* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download experiment_V
Galvanometer wikipedia , lookup
Transistor–transistor logic wikipedia , lookup
Standing wave ratio wikipedia , lookup
Radio transmitter design wikipedia , lookup
Spark-gap transmitter wikipedia , lookup
Oscilloscope history wikipedia , lookup
Integrating ADC wikipedia , lookup
Josephson voltage standard wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Schmitt trigger wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Electrical ballast wikipedia , lookup
Operational amplifier wikipedia , lookup
Power MOSFET wikipedia , lookup
Voltage regulator wikipedia , lookup
Power electronics wikipedia , lookup
Surge protector wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Opto-isolator wikipedia , lookup
Current mirror wikipedia , lookup
Lab #5: RC AC Circuits • remember how AC circuits containing capacitors and resistors behave. Caps and AC sources Voltage across cap is same as voltage across supply. When the voltage is changing quickly, the charge also has to change quickly -> big current V V0 sin( t ) 1 Q C Q CV0 sin( t ) dQ i CV0 cos( t ) CV0 sin( t / 2) dt i V0 sin( t ) 1/( C ) 2 V i0 (1/ C ) Size of the current depends on the frequency Get biggest currents at high frequencies AC RC Circuits As per last week, be careful with the grounds! • Presence of the capacitor affects the size of the current in the circuit in a frequency-dependent way. • “phases” of signals across voltage source, resistor, and capacitor differ • math is most easily done by modeling the voltage source as V V0eit instead of V V0 cos(t ) and an imaginary reactive for the capacitor (to shift its affect on the current by 90 degrees) and then taking the real part at the end. The Math What is the current? V0eit i (t ) Z i (t ) ( R 1 i ) i (t ) ( R ) iC C Any complex number can be written as a magnitude and an angle in the complex plane. Z R2 tan V0eit i (t ) R 1 1 i e 2 R 2C 2 V0 i (t ) R 1 1 2 R 2C 2 ei (t ) 1 1 R 1 2C 2 2 R 2C 2 1 RC Easy to read off mag of current. Current (and thus voltage across the resistor) is shifted in phase from the voltage source by V across R and across C Again, V across C tends to be large when V source is changing quickly hints • lab starts pg 47 • include syst errors for R and C measurements, but not for t and V measurements with scope. •MAKE SURE DUTY CYCLE IS ALL THE WAY COUNTER CLOCKWIZE! •pay attention to the scale (v/division) on ch1,ch2 VERY IMPORTANT WHEN DOING PART C!!! • phase shift can not be greater than pi • remember “compare” is a mathematical operation involving a chi^2 test • make sure the wave oscillates around zero (using the offset knob). Make sure there is no dc offset. • remember, VR lags VIN by phi • changes • use the 10k resistor and the 0.1mF cap for Part A. • in part A.1, where it says “between the zero crossings”, I suggest using the time between the maximums of the waveform instead. •For part A.1, capture your waveform and paste into lab report. • A-2. replace “qualitively” with “qualitively and quantitatively”. • In B, don’t go as low as 10 Hz. Do 50-500 Hz. • in part C, if your wave form is funny, your amplitude is too big for the instrumentation amplifier. Make it smaller Errors cos VR V0 2 2 VR V0 VR V0 1 VR from the first: sin and sin 2 VR V0 V0 V0 2 1 VR 1 VR 2 V0 sin V0 V0 2 2 1 1 cot( ) VR V0 VR V0 2 errors You measure dt. Calc y=cotan(2*pi*f*dt). What is error on y? y cot( ) 1 y 2 sin ( )