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Formula

Ohm’s law
I=U/R
Joule's law:
Q=I²Rt
Q=UIt=Pt=UQ电量=U²t/R
Series circuit :
I=I1=I2
U=U1+U2
R=R1+R2
U1/U2=R1/R2
P1/P2=R1/R2
Parallel circuit:
I=I1+I2
U=U1=U2
1/R=1/R1+1/R2 [ R=R1R2/(R1+R2)]
I1/I2=R2/R1
P1/P2=R2/R1
Resistance
I1/I2=U1/U2
P1/P2=I12/I22
P1/P2=U12/U22
Electric Power
W=UIt=Pt=UQ
W=Iˆ2Rt=Uˆ2t/R
Watt:
P=W/t=UI
P=Iˆ2R=Uˆ2/R

 

Glossary

Etched-foil: A method of producing pre-determined electrical paths,by chemically removing(etching)the areas which will not carry electric current.This process can be used to manufacture heaters,flex-circuits,and temperature sensors.

Mica: A fairly brittle phyllosilicate mineral used to insulate heaters. It is used primarily for its high temperature and high watt density capabilities.

Polyimide: A flexible, amber-colored, translucent film to electrically insulate heaters, flex circuits, and Thermal-Ribbons. It is widely used for its temperature range and resistance to chemicals.

Resistance density: Resistance per unit area. Usually listed as a maximum, it is dependent upon construction materials such as foil, adhensive, and insulation.

Watt density:The amount of power per uint area,often expressed as watts per square inch or watts per square centimerters.

Silicone rubber: A flexible,synthetic elastomer used to electically insulate heaters and Thermal-Ribbons.

Vulcanize: A process,using heat and pressure,used to bond uncured rubber to rubber,metal,ceramic,glass.etc.

Insulation resistance:The actual resistance of an electrically insulating material.Measuring devices typically use high DC voltage to perform the measurement.

AWG(American Wire Gauge):An indicator of wire diameter.The larger the number,the smaller the diameter.

Conduction:The transfer of thermal energy between adjacent bodies(usually solids)or parts of the same body.

Flex circuit:A printed circuit made with flexible materials for compact electrical interconnects.

Resistance tolerance: The range of actual resistance from nominal(or target resistance),at a reference temperature(usually 0℃).Generally,wire elements have a tighter resistance tolerance than etched foil elements.


Specific heat:The amount of heat per unit mass required to raise the temperature of a material 1℃.

Watt: The heat produced by one ampere of current through a resistive load of one ohm.

 

Frequently Asked Question:

What is the correct voltage for this heater?
Standard heaters are specified by resistance,not voltage.This lets you operatethem at different power levels, In selecting a heater model you should consider the size, ℃att density depends on the insulation type,mount-ing method and operating temperature. Graphs of these limits are included in each product section of this bulletin.

Can I immerse these heaters in water or other liquids?
Generally the answer is no. The material used in polyimide insulated thermofoil heaters are waterproof, but edges are not sufficiently sealed for immersion.custom designs(including all PTFE heaters) can include increased border areas and sealed leadwire connections that make these heaters immersible in water. Silicone rubber insulated heaters require RTV cement or similar materials along all exposed edges and leadwire attachment areas for immersion in water.
If your application requires contact with other liquids contact. 


Can a heater be used suspended in air?
Because the mass of a heater is very small they are generally not suitable for heating in air. The heaters operate best when mounted to an object that can be heated by conduction rather than convection or radiation.


What is the dielectric strength of each different insulation material?
The heaters with polyimide,silicone rubber or mica insulation are test to verify 1000 VAC minimum dielectric breakdown voltage. We can provide custom models with thicker insulation to increase thedieletric rating,but this will reduce the maximum power and temperature rating for the heater.

Another consideration is the amount of dielectric leakage current at operating voltage.Because an etched element covers 50% or more of the heater surface area,it can acts as capacitor when AC power is applied. The result is a leakage due to capacitive effect. This is not failure of insulation but it may exceed the very low limits required for some medical and other applications .


Can I trim a heater to the size and shape I need after I have received it?
No, the heaters cannot be cut or trimmed. The element conductor covers the entire area to maximize the heat spreading effect of etched-foil design.Cutting into this would create an electrically open circuit and expose the electrically live element.

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