Physics 434 Module 1
• Reminder about the computers:
– You can save VI’s on the local disk.
• put them on the desktop
• put them into My Documents\your_name
• (But beware: no backup, no protection)
– Or just use catalyst for temporary storage!
• Review of last week – some important LV lessons
– Controls, indicators, while (and for) loops
– Right-click! (I’m a Mac user so I always forget this.)
You’ll also start picking up shortcuts, e.g.,
– Tool options: auto, menu, or tab
– Cntrl-b (remove bad wires, with care)
– Cntrl-z (undo)
– Shift-right-click: bring up the tool menu
Physics 434 Module1A
1
The next two weeks
• Introduction to DC I/O capability of the PCI-E board
and use of the break-out box
–  10 V out, up to 8 measurement channels, also 10 V.
• Wire a simple circuit on a breadboard
– Layout guidelines
– Oscilloscope, DVM auxiliary tools
Physics 434 Module1A
2
The “voltage divider” circuit.
The single most important circuit.
ach0
dac0
ach1
R1 = 100
R2 = 200
Physics 434 Module1A
3
Properties of the “DAQ” board
– up to 16 input channels, multiplexed to a 12-bit ADC
• (we use four, configured as two differential)
– 2 output channels (2 12-bit DACs) (we use one)
– Questions:
•
•
•
•
what does 12-bit mean?
Linear A vs. D: but what are the offset and scale factors?
Can you control them?
Differential vs. single-ended?
Physics 434 Module1A
4
Computer
Breakout-box
The PCI-MIO-16E-4 board
Physics 434 Module1A
5
Differential input
Physics 434 Module1A
6
Wiring to be done to the “Breakout box”
• Differential inputs: red/black pair to BNC
– Input channel 0 (ach0): ACH0/ACH8 [68/34]
– Input channel 1 (ach1): ACH1/ACH9 [33/66]
– (beware touching the BNC connector to anything)
• Output: two wires long enough to reach breadboard
– Output channel 0 (dac0): DAC0/A0GND [22/55]
• Note that while the inputs are “floating”, the output is
not: it is relative to ground.
Physics 434 Module1A
7
Testing: get the testio vi
• copy Module1.llb to your space; open it, then the vi test_io
• We rarely build vi’s completely from scratch: this is a framework,
around a custom vi to do the I/O
Physics 434 Module1A
8
Features of the test framework
• Knobs, dials for the input, two outputs
• A special test mode – an important feature for
experimental design
• I/O put into a special sub-VI with three “frames”
–
–
–
–
Set dac0 using a DAQ assistant
Delay (default 0) (allow system to adjust to change)
Read ach0 and ach1 with another DAQ assistant.
All set for -10 to +10 volts: you may want to change later.
Physics 434 Module1A
9
Procedure for this week
•
•
•
Set the test mode of the test_io VI to produce outputs according to your
expectation.
Revise the VI so that you can generate a graph like the one in
graphdemo vi (also see figure 8.19 in text).
Wire up the board with the two resistors, and make connections to the
breakout board, to correspond to the question. Neat layout is very
important, for you to understand, and for us to help!
Physics 434 Module1A
10
Example layout
ach0
ach1
daco
Physics 434 Module1A
11
Hints
•
•
•
•
VI: keep neat, use labels and add comments
Test each piece first! You can have separate vi’s
Breadboard: Lay out the circuit neatly: use the space
If appropriate, test the circuit with power supply, DVM
or scope before trying to run the VI.
• Keep good notes: a personal lab book is best
• Problem: Use reference material, help files, etc.
• More problems: Ask the TA
Physics 434 Module1A
12
Requirements for the VI
• Sweep through predefined set of values for setting
V0 (perhaps a for loop)
• Record values for V1 and V2 for graphs and analysis,
using either or both experimental or test modes.
• Plots:
– V1 and V2 vs. V0: the data and your expectation (test mode) perferably on
the same graph, each labeled (so 4 graphs on the same plot) or two plots)
– V2 vs. V1 (as in the pretest)
• Analysis:
– Discuss the graphs and comment on the results
– Measure and comment on the ratio V2/V1 and the sum V2+V1. (You may
want to have plots or at least some measurements)
Physics 434 Module1A
13
Turning in your VI(s)
• Operate | Make current values default – needed to
record your results by saving the graphs
• File | VI properties | Documentation:
write a little report, containing your name(s), purpose
of the VI, implementation features, conclusions.
• Submit multiple VIs in an llb, like Module1.
14
Next week’s circuit (you may need to
remind yourself how a FET works)
The IRF511 power
MOSFET Transistor.
Set the
voltage
here…
G
D
S
And
measure the
voltage and
current here
Physics 434 Module1A
15