122-28176 Parallax Inc, 122-28176 Datasheet - Page 204

GUIDE STUDENT PROCESS CONTROL

122-28176

Manufacturer Part Number
122-28176
Description
GUIDE STUDENT PROCESS CONTROL
Manufacturer
Parallax Inc
Datasheets

Specifications of 122-28176

Accessory Type
Manual
Product
Microcontroller Accessories
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
For Use With/related Products
Propeller Education (PE) Kit
Lead Free Status / RoHS Status
Lead free / RoHS Compliant, Contains lead / RoHS non-compliant
In terms of byte value, the resolution is 255/1.25 V or 204/V. Our high temperature of
interest, 120 °F (1.2 V), would provide a byte value of 1.2 V x 204 = 244.8 or 245. The
low temperature of interest, 70 °F (0.7 V), would provide a byte value of 0.7 x 204 =
142.8 or 143. So the temperature range of interest covers a byte value change of
245−143 = 102. The majority of our available byte values (0 to 101 and 246 to 255) are
still outside the temperature range of interest.
What line equation would best serve the needs of the monitoring and control system?
Figure 6-9 is the ideal line needed to convert the temperature range of interest to a digital
value for measurement. The temperature range of 70 °F (0.7 V) to 120 °F (1.2 V) is
amplified and covers 0 to 5 volts into the ADC for byte values of 0 to 255.
Let's analyze the line and develop the line equation.
Since the line does not cross at (0,0), b can be calculated given any single known point,
such as 0.7 V and 0 V or 1.2 V and 5 V.
y = mx + b
m = ∆Output/∆Input = (5−0 V)/(1.2−0.7 V) = 5 V/0.5 V = 10
Figure 6-9
Ideal Conversion for
70 °F-120 °F

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