ME 368Introduction to Lab Laboratory 0

Laboratory 0

Lab Introduction / MyDAQ Setup

Required equipment:

1st day (roughly, sections 1 – 5 below)

Variable DC power supply

Digital multimeter

Resistance substitution box

Fixed resistor

Any old MyDAQ or compactDAQ card

2nd day (roughly, section 6 below)

Your own laptop and MyDAQ

1.0 Welcome

Your lab instructor should introduce himself / herself, explain how lab groups will be setup for the semester, mention lab policies (be on time, put stuff back), give a brief overview of all the labs, give a brief overview of this lab, and answer any questions you may have.

2.0 Measuring the voltage of a power supply

  • locate the DC power supply (PS)
  • locate the digital multimeter (DMM)
  • turn both of these boxes on
  • turn PS current and voltage knobs to zero (counter clockwise)
  • hook banana patch from OUTPUT - on PS to COM on DMM
  • hook another banana patch from OUTPUT + on PS to V on DMM
  • select voltage on the DMM
  • select the 20 volt range on the DMM
  • turn up the voltage knob and observe the response on the PS and DMM (Current limited)
  • turn the voltage knob back to zero
  • turn the current knob to about half way
  • turn up the voltage knob again and observe the response on the PS and DMM

1 point: demonstrate to your lab instructor that you understand the difference between current limited and voltage limited operation

  • disconnect the banana patch cables
  • find the insulated single conductor wires in the bins at your station
  • insert one of these wires into the + 5V OUTPUT terminal on the PS
  • insert another one into the - 5V OUTPUT terminal on the PS
  • use either banana plug to micro clip or banana plug to aligator clip to connect the DMM to the wires of the PS
  • select voltage on the DMM
  • select the 20 volt range on the DMM
  • note the voltage measured
  • turn the voltage knob and notice that it does not affect this output
  • note that the voltage measured is not exactly 5V

1 point: associated with the last several bullets, describe something you learned to your lab instructor

3.0 Direct resistance measurement

  • find the Resistance Substitution Box (“R Sub Box”)
  • the resistance value is the sum of all of the switches that are switched up and the internal resistance
  • this resistance is the resistance between the red and black posts
  • the green post is isolated from everything else, use it simply as a separate, convenient place to connect things
  • flip all of the switches on the R Sub Box off (down)
  • hook banana patch from COM on the DMM to the BLACK post on the R Sub Box
  • hook another banana patch from Ohm on the DMM to the RED post on the R Sub Box
  • select resistance (Ohm) on the DMM
  • select the lowest range
  • read the resistance, this is the internal resistance of the R Sub Box
  • increase the range on the DMM and observe how the resistance measurement changes
  • the error increases as the range size increases, therefore the best range to use is the lowest range that is not maxed out

1 point: have your lab instructor give you a hypothetical resistance to measure and respond with the best range with which to measure it

  • flip some of the switches and measure the resistances (keep the DMM in the lowest appropriate range)
  • measure the resistance in the same manner between the RED and GREEN post on the R Sub Box
  • measure the resistance in the same manner between the BLACK and GREEN post on the R Sub Box
  • the last two resistances measured should be very high, which means that the GREEN post is isolated from the BLACK and RED posts

4.0 Some practical / mechanical details

  • note that each R Sub Box post has a hole through the bottom of it; this hole can be used to connect a bare wire to the R Sub Box
  • insert a wire through the hole and screw the colored cap down to clamp the wire into place
  • more than one wire can be inserted into and clamped to each post
  • do not wrap wires around the bottom of the post, this does not ensure a good connection
  • best practices: use only banana plugs and bare wires to connect to these types of terminals; micro clips and aligator clips are best for clamping to wires, they should not be used on posts, banana plugs, or to connect to each other; to minimize clutter, keep your wires short with as few connections as possible

1 point: demonstrate your ability to properly connect a bare wire to a screw terminal block (e.g., on a MyDAQ or compactDAQ module) and your ability to connect a BNC cable to a BNC jack

  • take note of the locations of all the cables, connectors, etc. they should always be returned to the correct locations at the end of lab

5.0 Voltage divider review; indirect resistance measurement

1 point: sketch a voltage divider circuit and explain it to your lab instructor

  • find the fixed resistor at your lab station or obtain it from your lab instructor
  • connect the resistor to the GREEN and BLACK posts of the R Sub Box
  • connect the OUTPUT + and - of the PS to the RED and GREEN posts of the R Sub Box, respectively
  • the PS is now set to power the two resistors (fixed resistor and R Sub Box) in series
  • set the current knob to about half way, and set the voltage knob to about 5 volts
  • connect the COM and V of the DMM to the GREEN and RED posts of the R Sub Box, respectively

1 point: improve the sketch you last showed your lab instructor so that the 1-to-1 correspondence to the circuit you just built is obvious

  • select voltage (V) on the DMM and select an appropriate range (one that is greater than 5V)
  • change the R Sub Box value and observe the resulting voltages (should it change?)
  • connect the COM and V of the DMM to the GREEN and BLACK posts of the R Sub Box, respectively
  • change the R Sub Box value and observe the resulting voltages
  • choose an R Sub Box value that gives a measured voltage as near 2.5 V as possible
  • calculate the fixed resistance from the PS voltage, R Sub box resistance, and DMM measured voltage

1 point: show your calculation to your lab instructor

  • use the internet to determine the value of the resistor (google search "resistance color code")

6.0 MyDAQ setup

It takes time to install LabVIEW and the MyDAQ driver and to get everything running. You are encouraged to do these tasks outside of lab so that all you need to do for this part in lab is just get your 3 points and leave. Ideally, before you come to lab W or R, you will have run the Elvis software and practiced measuring the voltage between the DGND and 5V screw terminals on your MyDAQ.

3 points: demonstrate for your lab instructor the measurement of an R Sub Box resistance using your own laptop in conjunction with your own MyDAQ

Your lab instructor will try to help you debug your setup if you are having trouble. Your lab instructor may also be able to get additional help from Joshua Jankowski (3rd floor ME) if he/she cannot help directly. If you get help Weds or Thurs you can get the 3 points at the start of lab Mon or Tues next week.

12/6/2018 3:27:42 PM