Physics 2225: Working With Electronic Equipment Purpose  Learn how to use basic electronic equipment: Digital multi meter Oscilloscope Function generator Bread board  Apply and verify Ohm’s laws.

Physics 2225: Working With Electronic Equipment Digital Multi Meter (“DMM”) A DMM is a device to measure voltage, current, resistance, and more….depending on the model There are two modes to measure voltage and current: “AC” (alternating current) “DC” (direct current) You need to know whether you are measuring an “AC” or “DC” current/voltage and set your DMM accordingly. Otherwise your measurement is wrong. Note: We use the term “DC” or “AC” also for voltages, even though The “C” stands for “Current” (Example: 5V DC).

Physics 2225: Working With Electronic Equipment Measuring AC with a DMM V or I time AC If you measure this AC voltage/current in the “DC” mode, the result is the average (averaged over time) value (in this case zero). average value If you measure this AC voltage/current in the “AC” mode, the result is the the peak value divided by (assuming a sinusoidal oscillation around zero). A  Always measure AC in the AC mode.

Physics 2225: Working With Electronic Equipment Measuring DC with a DMM V or I time DC If you measure this voltage/current in the “DC” mode, the result is the average (averaged over time) value, which equals the DC value. average value  Always measure DC in the DC mode.

Physics 2225: Working With Electronic Equipment Setting AC or DC on DMM (Fluke 87) DC voltage AC voltage Current: Switch between DC and AC by pushing the blue button.

Physics 2225: Working With Electronic Equipment Setting AC or DC on DMM (MultiTec 320) Voltage: Put dial to “V”. Switch between DC and AC by pushing the DC/AC button. Current: Put dial to mA or A. Switch between DC and AC by pushing the DC/AC button.

Physics 2225: Working With Electronic Equipment Measuring a Voltage with the DMM Voltmeters have very high resistance.  Very little current will flow through a voltmeter even if V is high.  It is hard to damage a voltmeter. Voltmeters are connected “in parallel” to measure the voltage between two points COM V V Resistor 5 V GND = 0 V current A very tiny amount of current (ideally almost zero) goes through the voltmeter. Important: Use COM (ground) and V ports for voltage measurement!

Physics 2225: Working With Electronic Equipment Measuring a Current with the DMM Current meters (“amp meters”) have very low resistance.  When hooked up to an even small voltage difference, a large current would flow through a current meter.  It would be easy to damage a current meter.  Current meters are protected by a fuse (if you blow the fuse the current meter will no longer work until the fuse is replaced). Amp meters are connected “in series” to measure the current in a circuit COM V A Resistor 5 V GND = 0 V current Important: Use COM (ground) and mA or A (large currents) ports for current measurement! mA

Physics 2225: Working With Electronic Equipment NEVER DO THIS !!!!!!!!!!!!!!!!!!!!!!!!!!! COM V A Resistor 5 V GND = 0 V huge current Because the amp meter has almost no resistance, it gives the electrons an easy path between 5V and ground.  Huge current through amp meter will blow the fuse. A Fuse will blow out !!!

Physics 2225: Working With Electronic Equipment The Correct Way, Again COM V A Resistor 5 V GND = 0 V current Notice If you follow the path of the current you can see that it is forced to go through the resistor, which limits its current (by Ohm’s law….Current = Voltage / Resistance). mA

Physics 2225: Working With Electronic Equipment The Function Generator Time-varying voltage/current. Three different wave shapes (sinusoidal, square, triangular). Variable frequency. Variable amplitude of the signal. DC offset of signal.

Physics 2225: Working With Electronic Equipment The Function Generator – Wave Shape Selection Sinusoidal Wave Square Wave Triangular (“Sawtooth”) Wave

Physics 2225: Working With Electronic Equipment The Function Generator – Frequency Range Up to 5 Hz Up to 50 Hz Up to 500 Hz Within each range you can vary the frequency (see next slide).

Physics 2225: Working With Electronic Equipment The Function Generator – Frequency Variation Coarse regulation Fine regulation Display of frequency: For low frequencies you need to wait a few seconds for the correct value to show (it takes time to measure it).

Physics 2225: Working With Electronic Equipment The Function Generator – Output Level Signal output: Connect BNC cable here. Adjust the amplitude of the signal at “Output Level”.

Physics 2225: Working With Electronic Equipment What is “DC Offset” ? 0 Volt No “DC offset” 0 Volt 2 Volt Signal has “DC offset” of + 2 Volts (the signal fluctuates around +2 V instead of 0 V).

Physics 2225: Working With Electronic Equipment The Function Generator – Generating a “DC Offset” Push “DC OFFSET” Button IN to enable DC offset adjustments. Adjust the amount of DC offset here.

Physics 2225: Working With Electronic Equipment The Heathkit “Bread Board” Called “Bread Board” because you can use it to “breed” electric circuits. The board allows you to test your circuits before you build a permanent version.

Physics 2225: Working With Electronic Equipment The Heathkit “Bread Board” – the Actual “Board” This is the board: Makes connecting electric components (resistors, capacitors, integrated circuits…) EASY.

Physics 2225: Working With Electronic Equipment How the “Holes” are Connected 5 holes in a “column” are electrically connected. But: Red and Green are NOT connected across the center break. The center break

Physics 2225: Working With Electronic Equipment How the “Holes” are NOT Connected Holes in a “row” are electrically NOT connected.

Physics 2225: Working With Electronic Equipment How the “Holes” are NOT Connected Top break Holes are NOT connected across the top break. Note: Many of our bread boards do not have the double row above the top break any more.

Physics 2225: Working With Electronic Equipment Power Supply to the Bread Board Main Power: Switches all voltages ON or OFF. GND = 0 Volts (“Ground”) Example: To get 5 Volts: Use GND and +5

Physics 2225: Working With Electronic Equipment Example of Setting up a Simple Circuit Resistor 5 V GND 5V R Circuit Diagram A more pictorial view of the same circuit.

Physics 2225: Working With Electronic Equipment And How it Looks on the Bread Board

Physics 2225: Working With Electronic Equipment And from Another Angle….. Notice, how we take advantage of the hidden connections between the holes in a column.

Physics 2225: Working With Electronic Equipment Binary Numbers In digital electronics information is coded as binary numbers which contain only Ones and Zeroes. Example: 1001 (binary) = 1x2 3 +0x2 2 +0x2 1 +1x2 0 = 9 (decimal) Any decimal number can be converted to a binary number and stored electronically (e.g., in a computer). 1’s and 0’s are often stored as High (5Volt) and Low (0 Volt) voltages. For example, the number shown above (1001) could be represented by 4 “data lines” that have either high or low voltages. 5V 0V

Physics 2225: Working With Electronic Equipment Data Switches, Logic Indicators The bread board has “Data Switches” providing “High” and “Low” voltage for digital logic. The bread board also has LEDs (Light Emitting Diodes) which act as logic indicators (a quick way to find out whether a voltage is “High” or “Low”). Switch Output (low or high) 5V (SW2 up) 0V (SW4 down)

Physics 2225: Working With Electronic Equipment Resistor Color Code Our resistors have 4 colored bands on them. See your manual for color code. Gold = 5% uncertainty First band Red = 2 Second band Black = 0 Third band Brown = Multiplier 10  Resistance = 2 0 * 10  = 200  10 

Physics 2225: Working With Electronic Equipment The Oscilloscope A device to display a voltage as a function of time (useful for voltages that vary with time – e.g. oscillating signals). You can display 2 signals simultaneously using the two input channels (Ch.1 and 2). time Voltage Channel 1 input Channel 2 input

Physics 2225: Working With Electronic Equipment Changing the Horizontal (Time) Scale Change horizontal time scale here.

Physics 2225: Working With Electronic Equipment Changing the Vertical Scale on Channel 1 Change the vertical scale here. For more options on how to use channel 1 press the MENU button. The little knob shifts the signal up or down (unless the cursor is used).

Physics 2225: Working With Electronic Equipment Using the Cursor Press the CURSOR button to enable the cursors. Once the cursor button is pushed these two knobs move the two cursors.

Physics 2225: Working With Electronic Equipment Using the Cursor Change the type of cursor between voltage cursor or time cursor with this button. Indicates voltage at which cursors 1 and 2 are. Indicates voltage difference between cursor 1 and 2.

Physics 2225: Working With Electronic Equipment Time Cursor Selected The two time cursors.

Physics 2225: Working With Electronic Equipment Connectors and Their Names “BNC” cable “Shield” Center pin A BNC cable is basically a double cable: One “cable” is the center conductor ending in the center pin. The other “cable” is the “shield”.  A BNC cable can do the job of two parallel wires.

Physics 2225: Working With Electronic Equipment An Adaptor Used in this Lab Adapter: BNC (female) to Banana (male) “Ground” indicator: Indicates that this side of the banana end connects to the “Shield” of the BNC connector. The other banana end connects to the center conductor of the BNC.

Physics 2225: Working With Electronic Equipment Suggestion for Using Cables and DMM BNC small clips easily attach to resistors etc. Use adapter to plug into DMM The “Ground” plug on the BNC/Banana adapter connects to the small black clip.

Physics 2225: Working With Electronic Equipment More….. More and different types of cables can be throughout room 405 hanging on the walls. There are also more and other types of adapters in the brown cabinet labeled “L” to the left of the entrance or they may be on the shared table. Should – against all warnings – you blow a fuse on your DMM, ask your TA for a replacement.

Physics 2225: Working With Electronic Equipment Checking Fuse on Mutitec320 DMM is Easy Just dial to “mA” and the display should look like this. This symbol indicates a broken fuse. Other types of DMMs have no indicator.