Instru Test 2 Part 2

Low Pass filter shape

High pass filter shape

Band pass filter shape

Band-stop (low-high-pass) filter shape

Show the pass band and stop band on the given filter shown in the following figure. Estimate the cutoff frequency(s)

Passband = 800 - 200 = 600 Hz

Stop Band = 2*(200) = 400 Hz

An inverting op-amp circuit has a gain of 28 dB and is to output a nominal signal voltage of -1.25 V. If the circuit measures to be 2.5 mA across R2, what is the value of the resistors (R1 and R2) used in the circuit.

Draw an inverting op amp filter

10. Suppose this is connected to a sensor with an output impedance of 10 Ω, would you expect this inverting circuit to cause significant loading errors?

Sensor output voltage is the same as filter input voltage:

So, do voltage divider where we are interested in the voltage across R1 considering the impedance of the sensor:

Vin’ = Vsensor x R1/(R1+Zsensor)

Vin’ = 19.9/29.9 x Vsensor = 0.665Vsensor     I think this means there would be a 33.5% loading error.

 If a 741 Op-amp (with GBP = 1 MHz) is used, what will the cutoff frequency of the amplifier circuit be? This uses Gain from question 8 as 25.12

GBP=bandwidth*Gain at which the bandwidth is measured

F_c=GBP/Gain

GBP= 1MHz

Gain for the op amp=25.12

F_c= 39.8 kHz ???????

A low-pass Butterworth filter has a passband gain of 0dB, a cutoff frequency of 10 kHz, and a roll-off of 6 dB/octave in the stopband. What will the voltage gain be at 40 kHz in dB?

Gain at 40kHz = 2* -6= -12

A 3 V signal is amplified to 30 V through a non-inverting amplifier circuit. If R1 is measured to be 4.7 kΩ, what is R2?
and draw the circuit

6 major elements of a useful instrumentation

Measureand - sensor - signal conditioning - DAQ - record/display - interpret

3 reasons why you might want to filter a signal

get rid of noise, avoid aliasing, if you only want data from a certain range of frequencies

advantage of butterworth

maximally flat passband

advantage of bessel

nearly linear variation of phase angle with frequency in the passband. linear/flat phase angle response so all freq delayed by same amount of time

advantage of chebyshev

crisper change in slope

how to convert gain from magnitude to dB

20log(gain)

4 general types of filters

lowpass, highpass, passband, stopband

bessel

blue

butterworth

red

chebyshev

black

what type of circuit is typically used to achieve voltage attenuation

op amps

octave is ______ the frequency

double

what does CMRR stand for

Common Mode Rejection Ratio

disadvantage of butterworth

does not have a crisp change in slope

disadvantage of bessel

lower roll-off rate

disadvantage of chebyshev

ripple in passband gain