P13472 CHANGE OF
RESISTANCE TEST
STAND
DETAILED DESIGN REVIEW PACKET
FEBRUARY 20, 2013
FACULTY GUIDE:
DR. BENJAMIN VARELA
TEAM MEMBERS:
JACOB LENNOX
COLIN PAYNE-ROGERS
Detailed Design Review Agenda
Meeting Purpose: To review experimental interface relay circuit design, proof-ofconcept experimental results, actual interface relay circuit design, bill-of-materials, risk
assessment and MSD II test plan
Review Materials: Detailed Design Review Packet (this document)
Meeting Date: February 20, 2013
Meeting Location: Cooper Crouse-Hinds
Meeting Time: 11:30AM
Meeting Timeline
Topic
Customer Specifications
Proof-of-Concept Circuit
Design, Hardware
Proof-of-Concept
Experimental Results
Relay Circuit Design
Bill of Materials
Test Plan
Page (this packet)
2-4
4-7
Required Attendees
Everyone
Everyone
8-9
Everyone
9-10
11
12
Everyone
Everyone
Everyone
Customer Specifications/Needs
The following table was created using a template file available from the Senior Design
MyCourses. Importance of “1” means it is a must-have specification.
Cust.
Need #
CN1
CN2
Importance
Description
Comments/Status
1
Measure the temperature
using the change-ofresitance (linear regression)
method, per UL844
standard.
The data will be stored in excel-compatable files and a macro will
be written for data reduction to be done on the same computer,
but not by LabView (so that a cheaper version of the LabView
software can be used on the test stand)
Design and build the
interface relay circuit.
The interface relay circuit has been designed, a preliminary proofof-concept experiment has been performed to demonstrate the
veracity of the circuit, the design and experimental results will be
presented to the customer at the detailed design review. It should
be noted that there are components to the relay circuit that are not
included in the design yet (capacitor in/out, to ballast, to lamp,
from balast, etc...see Cooper circuit design).
1
2
CN3
1
Select and purchase a
multimeter capable of
reading coil resistance with a
resolution of 0.01 Ohms.
CN4
1
The multimeter must be able
to be calibrated.
CN5
1
Incorporate a thermocouple
to measure the ambient
temperature of the ballast
core.
CN6
1
The LabView program will
be able to measure the
resistance of up to 6 coils.
CN7
1
The first "stabilized"
measurement should be
taken within 5 seconds.
CN8
1
Readings must be taken one
at a time.
CN9
1
A minimum of 40 readings
must be completed in 30
seconds.
CN10
1
Allow the operator to test all
of the coils or any
combination of coils.
CN11
1
Make a plot of resistance
versus time for each coil,
make a linear regression of
this plot and calculate the
temperature of the coil.
CN12
1
Store the data in up to 9
different portable-format
files.
A multimeter has been selected that is interfaceable with LabView
(it is a National Instruments multimeter) and has the required
resolution. The multimeter is capable of taking 4-wire resistance
measurements and is compatable with the PXI Chassis used in
the design (???).
The current plan to achieve this customer need is to include in the
final design a resistor of known resistance that is always
connected to one channel of the NI switch. The resistance of this
resistor will be tested with various multimeters to ensure its
resistance is known, and the LabView program will include the
ability to measure this resistance, show the difference between the
known value and the measurement, and calibrate the instrument
(hopefully there is a command in LabView to calibrate their
multimeter).
Along with the NI PXI system (multimeter, switch) a multi-function
DAQ will be purchased as well. This DAQ had digital
inputs/outputs and will be capable of taking readings from the
thermocouple (that will also be purchased from NI?).
A LabView "switch" (16 or 32 channel) will be incorporated into the
final design that can be controlled from LabView to take the
measurements of any combination of coils. The program will be
written with a user-friendly interface that will allow for the operator
to choose which coils need to be measured.
The response time of all of the LabView equipment is fast enough
that we should have no problem achieving this. The "power
circuit" switches have a delay when being turned off, but we can
account for this in the LabView programming so that the National
Instruments hardware never comes into contact with the voltage
from the ballast.
The capability of the LabView switch to change channels at a high
frequency should take care of this. There is a chance that the
LabView program will have to "delegate" a certain amount of time
for each 4-wire measurement so that the multimeter has time to
stabilize before the next measurement is going to be taken.
As stated above, the speed at which all of the National
Instruments hardware is capable of switching and operating at
should make this requirement very easy to achieve. It is likely that
about a half a second will be delegated to each reading, which will
hopefully be enough time for the multimeter to read the resistance
of the coil before the switch changes coils.
This will be achieved in the LabView programming. Each channel
(or set of channels) in the NI switch will be designated to a certain
coil. The channels that will be used during each test will be
chosen by operator. OR, all channels will be used in each test but
the channels that will be output to the excel file for data reduction
will be chosen by the operator.
This will be done using a macro in excel. It may be possible to
incorporate the macro into a BAT file that the operator can run
from the desktop and use to choose which files contain the data
that needs to be reduce. How this data reduction works depends
on how much Cooper trusts its operators to use the excel macro
(or the engineers?).
Although the LabView program has not been written yet, it is
assumed that the number and types of files that the program
outputs can be incorporated into the LabView program relatively
easily.
3
CN13
CN14
CN15
1
Operator can input date,
time, coil material…program
has the following functions:
pre-run test, run auto-test,
view results, print results,
terminate.
1
Test stand must be
contained within a rolling
enclosure.
This enclosure will be designed at the beginning of MSD II…it will
use some form of aluminum bracket and plywood and whatnot…once the LabView parts and laptop are on hand the
dimensions and specs of the cart can be determined.
1
The interface relay circuit
must operate within the
ballast operating range 120480VAC, 30-40Hz.
With the power circuit and the measurement circuits separated by
relays controlled by LabView, this customer need is satisfied by
ensuring the electromechanical relays are rated to operate at the
correct voltage, which they are.
Achieve via LabView interface, most likely the interface will be
more customizable than this to achieve some of the above
customer needs.
Cust. Need #: enables cross-referencing (traceability) with specifications
Importance: Sample scale (1=must have, 2=nice to have, 3=preference only), or see Ulrich exhibit 4-8.
Experimental Circuit Design, Hardware
The following pages detail the conceptual experimental design and images of the
hardware setup used during the experiment. The goal of the experiment was to show
that two separate (in this case manually operated) control circuits could be used to
provide three instances of operation:
1. Off – No power to the ballast, no measurements being taken with the Multimeter
2. Power – Supplying the ballast with power, severing the connections between the
ballast and the Multimeter so the measurement hardware is not damaged during
ballast operation
3. Measure – Cut off power to the ballast and restore the connections between the
ballast coils and the Multimeter so the 4-wire resistance measurements can be
taken
4
Figure 1: Proof-of-Concept Experimental Circuit Design
5
Figure 2: An overview of the experimental setup, digital Multimeter and ballast
both connected.
Figure 3: Close-up of the “relay circuit(s)”, power supplies (right),
measurement control circuit (left, top), power control circuit (left, bottom).
6
Figure 4: Close-up of the measurement control circuit, wiring used to achieve
parallel connections to the relays (so that each sees 24VDC).
Figure 5: Close-up of the power control circuit, two terminal blocks used as
junctions between the ballast connections (com, 120VAC to ballast), the
measurement connections (to Multimeter) and supply connections.
7
Experimental Circuit Design, Results
In addition to the typical ballast testing (4-hours of ballast operation followed by the
initial temperature calculation) an additional test was performed to ensure that the
experimental circuit was not offsetting the resistance measurements. Coil 1 and Coil 2
resistance measurements were taken by connecting the 4-wire measurement leads from
the ballast directly to the Multimeter and then compared to measurements taking by
connecting the ballast to the experimental apparatus and taking resistance
measurements through the apparatus. The following table summarizes these results
(note that the difference between the values is an order of magnitude lower than the
required measurement resolution in the PRP, and that the difference is not consistent
from coil to coil):
Direct-to-Ballast
Through Relay Circuit
Coil 1 Resistance (Ω)
3.798
3.801
Coil 2 Resistance (Ω)
2.678
2.677
Figure 7: Room Temperature measurements taken at RIT.
Using the experimental setup detailed above, the following “4-hour” results were
obtained (blue) and compared to the results provided by Cooper Crouse-Hinds (red, see
table).
Figure 6: Comparison between test data received from Cooper and the
experimental test performed at RIT.
8
Initial temperature calculations:
RIT
Cooper
Rc from
DMM
Rc (Ω)
Th (°C)
Rh (Ω)
Rc (Ω)
Th (°C)
Rh (Ω)
4.1
51.75
4.57
3.801
55.92
4.3037
not from
DMM
3.66
86.52
4.57
3.361
93.94
4.3037
Figure 7: Tabulated calculations.
There are a few possible reasons why the data gathered at RIT is different from the data
gathered at Cooper:





The ballast was operating without the lamp attached at the RIT test. This may
change the temperature as well as internal ballast operating conditions.
The ambient temperature for ballast operation was different in each case.
The size of the room in which the experiment took place was much larger at RIT.
The only wires of the ballast connected to anything during the test were the
common and 120VAC wires. The capacitor, or any other wire, were not
connected.
The voltage being supplied to the ballast may have been different.
Relay Circuit Design
The prototype change-of-resistance test stand design proposed below is based heavily
on the concept used to design the experiment above. Three “circuits” will control the
operation and testing of the ballast. The first circuit, the “power circuit” will supply the
ballast with power (when engaged) and allow for a method to cut power from the ballast
separately from the method used to being taking resistance measurements. This circuit
is in place to ensure the hardware does not “see” high voltages being supplied to the
ballast. The second circuit, the “measurement circuit” is similar to the power circuit in
that it is in place as a “gap” between the ballast/power circuit and the Multimeter. This
circuit will “engage” only after the power circuit is disengaged, and only then can
measurements begin. The third circuit consists of the National Instruments (NI) switch
and Multimeter. This hardware is controlled by LabView and lies in the NI “PXI Chassis”.
This circuit is responsible for switching from resistance measurement to resistance
measurement during the data acquisition period of ballast testing (and only after the
power circuit has disengaged and the measurement circuit has engaged). The NI PXI
Chassis will also include a multi-function DAQ that will allow LabView to control the
power circuit and measurement circuit. This DAQ can also take measurements from the
required thermocouple. The hardware required to design and build this circuit is
outlined on page 9 of the packet.
9
Figure 9: Basic concept design for the relay circuit, with major hardware
10
Bill of Materials
Accessory
PXI Chassis
Vendor
NI
PN
781162-01
Description
NI PXIe-1073
Indv. Cost
$ 1,499.00
Chassis Power Cord
DMM
NI
NI
763000-01
780011-01
NI PXI-4065
$
9.00
$ 1,499.00
1
1
$
9.00
$ 1,499.00
Relay Module
NI
778572-66
NI PXI-2566
$ 1,080.00
1
$ 1,080.00
11
Quantity Cost
1 $ 1,499.00
Relay Terminal
Block
NI
778717-66
960903-02
Power Circuit Relay
NI
McMaster
Carr
7230K91
Power Circuit Relay
Allied Elec
USB DAQ
NI
System Assurance
TB-2666
$
277.00
1
$
277.00
$
310.00
1
$
310.00
4PST
$
76.91
4
$
307.64
70198625
DPST
$
10.07
1
$
10.07
779051-01
USB-6008
$
169.00
1
$
169.00
12
Circuit Total
Labtop
Labview Lisence
Miscellaneous
NI
Cart etc.
*Highlighted Boxes are approximate costs
$ 500.00
$ 999.00
$ 1,000.00
1
1
1
Total
$ 5,160.71
$ 500.00
$ 999.00
$ 1,000.00
$ 7,659.71
Test Plan
The following test plan was created using a test plan template document available on
MyCourses and then copied from excel:
Number Description
Test the ballast temperature/resistance measurements with a borrowed 4-wire multimeter
but the updated relay circuit (using "final hardware" and one coil rather than "experimental
1
hardware"). Show the exponential decay, and the difference in resistance measurements
when measuring the ballast directly and through the circuit.
Test the ability to switch between different coil measurements using the NI switch,
manually and automatically, and then verify the results from test #1 for the same coil when
2
switching to the other coils inbetween each measurement (possibly taking all coil
measurements)...with the borrowed multimeter still?
Show that initial measurements are capable of being taken within 5 seconds, and that all 6
coil measurements are capable of being taken at the required rate. This would be a final
3
"proof-of-concept" test, showing that the LabView program can be used to measure 6 coils
as quickly as needed and can spit out the correct data (data compared to #1). The NI
multimeter used this time to show that it is calibrated as well as the borrowed multimeter.
Test the calibration routine by using a "correct" and "incorrect" calibration. The "correct"
calibration for the routine should give the correct ballast (room temperature) results while
4
the "incorrect" calibration should offset the ballast resistance measurements? This test
depends on the final method for calibration.
13
Timeline
14