Name
Solution
Real Time Computing Systems
EE 4770
Midterm Examination
18 March 1998,
7:309:30 CST
Alias
Solution
Problem 1
(35 pts)
Problem 2
(30 pts)
Problem 3
(35 pts)
Exam Total
(100 pts)
Good Luck!
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Problem 1:
Design a system to convert temperature,
x
∈
[150 K
,
300 K], to a floating point
number,
temp
=
H
(
x
) =
x/
K, using the new Transducer Z. An algebraic model function for the
new Transducer Z is not available but a lookup table,
HtZ
, is. Table
HtZ
is a 4096element array
which stores the resistance of the sensor in ohms from a temperature of 100 K (
HtZ[0]=870
) to
400 K (
HtZ[4095]=6500
). (The temperature range covered by the lookup table is larger than is
needed for this problem.)
The relationship between the array index and temperature is linear.
(The relationship between temperature and resistance is
not
linear.)
An inverse table,
HtZi
is
also available; element zero,
HtZi[0]=100
, gives the temperature in Kelvins when the resistance is
870 Ω and
HtZi[4095]=400
gives the temperature when the resistance is 6500 Ω. The relationship
between array index and resistance is also linear. The resistance of the new Transducer Z is 1200 Ω
at 150 K and 5000 Ω at 300 K.
(
a
) Design the conditioning circuit and interface routine. If the gain/offset amplifier is used, the
solution can show values for
A
5
and
O
5
instead of each resistor and voltage source, otherwise show
all component and supply values. Show the code for any specialized procedures called.
•
The design should use a 12volt, 16bit ADC and make full use of its dynamic range.
•
Use interpolation to attain maximum precision.
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 Fall '99
 Staff
 Thermodynamics, Resistance, Transducer, model function, largedisplacement pressure transducer

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