Digital Multimeter: This handheld device is used by this course to measure voltage and resistance we will not use this to measure current or capacitan

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7 Digital Multimeter: This handheld device is used by this course to measure voltage and resistance we will not use this to measure current or capacitance. For current you will use an analog ammeter and for capacitance you will use a separate LCR meter. A R V C A COM V, black red

8 a) For the labs in this class you will be using DC (Direct Current) circuits, so make sure the meters are switched to DC mode. b) The Red probe goes in the red hole on the bottom right labeled (V,Ω) and the black probe goes into the next hole labeled com. In the voltage mode, the meter reads the potential of the red probe relative to the black probe. c) The values indicated on the settings are the maximum measurable values for this setting, if you get an OL response, it means you are out of range and you need to use a higher setting. Typically you want to use the lowest permissible setting to get the maximum precision for the instrument. d) In many of these DMM s, the lowest resistance setting also beeps indicating there is continuity, sometimes a useful piece of information, but the beeping can sometimes be irritating. e) To measure low resistances, you must touch the ends of the probes together to measure the internal: resistance this must be subtracted off any measured small resistance to take the internal resistance into account.

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14 Power Supply: The power supply delivers current as a result of applied voltage, a properly working supply will show a green light. If the light turns red, you will have to increase the current setting. Power = current x voltage. The Red output = positive (+) terminal The Black output = negative (-) terminal The Green output = ground The current and voltage settings have a coarse and fine control current voltage F C F C on/off - + B G R

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16 Proper operation: i) turn all the dials to zero initially, then ii) adjust the coarse CURRENT setting about half maximum, then iii) adjust the voltage to the desired current or voltage value. You can increase voltage until you reach your pre-set current value (P = I x V), to get more voltage (or more power) you will have to increase the current setting

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18 3. Breadboard Many times you will be assembling components together on a breadboard. This is a device specifically designed for plugging components together WE WILL NOT BE TWISTING WIRES TOGETHER!! There are several rows of holes. Each group of 5 holes are connected together with a copper strip, thereby creating a conductive path between the 5 holes.

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22 To ensure the components are connected together, make sure the connected components lie in the same column of 5 holes. The red and black banana connectors on the side are not connected to anything on the breadboard turn the breadboard upside down and you will see. If you want to attach power there, you need to also attach jumper wires from the banana plugs to the breadboard or just connect directly to the breadboard. Jumper wires (short insulated wires that are stripped at the ends) can also be used to connect components from one part of the breadboard to other parts. When components are assembled on the breadboard, you cannot directly measure the value of that component (resistor or capacitor) as your measurement will measure the equivalent value between the two probes in all cases. obviously there will be some times that such a measurement is OK, but in most cases it is not so don t start bad habits!

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24 Exercise: Using the DMM, set to measure up to 4.00 volts, put the red probe in the red output and the black probe in the black output. Using the technique above for proper operation,set the voltage to show 4.00 volts on the DMM the meter should show (+) 4.00 and the conventional current is flowing from Red-to-Black between the probes. If you reverse the probes, red probe in the black output and black probe in the red output, the meter should show (- 4.00). So when properly set up, the voltage sign will tell you which way the conventional current is flowing positive potential difference means conventional current flows between the probes, Red-to-Black. Series and Parallel: series R1 R2 current parallel R1 R2

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27 a) In series, both resistors should have the same current and their voltages add together. b) In parallel, both resistors have the same voltage drop and the incoming current divides between the two such that the voltages are equal. i current R1 R2 i1 i2 Such that V1 = V2 = i1 R1 = i2 R2 c) Verify these two conditions

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32 For series: 1. Apply 4.00 volts to the series combination 2. Measure: V1 = V2 = V1+V2 = Using the ammeter, measure first incoming current: i = Then measure i1 = i2 = Predict i1 and i2: I = V/R, i1 = V1/R1 and i2 = V2/R2 i1 = i2 =, the two sets of values should be equal

33 A i R1 R2 current R1 i1 A R2 R1 R2 i2 A

34 3. For the parallel combination:, again apply the 4.00 volts. 4. Measure: V1 = V2 = Using the ammeter, measure first incoming current: i =

35 i R1 A R2 R1 i1 A R2 R1 R2 A i2 Then reconnect the ammeter as shown and measure: i1 = i2 =, sum the two: i1+i2 = and the sum should equal i from above (or at least be close, since the ammeters provide a little resistance to the circuit.

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