Daqarta
Data AcQuisition And RealTime Analysis
Scope  Spectrum  Spectrogram  Signal Generator
Software for Windows Science with your Sound Card! 

The following is from the Daqarta Help system:

Features:OscilloscopeSpectrum Analyzer 8Channel

Applications:Frequency responseDistortion measurementSpeech and musicMicrophone calibrationLoudspeaker testAuditory phenomenaMusical instrument tuningAnimal soundEvoked potentialsRotating machineryAutomotiveProduct testContact us about


Voltage DividersA simple 2resistor voltage divider can function as a fixed attenuator to reduce a signal level that is too large.
Given the input voltage Vi and the two resistors R1 and R2, the output voltage Vo is: Vo = Vi * R2 / (R1 + R2) The fractional voltage reduction K is: K = Vo / Vi = R2 / (R1 + R2) To get a specified output voltage from a known input voltage, pick one of the resistor values and solve for the other: R2 = Vo * R1 / (Vi  Vo) R1 = R2 * (Vi  Vo) / Vo Or, if you know the desired fraction K and want to find the resistors: R2 = K * R1 / (1  K) R1 = R2 * (1  K) / K The ratio of the two resistors needed for a given reduction is: R2/R1 = K / (1  K) R2/R1 = Vo / (Vi  Vo) To determine the input voltage that produces a given output voltage from a known divider: Vi = Vo * (R1 + R2) / R2 The reduction ratio K is normally used for range changes, such as 0.10 for a 10to1 reduction. However, for audio work you may want to obtain a specific reduction in dB. (See dB From Voltages and Working With dB.) The dB corresponding to a given voltage ratio is: dB = 20 * log10(Vo / Vi) dB = 20 * log10(K) where log is the base10 (common) logarithm. For voltage dividers, note that K is always less than 1, so the dB value will always be negative. To find the ratio K corresponding to a given dB value, use the following formula. Remember to use a negative value for dB: K = 10^(dB/20) Typical dB values and corresponding voltage ratios: 1 = 0.891251 2 = 0.794328 3 = 0.707946 6 = 0.501187 10 = 0.316228 20 = 0.100000 30 = 0.031623 40 = 0.010000 60 = 0.001000 80 = 0.000100 100 = 0.000010 120 = 0.000001 

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