Bin Contents: 2 Digital Multi Meters (DMM), a pack of Wires (center), an equivalent resistance box (top) and three resistors (bottom).

NOTE: Be careful with the wires! Never pull by from the cord! Always pull from the plug!

Also – re-tie the wires as indicated! 

Obtain a Gray and a Black LVPS (Low Voltage Power Supply) – return when finished.

NOTE: The Black LVPS is only used for Part D!

For Part A, you need to measure the resistance of each resistor – AND:

… and the combined series resistance for R1 and R2 (the picture is erroneously using R3, nevertheless, this is how R1 and R2 would be connected in series!)

The LCR meter connected to the two resistors in series.

Resistors in series generate a larger resistance than either.

NOTE: You may also use your DMM set to Ohm instead of the LCR.

… and the combined parallel resistance for R1 and R2 (the picture is erroneously using R3, nevertheless, this is how R1 and R2 would be connected in parallel!)

The LCR meter connected to the two resistors in parallel.

Resistors in parallel generate a smaller resistance than either.

NOTE: You may also use your DMM set to Ohm instead of the LCR.

Two resistors in series connected to the GRAY LVPS for Part B.

And here we are measuring the voltage for the resistor on the left.

This is how you take the voltage for both resistors simultaneously.

This is how you take the voltage coming out of the Gray LVPS.

To measure the current, remove the volt meter so that we aren’t cluttered by its wires, then produce a “hole” in the circuit simply a pulling a wire, then connect the current meter into that “hole” to fill it. In this image we made a hole by pulling the black wire out of the LVPS’s – port; the DMM was connected into that hole with the proper polarity indicated.

The same idea applies to measuring the current anywhere else along the circuit. For this image a hole was made by pulling the wire between the resistor and filling it with the DMM.

Again the same idea is used to measure the current at this location; here the red wire was pulled from the right-most resistor and the hole was filled by the DMM.

When you are finished measuring the voltage and current for the different components of the Part B circuit, remove the entire circuit from the Gray LVPS and replace with the equivalent resistance box; hook this box up directly to the LVPS. Use the results of your Part A measurement for the resistance of R1 and R2 in series, ROUNDED to the next whole number, and dial it into the top row of the box.

NOTE: none of your resistances for Part A will ever approach even 1k-Ohm, therefore, only the top row of dials need to be adjusted; the bottom row should be set to zero.

If your series resistance measurement for R1 and R2 was 355.8 ohm, round to the next whole number, 356, and set the dial so that the 1-Ohm is at 6, the 10-Ohm is at 5 and the 100-Ohm is at 3 – see how the digits become the settings of the dials?

Once this is setup, simply measure the voltage across the red and black leads as well as the current passing through the box and move onto Part C.

Two resistors in parallel connected to the GRAY LVPS for Part C.

As was the case for Part B, measure voltages first, currents last. Here we are measuring the voltage across the resistor on the right.

Here we are measuring voltage for the resistor on the left.

Here we measure the voltage for the LVPS itself.

The rules to measure current are exactly the same for Part C as they were for Part B. Always “break” the circuit by making a “hole” where you want to measure current through. In this case we are measuring the current that travels back into the LVPS.

To measure the current through the right resistor, simply remove one of the two leads that connect it to the circuit; it doesn’t matter which but for consistency we always chose the black lead.

Fill the hole by connecting the current meter to the resistor and to the lead that you removed.

Exactly the same idea applies for the left resistor; create a hole by removing one of the leads that connects it to the circuit.

Then fill that hole by connecting the current meter in series with the resistor and the lead that was removed.

When you are finished measuring the voltage and current for the different components of the Part C circuit, remove the entire circuit from the Gray LVPS and replace with the equivalent resistance box; hook this box up directly to the LVPS. Use the results of your Part A measurement for the resistance of R1 and R2 in parallel, ROUNDED to the next whole number, and dial it into the top row of the box.

NOTE: none of your resistances for Part A will ever approach even 1k-Ohm, therefore, only the top row of dials need to be adjusted; the bottom row should be set to zero.

If your parallel resistance measurement for R1 and R2 was 183.1 ohm, round to the next whole number, 184, and set the dial so that the 1-Ohm is at 4, the 10-Ohm is at 8 and the 100-Ohm is at 1 – the digits become the settings of the dials!

Once this is setup, simply measure the voltage across the red and black leads as well as the current passing through the box and move onto Part D.

Stack the Black and Gray LVPS’s as shown.

NOTE: The Black LVPS is a mini-computer and takes a while to boot properly. It was setup such that it will output only 5V!

To create the combination circuit, connect R1 and R2 in series as shown.

ERROR: R1 should be on the right and R2 should be on the left; nevertheless, the wiring and the techniques used to measure voltage and current depicted by these images are absolutely correct.

Connect the two black leads from the two LVPS’s together as shown.

Connect the Gray LVPS’s red lead to the appropriate resistor’s free end, as shown.

Connect the Black LVPS’s red lead to the appropriate resistor’s free end, as shown.

Remember, the Black LVPS is programmed to only produce 5Volts; the Gray LVPS must be set to the required 9Volts.

Next, connect the R3 resistor to the R2 resistor with lead as shown.

NOTE: this lead could have been placed on either resistor but for clarity due to the limit work space, the right resistor was chosen instead of the left resistor).

Complete this circuit by attaching the two black leads from the LVPSs onto the other end of the R3 resistor.

The easiest way to approach the measurements, is to do the voltage measurements first. You must be careful and apply the polarity as indicated; if you ever measure a negative number, it means your polarity is reversed, make a note of that in your lab notebook and fix the wiring FOR THE DMM ONLY.

This is how the voltage for the R2 resistor would be taken; again, if the meter yields a negative value, fix the meter’s wiring, not the circuit’s wiring.

The voltage for the R3 resistor.

Make a hole here to measure the current through the R1 resistor.

Plug the hole with the current meter.

Make a hole here to measure the current through the R2 resistor.

Plug the hole with the current meter.

Make a hole here to measure the current through the R3 resistor.

Plug the hole with the current meter.