Purpose Learn how to use basic electronic equipment: Digital multi meter Oscilloscope Function generator Bread board Apply and verify Ohm’s laws.

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) Note: We use the term “DC” or “AC” also for voltages, even though The “C” stands for “Current” (Example: 5V DC). You need to know whether you are measuring an “AC” or “DC” current/voltage and set your DMM accordingly. Otherwise your measurement is wrong.

AC Measuring AC with a DMM V or I time average value time If you measure this AC voltage/current in the “DC” mode, the result is the average (averaged over time) value (in this case zero). 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).  Always measure AC in the AC mode.

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

Setting AC or DC on DMM (Fluke 87) Current: Switch between DC and AC by pushing the blue button. DC voltage AC voltage

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

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. A very tiny amount of current (ideally almost zero) goes through the voltmeter. 5 V 0.003 current Resistor GND = 0 V V COM V Important: Use COM (ground) and V ports for voltage measurement!

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. 5 V current 0.003 Resistor A GND = 0 V mA COM V Important: Use COM (ground) and mA or A (large currents) ports for current measurement!

NEVER DO THIS !!!!!!!!!!!!!!!!!!!!!!!!!!! 5 V huge current 0.003 Resistor A GND = 0 V A COM V Fuse will blow out !!! 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.

The Correct Way, Again 5 V current 0.003 Resistor GND = 0 V Notice mA COM V 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).

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.

The Function Generator – Wave Shape Selection Sinusoidal Wave Square Wave Triangular (“Sawtooth”) Wave

The Function Generator – Frequency Range Within each range you can vary the frequency (see next slide). Up to 5 Hz Up to 50 Hz Up to 500 Hz

The Function Generator – Frequency Variation 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). Coarse regulation Fine regulation

The Function Generator – Output Level Adjust the amplitude of the signal at “Output Level”. Signal output: Connect BNC cable here.

What is “DC Offset” ? No “DC offset” 0 Volt Signal has “DC offset” of + 2 Volts (the signal fluctuates around +2 V instead of 0 V). 2 Volt 0 Volt

The Function Generator – Generating a “DC Offset” Push “DC OFFSET” Button IN to enable DC offset adjustments. Adjust the amount of DC offset here.

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.

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

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

How the “Holes” are NOT Connected Holes in a “row” are electrically NOT connected.

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.

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

Example of Setting up a Simple Circuit Circuit Diagram 5V Resistor 5 V GND A more pictorial view of the same circuit.

And How it Looks on the Bread Board

And from Another Angle….. Notice, how we take advantage of the hidden connections between the holes in a column.

Binary Numbers In digital electronics information is coded as binary numbers which contain only Ones and Zeroes. Example: 1001 (binary) = 1x23+0x22+0x21+1x20 = 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. 1 0 0 1 5V 0V 0V 5V

Data Switches, Logic Indicators The bread board has “Data Switches” providing “High” and “Low” voltage for digital logic . Switch Output (low or high) 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”). 0V (SW4 down) 5V (SW2 up)

Resistor Color Code Gold = 5% uncertainty First band Second band 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 W Resistance = 2 0 * 10 W = 200 W  10 W

The Oscilloscope Voltage time 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). Voltage time Channel 1 input Channel 2 input

Changing the Horizontal (Time) Scale Change horizontal time scale here.

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

Using the Cursor Press the CURSOR button to enable the cursors. Once the cursor button is pushed these two knobs move the two cursors.

Using the Cursor Change the type of cursor between voltage cursor or time cursor with this button. Indicates voltage difference between cursor 1 and 2. Indicates voltage at which cursors 1 and 2 are.

Time Cursor Selected The two time cursors.

Connectors and Their Names Center pin “BNC” cable “Shield” 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.

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.

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

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.

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.

Special Wires: Do not cut !

Banana Leads fit to DMM Ports Use COM and V ports for voltage and resistance measurements Black wire: COM (convention)

Microclips

BNC - Banana Adapter

Measuring Voltage with Microclips Completing a Circuit Measuring Voltage with Microclips

Measuring Current

Resistors in Series

Parallel Resistors - Measuring Current in Main Branch

Please put the special cables neatly back into the blue boxes !