), Soak,
Jump Loop and End, to produce a desired temperature
cycle. For each operation selected, several options
also must be specified. To enter a ramp and soak pro-
gram, perform the following procedures:
1. Verify the RUN LED is not lit. If it is, press the
RUN key until it goes out.
2. Press the MENU key. The No Program display
should appear (see left). If no key is pressed for
one minute, the display automatically reverts to
Control mode.
3. Press the UP-Arrow key once to present the
program entry menu selection.
4. Use the UP or DOWN Arrow key to select the
desired program number. Up to four programs
can be entered (Model 750 only).
5. Press the MENU key to initiate entry of the first
program number (Model 750 only), or when the
Actual display indicates YES (Model 650).
6. Press the UP or DOWN Arrow key until the
Actual Display shows the number of the step to
program. Press the MENU key to enter the
desired program step (1 to 24).
7. The Set Display then indicates 'StyP to signify
that the step type must be selected from a menu
of four operations being shown in the Actual
Display. The four menu selections are Set Point
(ramp), Soak, End or Jump Loop. These
menus appear as shown on the left. Repeatedly
press the UP or DOWN Arrow key until the
desired step type appears. NOTE: For step 1 in
a program, the jump loop option is not available.
8. If the desired program step is a ramp to a Set
Point, press the MENU key to select it when the
Actual Display reads "SP”. Otherwise, skip to
step 11.
12
OPERATION
Note
During programming, the MODE key
serves as an "enter" key to select a
value shown on the Actual Display
for a corresponding parameter
shown on the Set Display.
Note
Model 750 will prompt for program
number (1 to 4), while Model 650
prompts for single program entry
(Yes/No).
Model 650
Display
Model 750
Display

9. If a ramp to a Set Point is selected, the Set
Display first indicates "SP" to signify that the
operator must select a final target temperature,
or set point. Use the UP or DOWN Arrow key to
adjust the Actual Display to indicate the desired
final temperature for the ramp.
Press the MENU key to enter the selected set
point temperature.
10. The Set Display then indicates "rAtE" to prompt
the operator to select a desired heating or cool-
ing rate in °C/min or °F/min. Press and hold the
UP or DOWN Arrow key until the desired rate is
shown in the Actual Display.
Press the MENU key to enter the selected rate.
Proceed to step 21.
11. If the desired program step is a Soak, press the
MENU key to select it when the Actual Display
shows "'SoAh.". Otherwise, skip to step 15.
12. If a Soak is selected, the Set Display first indi-
cates "HOUr" to signify that the operator must
select the number of hours for which the current
set temperature will be maintained. Use the UP
or DOWN Arrow keys to adjust the Actual
Display to indicate the desired number of soak
hours (maximum of 23 hours).
Press the MENU key to enter the selected num-
ber of soak hours.
13. The Set Display then shows "Min" to indicate
that the operator must select the number of
additional minutes for which the current set tem-
perature will be held. Use the UP or DOWN
Arrow keys to set the Actual Display to the
desired number of soak minutes (maximum of
59).
Press MENU to enter the selected number of
soak minutes.
13
OPERATION

14. The Set Display then shows "SEC" to indicate
that the operator must select the number of
additional seconds for which the current set
temperature will be held. Use the UP or DOWN
Arrow key to adjust the Actual Display to indi-
cate the desired number of soak seconds (maxi-
mum of 59).
Press the MENU key to enter the selected num-
ber of soak seconds. Proceed to step 21.
15. If the desired program step is a Jump Loop,
press the MENU key to select it when the Actual
Display shows "JL.'" Otherwise, skip to step 18.
16. If a Jump Loop is selected, the Set Display first
indicates "JS" to signify that the operator must
select the step number destination for the jump.
Use the UP or DOWN Arrow key to adjust the
Actual Display to indicate the desired step num-
ber. NOTE: The jump step number must be
lower than the current step number. The
jump cannot be to the current step or a high-
er step.
Press the MENU key to enter the selected jump
step.
17. The Set Display then shows “JC” to indicate that
the operator must select the number of times
the jump loop is to be repeated. Use the UP or
DOWN Arrow key to adjust the Actual Display to
select the number of times the loop is to be
repeated.
Press the MENU key to enter the selected num-
ber of jump counts.
18. If the desired program step is an End, press the
MENU key to select it. Otherwise, skip to step
11.
19. If End is selected, the Set Display shows "End"
and the Actual Display shows one of the two
options for an End step. To view each selection,
repeatedly press either the UP or DOWN key.
The options appear as shown on the left.
14
OPERATION

20. If the final temperature is to be held indefinitely
at the end of the ramp and soak program, press
the MENU key when "HoLd" is displayed on the
Actual Display. If heater power is to be turned
off at the end of the program, press the MENU
key when the Actual Display indicates "OFF."
Proceed to step 21.
21. Once a program step is entered, the display
indicates “no rtn”. If further steps are to be pro-
grammed, press the MENU key to continue pro-
gramming. The next program step will be dis-
played. Return to step #6 of this procedure to
add more program steps. Up to 24 can be
entered per program. The Model 750 can
accommodate four 24 step programs.
22. If no further program steps are required, press
the UP Arrow key. The displays indicate “YES
rtn”. Press the MENU key to return to control
mode operation. To initiate the program, see
Running, Stopping or Resuming a Program.
Running, Stopping or Resuming
a Program
Prior to running the program in memory, first make certain
that the current set temperature is the temperature from
which the program is to start. For example, a program
intended to ramp the furnace temperature from ambient to
600 °C, if started with the current set temperature at
1000 °C, will actually ramp the temperature down from
1000 °C to 600 °C. Use the UP/DOWN arrow keys to
change the set temp if necessary.
To run the program currently in memory, perform the
following steps:
1. Press the RUN key once. The Run indicator
light begins to flash and the displays indicate the
first program number (Model 750) or the first
program step (Model 650). If running a program
from a Model 650, skip to step 3.
15
OPERATION

2. If running a program from a Model 750, use the
UP or DOWN arrow keys to cycle the Actual
display to the desired program number, 1
through 4, or NO to cancel. Use the MENU key
to select the desired program number to run.
3. The displays now indicate the first program step.
Program execution will begin at the current pro-
gram step. To change the program step use the
UP or DOWN arrow key until the desired step is
displayed. Press the RUN key to initiate the run,
beginning at the program step number shown.
Observe that the Run indicator comes on full
signifying that the furnace is in the ramp and
soak mode with a program underway.
To stop a running program, press the RUN key.
The RUN LED will turn off and furnace operation
returns to the Control mode, with the set tem-
perature at the last value achieved by the pro-
gram.
To resume program execution after stopping a
program, press the RUN key. The RUN LED
will begin to blink. Press the MENU key. The
displays indicate “x rESU”, where x is the last
executed program step. Press the RUN key
again. The program will continue executing at
the point it was stopped.
Viewing Program Status
While a ramp and soak program is running, the status of
the current program step may be viewed. With the Run
LED lit to indicate the program is running, successively
press the MENU key. Each control parameter associated
with the current program step then is displayed sequen-
tially. The parameter type is indicated in the Set Display,
while the value for the parameter appears in the Actual
Display. A final press of the MENU key returns the dis-
plays to tracking the actual and set temperatures.
The specific control parameters displayed in any instance
depend upon whether the current step is a Set Point or a
16
OPERATION
Model 750 Display

Soak operation. The sequence of control parameters dis-
played in each case, and the corresponding Set Display
messages (left), is as follows:
Set Point or Soak Step
End Set Point Target final temperature at the
completion of the ramp.
Rate Rate of change of temperature,
in °C/min, for the ramp.
Elapsed Jump Count
If a Jump Loop is in progress,
indicates the number of times
the loop has been executed.
Step Current program step.
Hour Hours remaining in the soak
step.
Min Minutes remaining in the soak
step.
Sec Seconds remaining in the soak
step.
An Example Program
The ASTM method for Ash Analysis of Coal and Coke (D
3174-89)1specifies the following ramp and soak opera-
tions:
Step 1: Ramp from ambient to 500 °C at 8.0 °C/min (i.e.,
in 1 hour)
Step 2: Ramp from 500 °C to 750 °C at 4.2 °C/min (i.e., in
1 hour)
Step 3: Soak at 750 °C for two hours
Step 4: Turn off power to the heaters and allow to cool
17
OPERATION
1American Society for Testing and Materials,
Gaseous Fuels: Coal and Coke, Vol.05.05,
Section 5, pp.326-8

To set up and run this program, perform the following pro-
cedures.
Programming Step 1:
1. With the Run LED off, press the RUN key.
Press the MENU key until the displays indicate
“no Prog”.
2. Press the UP arrow key. The displays will now
indicate “YES PrOg” (Model 650) or “1 PrOg”
(Model 750). Press the MENU key again.
3. The displays now show “1 StEP”. Press the
MENU key to begin programming at step #1.
4. Press the UP or DOWN arrow key until the dis-
plays indicate “SP StyP”. Press the MENU key
to select the set point ramping command. Alarm
5. Use the UP or DOWN arrow keys to display the
desired set point in the upper display (500°C).
When the displays indicate “500 SP” (500 set
point), press the MENU key to select the tem-
perature.
6. The controller will next prompt for the ramping
rate. Use the UP or DOWN arrow keys to enter
the desired ramping rate in degrees/min
(8.0°C/min). Press the MENU key to select the
ramping rate.
7. The first step is now programmed. The con-
troller will then display “no rEtn”. Press the
MENU key to remain in the program editing
mode. “2 StEP” is then displayed. Press the
MENU key to continue.
Programming Step 2:
8. Press the UP or DOWN arrow key until the dis-
plays indicate “SP StyP”. Press the MENU key
to select the second set point ramping com-
mand.
9. Use the UP or DOWN arrow keys to display the
desired set point in the upper display (750°C).
When the displays indicate “750 SP” (750 set
point), press the MENU key to select the tem-
perature.
18
OPERATION

10. The controller will next prompt for the ramping “rate”.
Use the UP or DOWN arrow keys to enter the
desired ramping rate in degrees/min (4.2°C/min).
Press the MENU key to select the ramping rate.
11. The controller will then display “no rEtn”. Press the
MENU key to remain in the program editing mode.
“3 StEP” is then displayed. Press the MENU key to
continue.
Programming Step 3
12. Press the UP or DOWN arrow key until the displays
indicate “SoAh StyP”. Press the MENU key to
select soak as the step type.
13. The displays will now show “0 Hour”. Use the UP or
DOWN arrow keys to display the desired soak time
in hours (2). Press the MENU key to select two
hours of soaking.
14. The controller will next prompt for the desired min-
utes of soaking “0 Min”. Press the MENU key to
select zero minutes.
15. The controller will next prompt for the desired sec-
onds of soaking “0 Sec”. Press the MENU key to
select zero seconds.
16. The total soak time is now programmed; 2 hrs, 0
minutes and 0 seconds. The controller will then dis-
play “no rEtn”. Press the MENU key to remain in
the program editing mode. “4 StEP” is then dis-
played. Press the MENU key to continue.
Programming Step 4
17. Press the UP or DOWN arrow key until the displays
indicate End StyP. Press the MENU key to select
the end command.
18. Press the Up arrow key until the displays show “oFF
End”. Press the MENU key to select.
19. Once and End statement is programmed, the con-
troller will prompt the user to save the current pro-
gram, “SAVE”. Press the MENU key to save the
program. The controller then returns to normal con-
trol mode.
Follow the procedures on page 15 to run the program.
19
OPERATION

High Temp Alarms
All Fisher Furnaces come equipped with high temperature
alarms. When an alarm condition occurs, power to the
heaters is removed while the Set display flashes between
the current set temperature and “HI”.
The high temperature alarm will activate when the actual
temperature is greater than the set temperature by more
than 25°C (45°F). The alarm condition will continue until
the actual temperature falls within 5°C (9°F) of the set
temperature.
Open Thermocouple
When the displays show “oPEn xx”, where “xx” desig-
nates the last set temperature, an open thermocouple is
being detected. Check the thermocouple connection and
replace if necessary.
Calibration
To calibrate the furnace, place a reference thermometer
or thermocouple lead inside the furnace chamber located
as close to the geometric center of the chamber as possi-
ble. Set the furnace to the desired temperature and allow
enough time for the temperature to stabilize.
Note the temperature as indicated by the reference ther-
mometer. Compare it to the temperature in the Actual
display. If the two readings do not agree, press the
MENU key twice. The displays should show “0 CAL”.
Use the UP or DOWN arrow key to adjust the calibration
(CAL) number to a value which will equal the temperature
of the reference thermometer when added to the most
recent temperature of the Actual display.
For Example: A furnace is set to 500°C and allowed to
stabilize. The reference thermometer indicates 505°C.
The furnace Actual display shows 500°C. The calibration
(CAL) value is set to +5 in order for the Actual display to
agree with the reference thermometer. Press the MENU
key four more times until the displays show the tempera-
tures with the Actual temperature corrected.
20
OPERATION
Caution
Use thermometers/thermocouples
suited for operation at temperatures
equal to or higher than the desired cali-
bration temperature.