Frequently Asked Questions
- What is the principle of radiation in your emitters?
In Intex emitters, a thin conductive film is heated by the electric current. The spectrum is that of thermal black body radiation (Planck's Equation) with an emissivity of approximately 0.8.
- What are the main advantages of such sources?
Intex emitters radiate a wide spectrum and have a relatively fast response time. They can be used as a source of pulsed radiation up to 100 Hz without a mechanical modulator.
- What forms of voltage may be used?
There are no restrictions on the waveforms and polarities of applied voltage.
- What is the maximum temperature of the radiator?
The emitter survives short excursions up to 900 °C. But we recommend 750 °C and guarantee an emitter life of 100,000 hours at 605 °C with rectangular voltage pulses and a duty cycle of 50%.
- How can I determine the temperature for another voltage or power setting?
If another temperature is desired, it can be estimated from the graphs below. P/Pnom is the ratio of desired power to nominal power; the power coefficient. V/Vnom is the ratio of desired voltage to nominal voltage.
For short pulses and duty cycle 50% you can determine the power coefficient from the above graph and correct for power. Also, for voltage pulses where t < 50 ms, you can adjust the voltage and power experimentally. For this, you must use a fast-response (0.5 ms or less) detector to measure the emitter temperature. Perform the initial calibration of your detector with nominal-voltage pulses. The measured amplitude of the output signal corresponds to a temperature of 750ºC. Power the emitter with the required form and frequency and adjust voltage to give the same amplitude signal as during calibration. The required voltage for another temperature can then be estimated from these same graphs.
For voltage pulses where t > 50 ms, the emitters reach a stable temperature and in this case, nominal parameters are indicated in the specification.
- What is the main parameter to adjust the power source; nominal voltage or nominal current?
You may use both nominal voltage and nominal current, but the best way is to adjust the overall nominal power. Emitter temperature and radiation are dependent on the power.
- What is the dependence of emitter lifetime on temperature and duty cycle?
Higher operating temperatures translate to shorter device lifetimes. Lifetime may be estimated from the graph below.
- Can Intex emitters operate in vacuum?
Yes. But the nominal parameters in vacuum will be changed. The emitter temperature results from the balance between input power and energy dissipation. Approximately 60% of the heat energy is dissipated in air, about 24% to the silicon frame and only about 16% is radiated. Operation in vacuum cuts power consumption by more than 2X, however the cooling response time will increase proportionally and the heating response time will decrease as well.
- You mention response time. What is it and how is it measured?
The response time is the time for the IR signal, as measured by a detector, to drop to 50% of its maximum amplitude. We use an InSb detector (response time = 0.1 ms) for IR radiation (λ ~ 3 μ). It is measured upon cooling in the following way:
Nominal voltage and power are applied to the emitter with 100 ms rectangular pulses and 50% duty cycle. When the emitter is switched off, the time is measured for the temperature to decrease to from 750°C to 630°C which decreases the radiation to ½ of its nominal power value. This is illustrated in the following graphs.
One hundred milliseconds is enough time for the membrane to achieve a steady-state temperature upon heating and cooling and signal amplitude does not depend on response time. This measurement of response time allows comparison of emitter performance.
- Does the radiation depend on ambient temperature?
The radiation depends on the temperature of the emitter. For a given input power, changes of ambient temperature cause the same change in emitter temperature. The result can be estimated, as radiation is proportional to T4. For example, an increase of 10°C in ambient temperature increases the radiation by about 4%. For stable radiation, the emitter temperature must be stable.
- What must the temperature of header be for its normal operation?
Nominal parameters are specified for emitters without a heat sink at a standard ambient temperature of 60°C. The temperature can be stabilized however up to 100°C. You can estimate the correction of the input power as follows: every 10°C increase in case temperature allows for lowering of input power by 2.3%.
- Must the emitters be visually inspected and cleaned prior to installation? If yes, what is the recommended cleaning procedure?
It is not recommended to clean emitters before use as they are fragile..
Typical waveform applied to emitters
- a = Pulse voltage
- b = One period
- c = Pulse duration
- c/b = Duty cycle
Power Coefficient - Ratio of required applied power to nominal power. It is necessary to multiply nominal power by this number when using pulse durations of 50 ms or less.
Pulsed Broadband Infrared Light Source INTX 17 0900
Intex has developed a series of unique high-intensity pulsed infrared (IR) light sources capable of operating at high frequencies. Modulation of the light output is achieved by modulating the input electrical power, eliminating moving parts. The emission spectrum is that of a black body.