122-28029 Parallax Inc, 122-28029 Datasheet - Page 71

• Manufacturer Part Number: 122-28029
• Description: GUIDE STUDENT SMART SENSORS
• Manufacturer: Parallax Inc

Specifications of 122-28029

• Accessory Type: Manual
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Smart Sensors
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

distance calculations. Air temperature, on the other hand, can cause measurable distance
errors. The speed of sound increases by 0.6 meters per second (m/s) for every degree-
Celsius (°C) increase in temperature. Since the speed of sound is about 331.5 m/s at 0
°C, we can use this equation to calculate the speed of sound at a given temperature.
Below are examples for the speed of sound at two fairly comfortable, but slightly
different indoor temperatures.
Example 1: Calculate the speed of sound at 22.2 °C, which is approximately 72 degrees
Fahrenheit (°F).
Example 2: Calculate the speed of sound at 25 °C, which is 77 degrees Fahrenheit (°F).
How much of a difference does this make to your distance measurements? We can
calculate the percent error this will propagate with the percent error equation.
If the predicted temperature in the room is 72 °F (22.2 °C), and the actual temperature is
77 °F (25 °C), the error is 0.49 percent. Half a percent error would cause you to have to
C
C
C
%
air
air
air
Converting from °F to °C and Visa Versa
To convert a degree-Fahrenheit to Celsius, subtract 32 from T
measurement), then divide by 1.8. The result will be T
from Celsius to Fahrenheit, multiply T
error
(
=
(
22.2
25°C
331.5
=
°
)
actual
C
=
)
+
=
331.5
T
(
0.6
C
331.5
predicted
=
(T
-
×
F
predicted
+
-
T
32)
C
+
(
0.6
)
(
0.6
÷
m/s
1.8
×
25
×
22.2
×
)
C
100%
m/s
by 1.8, then add 32. The result will be T
m/s
Chapter 2: The Ping))) Ultrasonic Sensor · Page 59
=
T
F
)
346.5
= .
=
1
8
344.8
×
T
C
C
, the Celsius equivalent. To convert
m/s
+
32
m/s
F
(the Fahrenheit
F
.