Thursday, 3 March 2011

RF probe


RF  probes are  simple just  a diode, capacitor and  usually a resistor as well and  are  quite useful in homebrewing. The  output  from  the junction  of  the diode and capacitor is a DC voltage equal to  the peak voltage of  the signal applied But the usual way of  refemng to AC and RF  voltages is by the RMS  value, which is 0.707 times the  peak value. We could connect a voltmeter to this point and  read the peak value, then multiply by 0.707 but it's simpler to use the resistor. It  forms a voltage divider in  conjunction with  the input impedance of  the meter such that the output  is  approximately 0.707  of the peak,and thus the numbers on  the meter correspond directly to RMS witb no conversion needed.

No comments:

Post a Comment