RF detector power meter

[snkhan]

What is difference between RF-detector(Schottky diode detectors) and RF power meter.

RF detectors are cheaper so can they be used with voltmeter/oscilloscope as an alternative to power meter.

Thanks

 

[betwixt]

I'm not sure if you are asking a question or making a statement.

RF detectors are basically rectifiers designed for high frequencies, they tell you the voltage present at their inputs.

An RF power meter is a load resistor with an RF detector connected to it. In other words is measure the voltage across a load and by using Ohms law it is possible to calculate the power being dissipated in it.

Brian.

 

[snkhan]

Thanks

It mean both oscilloscope and voltmeter can be used with RF-detector to measure power.
Which one is better

 

[BigBoss]

Thanks

It mean both oscilloscope and voltmeter can be used with RF-detector to measure power.
Which one is better

Oscilloscopes don't measure power,instead they measure time domain waveform because their input impedances are generally high.But some of them have reasonable input impedances such as 50 Ohm, in this case the oscilloscope may measure the power but it's not the principal target of the oscilloscope.The same statement can be done for the Voltmeters.They have also very high input resistances and they are not used for power measurements.They have also insufficient bandwidth.
That's why Power Meters are used..

 

[Borber]

RF diode detector is not linear or Vdc/Vac is not constant but vary with input AC voltage amplitude. Thus linear DC voltmeter or oscilloscope is rather used as indicator if not calibrated in mW or dBm. When voltmeter is calibrated it shows correct power only for sine wave signal if calibrated using such signal. Measuring signals like square wave or clipped sine will show less than actual power is.

 

[snkhan]

I have old HP3582A (0.02Hz to 25.6KHz) spectrum analyzer. I will use with it and update the results

 

[jiripolivka]

I have old HP3582A (0.02Hz to 25.6KHz) spectrum analyzer. I will use with it and update the results

Best RF power meters utilize thermistors that are heated by input power and their resistance is calibrated against this input power.
Recently, many RF power meters utilize diode detectors that respond with output voltage as a function to input RF power to a matched resistor.
Both types are good after calibration.

Spectrum analyzers can measure RF input power if calibrated. Not all can be trusted as their frequency response is more important than measurng RF power.

 

[snkhan]

i started this post because i find many website selling RF-detectors@50GHz@300$. On the other hand all power meter are compatible with their own sensor dependent.

So i just wanna know that which device is to be used with Rf-detector to measure power

 

[jiripolivka]

Any device responding to RF power and well matched to line impedance can be used provided its response is calibrated.
Typical RF and microwave detectors are made for a high sensitivity, they respond to RF input from -30--40 dBm. But they are usually not well matched and diodes used are temperature dependent.

Diode RF power meters typically use a matching resistor and a pair of diodes connected to a differential DC amplifier. One diode senses RF power across the resistor, the other serves for temperature compensation. Such RF power meters often respond well to fast RF power changes while the "clasical" thermistor power meters do not.
Again, calibration is the secret.