Download Lab #10 - Montana State University

MONTANA STATE UNIVERSITY
DEPARTMENT OF MECHANICAL ENGINEERING
Mechanical Engineering Laboratory
ETME360 Spring 2017
R. Larson
Lab 10 VARIABLE CAPACITANCE TRANSDUCER APPLICATIONS:
MEMS ACCELEROMETERS
Goals:
1. Investigate the characteristics of a MEMS Capacitive Accelerometer, in a selfguided laboratory experience.
2. Generate a laboratory test plan and execute the plan.
3. Utilize a laptop PC-supported Data Acquisition System to allow versatility in
testing location.
References:
A. Wheeler & A Ganji, Introduction to Engineering Experimentation
ETME360 Lecture & laboratory instruction
Equipment:
PCB Piezotronics Model 3801D1FB20G/M001 Capacitive Accelerometer
- Sensitivity varies with unit, approximately 99.6 mV/g (= 10.16 mV/m/s2)
- Offset Voltage varies with unit (calibration required!) For most units this value is
approximately = -12.0 mV @ 0 g.
Laptop Computer with LabVIEW Software
Wire or cable sufficient to provide both accelerometer excitation voltage and signal
acquisition
Discussion:
PCB Piezotronics corporation states that the "series 3800 Variable Capacitance
Accelerometers achieve true DC response for measuring uniform or constant
Acceleration and low frequency vibration." In this lab, each self-defined group is
responsible for choosing a project of interest that involves acquisition and
interpretation of acceleration data.
The accelerometer form factor is a 1" cube. The unit is sensitive in a single axis only.
Excitation voltage (minimum) is 5 volts DC excitation, which can be provided from
the USB-6008 or USB- 6009 DAQ system. Output signal is a function of the
acceleration of the unit, per Sensitivity specifications. The accelerometers can be
temporarily affixed to test articles using tape, hot glue, etc. Don’t cut the
accelerometer lead wires!
Sampling rate of the LabVIEW code should be selected with consideration of the test
being performed: Impact events require very high sampling rates and produce large
volumes of data in a short time.
Procedure:
A. PRE-LAB Assignment
1. Choose your group members: Four sets of equipment are available, so for each
lab please self-select a groups of 4 or fewer individuals.
2. As a Group, define your measurement subject: Choices are endless, for
instance one could monitor the acceleration of a tennis racquet or bicycle, the
response of a bicycle bouncing over a curb, the deceleration of a dropped object.
And since F=M*A, if the accelerometer is attached to an object of known mass
the Forces involved in certain phenomenon can be calculated. Transient events
such as impacts can be recorded. For example, how much difference in force is
noted between impacts on a hard surface versus a padded one? Lots of
opportunities exist, within reason. With regard to project selection, generally
SIMPLER is BETTER!
3. Submit your group's membership and project selection to the D2L Dropbox
prior to the start of the lab, and BRING A COPY TO THE LAB MEETING. This
document should define
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the specific phenomenon you intend to investigate,
the data you will gather, and
the location of testing.
Use a format similar to the format I used in a typical ETME360 Lab Handout.
Rules:
- All equipment must be returned intact and undamaged.
-All MSU, Local, State, and Federal rules/laws/procedures apply. (No guns on
campus, no speeding, etc. PAY ATTENTION TO SAFETY!)
- You MUST write and use LabVIEW code to control a DAQ system to obtain
acceleration data.
- You MUST complete your experiment during the scheduled 2 hour lab period.
- Results must be suitable for publication/dissemination in all public forums.
- Course/Lab instructors or T/A may disapprove any request if safety,
procedural, or other issues are noted.
B. Laboratory Experiment
Once your proposal is approved, carry out your plan! You may wish to write
your LabVIEW code prior to the lab period to give more time for project execution.
Once completed, be sure to check data integrity immediately after each test to
ensure you recorded data!
Results:
1. You wrote the requirements, and you must conform to them. Your Pre-lab
document will be used to evaluate your results. For instance, if you specified
comparison with some standard or have a project involving complex calculations,
you must include these items in your report.
2. Prepare and include correctly formatted graphs of the results of each test, as
defined in your test plan runs. INCLUDE PHOTOS of your test.
3. Draw a meaningful conclusion from your results. (This conclusion must be
supported by the data!)
4. Compile other elements of your report in the usual manner: The Sample
Calculations section should be complete and accurate. Clearly discuss any data or
sampling issues that might affect accuracy of your derived results.
Note: Do not submit raw voltage data downloaded from the PC with your report:
Your Acceleration graphs will provide sufficient information for the purpose of
determining performance. Include all other pertinent data sheet items, copies of the
LabVIEW code, etc.