Solution Found!
The circuit shown in Figure DP 3-11 is designed to help orange growers protect their
Chapter 3, Problem DP 3-11(choose chapter or problem)
The circuit shown in Figure DP 3-11 is designed to help orange growers protect their crops against frost by sounding an alarm when the temperature falls below freezing. It contains a thermistor that has a resistance \(R_0=620 \Omega\) at the temperature \(T_0=20^{\circ} \mathrm{C}=293^{\circ} \mathrm{K}\) and \(\beta=3330^{\circ} \mathrm{K}\). (See problem DP 3-9.)
The alarm will sound when the voltage at the - input of the comparator is less than the voltage at the + input. Using voltage division twice, we see that the alarm sounds whenever
\(\frac{R_2}{R_{\mathrm{T}}+R_2}<\frac{R_4}{R_3+R_4}\)
Determine values of \(R_2, R_3\), and \(R_4\) that cause the alarm to sound whenever the temperature is below freezing.
Questions & Answers
QUESTION:
The circuit shown in Figure DP 3-11 is designed to help orange growers protect their crops against frost by sounding an alarm when the temperature falls below freezing. It contains a thermistor that has a resistance \(R_0=620 \Omega\) at the temperature \(T_0=20^{\circ} \mathrm{C}=293^{\circ} \mathrm{K}\) and \(\beta=3330^{\circ} \mathrm{K}\). (See problem DP 3-9.)
The alarm will sound when the voltage at the - input of the comparator is less than the voltage at the + input. Using voltage division twice, we see that the alarm sounds whenever
\(\frac{R_2}{R_{\mathrm{T}}+R_2}<\frac{R_4}{R_3+R_4}\)
Determine values of \(R_2, R_3\), and \(R_4\) that cause the alarm to sound whenever the temperature is below freezing.
ANSWER:
Step 1 of 4
The thermistor resistance 
Freezing occurs when the temperature of air falls below the freezing point of water
At
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