Reference no: EM133656528

Aim

• Investigating the principles ofa basic circuit.
• Learning the correctprocedurefor using a Digital Multimeter as a Voltmeter and Ammeter.
• Measuring various electrical quantities such as current and voltage.
• Constructing and making measurements with a simple capacitance-based mass sensor
• Constructing journal quality tables and graphs (post lab).

PRE-LAB - THIS WILL BE COVERED IN THE PRACTICAL

Given the image of multimeter provided:
1. Try to identify the term (with units) measured at each individual (or grouped) setting of the rotating knob.
2. Do any of them have maximum values that must not be exceeded? If so which ones?
3. Set the DMM to measure up to 7.0 amperes with the correct lead placements and knob position.
4. Set the DMM to measure resistance with the correct lead placements and knob position.
Equipment
1. DC power supply
2. Two Digital MultimetersDMM and leads
3. Set of resistors and connectors
4. NTC Thermistor
5. Capacitor Mass Sensor Kit
6. Salinity Sensor kit

General instructions:
Complete a log book of your work briefly discussing what you have learned or discovered.
There may be some differences between the DMM and power supply described in this practical and what is available in your lab - your demonstrator will guide you if this is the case.Bear in mind however that the functionality of the DMM and power supply will be the same regardless of the model/manufacturer.

You will be provided instructions on how to construct journal quality tables and figures (graphs). You will use these tables and graphs to submit your results of the practical.
You will work in pairs to perform this experiments.Part III of this practical leads into the construction and use of a simple capacitance-based mass sensor.The assembly required in Parts III and IV will not take long - one partner may build the mass sensor.

Part I :Working with a Digital Multimeter -Collecting the data

1. Record the nominal (listed) value of your resistor and its uncertainty (based on the colour code).

Colour code: ____________________________

Resistance and Uncertainty: ____________________________

2. Multimeters can be "set" to measure different quantities based on the position of the rotating knob AND the locations of the leads.
a. Set upone DMM to measure resistance in Ohms
i. Use the DMM to check the resistor's value
Measurred resistance: _________________________________
ii. Is the nominal resistance from the colour code correct within the uncertainty range?
_________________________________

b. Set up one DMM as an Ammeter to measure in milliamps, mA(to be used in Series with the resistor).
c. In what two ways is this arrangement different if you wanted to measure up to 10 A?
i. _________________________________

ii. _________________________________
d. Set up the other DMM as a Voltmeter (to be used in Parallel across the resistor).
e. Check with a demonstrator before proceeding.

3. What is the maximum current rating for the Ammeter in step 2(a)? ______________

4. All devices, including sensors, have maximum values for particular properties such as force, pressure, temperature, or in our case current.
a. Given the nominal resistance of your resistor, what is the maximum voltage you can apply across it before the Ammeter fuse will blow? _____________
b. Does the resistor itself have a maximum current rating? After you have completed your graph for this practical, consider what would happen to the resistor if you exceeded the maximum current rating. (In reality it's a power rating, but that's not too important right now.)

5. We will construct the following circuit:

6. Connect the ammeter DMM in series with the resistor and connect it back to the ground of the power supply. Then add the voltmeter DMM across the resistor.

7. Do not turn anything on. Check with the demonstrator.

8. Ensure the power supply CURRENT and VOLTAGE are set to zero. Turn it on, and adjust the CURRENT until the CV light is lit. (This step varies from one device to another so you'll need to be flexible here.)

9. Increase the (nominal) VOLTAGE on the power supply and record it, the voltageacross the resistor, and the current through the resistor. Be sure to include uncertainties.

10. Record the values in Table 1, and repeat for a total of 6 - 8 values in a range between 0-12v.

11. Are any of your readings negative? Discuss this with a demonstrator.

Part II :Building a Capacitance-based Mass Sensor & Collecting the Data

A. Building a Simple Mass Balance

1. Cut two pieces of Aluminium foil about 5" x 6". You don't need to be exact.

2. Take the longer side and put a fold on one edge, so the foil area becomes 5" x 5".Again you don't need to be exact

3. Attach each Aluminium square foil down centrally onto a piece of A4 paper. Use Sellotape along the edges of the three sides that don't have a fold on them.

4. You now have two pieces of A4 paper with an aluminium square attached to them.Onto the folded edge of each Al square, attach a paper clip carefully so as not to tear the Aluminium.Onto each paper clip, attach an alligator clip of a lead that will go to the DMM.

5. Ensure the Aluminium squares are facing upwards.Now place a piece of A4 paper or plastic sheet onto the top of one of them and take the other Al/paper sheet and turn it to make a sandwich e.g., paper : Al - plastic or A4 paper - Al: paper.The foil squares should align with each other.The paper or plastic in the middle will act as what is known as the capacitor's dielectric layer.We now have a simple capacitor-based mass balance.

B. Making Measurements with your Mass Balance

1. Attach the wire/alligator clips from the capacitor to the DMM.

2. Move the Red DMM probe from the V/? input jack to the Cx(or -||- )input jack.Leave the black probe in the COM input.Ask the demonstrator if you are unsure.

3. Depending on DMM, you may need to switch the dial on the DMM to read capacitance (Cxor -||- icon on the dial) on then select thenF range.

For instance, if you are using the Digitech QM1321 multimeter, set the rotary dial to to the icon that includes capacitance, (dial pointing about"5 to 12 midnight). position). Then press the function key (FUNC) until nF appears.

4. Place an empty 600 mL beaker on the sensor, over the area of the aluminium squares.Ensure the beaker is centredover the sensing element.Once positioned and you start adding water, don't move the beaker on the sensing element.

5. Measure the capacitance reading on the DMM.This is the baseline measurement (or 0 g water added).Consult your demonstrator if you have any problems

6. Use the 100 mL measuring cylinder to add 50 mL of water at a time.Record the capacitanceagainst total or cumulative massadded, and write it in the raw data table below.Remember we may use a density of 1.0 g/mL so we are adding 50 g of water to the beaker each time

7. Consider any uncertainties in your measurements and record these in the table.

ASSESSMENT

What to hand inbefore you leave the lab:

1. The Practical 1 Raw Data Tables(in-class). Copy or photograph this data as you'll need to use it to construct Journal quality graphs and tables below).