To help in selecting
the most suitable equipment for your application, the operating characteristics
of our ovens and furnaces are shown on their product bulletins. This bulletin
more completely defines and explains these operating characteristics and
their use as a guideline for equipment selection.
have many different accuracy ratings for features such as set point,
display, repeatability and calibration. For the purpose of our product
bulletins, we have defined control accuracy as the ability of the
temperature controller to maintain a constant temperature, by altering
heat input, at the point in the equipment where the temperature is
being sensed. For this reason, we have chosen the manufacturer's
published accuracy rating of the temperature controller that would
most affect the stability of temperature at this sensing point.
Product bulletins for equipment using non-electronic temperature controllers
such as bi-metallic or fluid filled thermostats, list the control accuracy in
degrees. In these cases, the control accuracy gives an indication of the maximum
amount of cyclic variation which could be seen at the sensing point.
For electronic temperature controllers, the control accuracy on the product bulletins
is shown as a percent of the span and is a comparison of the temperature at the
sensing point to a calibration source. The span of the temperature controllers
is typically 900°F,
1600°F or 2400°F, depending on the maximum operating temperature of
most instances, the temperature fluctuation due to the electronic
temperature controller is dwarfed by the other
system characteristics affecting temperature uniformity such as loading,
exhaust rate and available
Equipment with heat input most closely sized to requirements will show the
least fluctuation at the sensing point. Very large heat input (most often
encountered in gas or steam heated equipment), can result in a large addition
of heat input to the system before the temperature controller can react. This
effect is minimized in gas and steam heated equipment by modulating the heat
input rather than turning it on and off. Electric ovens with large heat input
can minimize this effect by the installation of an SCR power controller. See
below for additional information.
Temperature controller accuracy is based on tests performed by the temperature
controller manufacturer with published results. This is only one of the many
specifications published by the temperature controller manufacturer. Complete
temperature controller specifications are available upon request.
uniformity is listed in degrees. This is a measurement of the
distribution of heat within the oven work space. This data is
the result of actual tests run in a stabilized empty oven with
a minimum of nine thermocoupleseight thermocouples located
at the corners of the work space and one in the center of the
work space. The corner thermocouples are placed 2" to 12" from
the work space edges (based on the size of the equipment) to
be representative of the usable work space. Temperature uniformity
will normally improve as the operating temperature is lowered.
Other factors may affect temperature uniformity adversely.
the air flow within the work space will adversely affect the
distribution of heated air and, therefore, the temperature uniformity.
Care must be taken to pick equipment with a recirculated air
flow pattern suited to the product loading.
uniformity tests have been run with minimal exhaust from the equipment.
Heat input that is required to offset a large exhaust rate can
be compensated for by increasing heat input. However, a large exhaust
rate can have a detrimental effect on temperature uniformity. Hot
air exhausted must be replaced with cooler fresh air. The fresh
air is heated by being recirculated through the heat source. The
larger the exhaust rate, the less the fresh air is mixed before
being exhausted. This will result in non-uniform temperatures in
the recirculated air flow.
If tight temperature uniformity is required with a large exhaust rate, it may
be necessary to increase the size of the recirculating blower in the equipment.
Those applications which will require large exhaust rates should be discussed
with our sales engineers. In furnaces, where the heat transfer is by radiant
heat, high temperature fans can be added to the equipment or the heating elements
zoned within the work space to improve temperature uniformity. These applications
should be discussed with a factory sales engineer.
The time required
to heat oven air to set point (rise time) is a measure of available
heat input and an indication of how fast an oven may heat up. The
rise time information is based on actual tests measuring the time
required for temperature at the sensing point to rise from room
temperature to set point.
The rise time tests were run with an empty oven and a minimum exhaust rate. Lower
than design voltage on electric equipment or insufficient gas pressure on gas
equipment will reduce heat input and increase rise time. Increased exhaust or
heavy loads will also increase the time required to rise to set temperature.
is necessary to heat up internal steel and insulation that surrounds
the work space. Once the equipment reaches the set temperature,
additional time is required to stabilize temperatures within the
oven. During this stabilization period, the insulation is heated
and the temperature profile through the insulated wall will reach
a steady state. As this happens, the output of the heat source will
reduce from maximum to the much smaller amount required to offset
the loss through the insulated walls and exhaust.
While both a high exhaust rate and a large load will increase the time to reach
set point and stabilize, only the exhaust rate will increase power consumption
after stabilization. Once the load is stabilized, the power consumption will
be the same as for an unloaded oven.
have provided addition details on our standard digital
temperature controller as well as details on the optional controllers
listed on our Product Bulletins. Other brands or models of instruments
are also available contact one of our sales engineers.
have been selected to provide a full range of features at an economical
price. Consideration has also been given to selecting instruments
that are easy to understand and use.
We can provide
full installation and configuration of any other instrument. Also,
alternate control arrangements such as remote or free standing control
panels are available. Please contact our sales engineers in your
DIGITAL TEMPERATURE CONTROLLER
Display, two LED, alphanumeric,
four digit displays; 0.875" high for temperature
display and 0.500" high for set point display
of span plus one degree display error
EXCESS TEMPERATURE INTERLOCK
Display, two LED, alphanumeric,
four digit displays; 0.425" high for temperature
display and 0.275" high for set point display
of span plus one degree display error
Parameters, 40 profiles of up to 50 steps each, a real-time clock with battery backup to allow starting profile at any time of day
Display, 4.3” color touch screen
Accuracy, ±0.1% of span plus 1 degree display error
Connectivity, Relay output for alarm or other notification, two (2)
USB ports, Ethernet compatable
Up to four (4) control channels of temperature, relative humidity
Display, 0.56" high, LED, alphanumeric, 4 digit
display; LED status display
of reading plus 1 degree display error
controlled rectifier power controllers are completely
solid state industrial controllers that insure precise
proportioning of electric power to the heating elements.
Oven temperature is maintained smoothly and evenly over
the entire temperature range of the unit. SCR power controllers
minimize maintenance, as there are no moving parts or
electrical contacts to wear out. Heating element fatigue
is reduced since the elements do not cool between releases
of electric power. Zero voltage firing, including the
first one half cycle of voltage, minimizes radio frequency
and electromagnetic interference. Transient voltage suppresser
networks are included and the units are provided with