Selective temperature control system

Claim 1

A method of determining the temperature to which a thermistor is exposed utilizing a capacitor, a reference resistor, means coupled to the capacitor and actuable to selectively charge the capacitor through either of the reference resistor and the thermistor, means actuable to discharge the capacitor and timing means coupled to the capacitor, comprising the steps: (a) actuating the charging means to charge the capacitor through the reference resistor; (b) operating the timing means to measure the length of time required to charge said capacitor to a predetermined level to obtain a reference charge time; (c) actuating the discharging means to discharge the capacitor; (d) actuating the charging means to charge said capacitor through said thermistor; (e) operating the timing means to measure the length of time required to charge said capacitor to said predetermined level through said thermistor to obtain a temperature charge time; and (f) computing the difference between the reference charge time and the temperature charge time and dividing the difference by the sum of said reference charge time and said temperature charge time to determine the temperature to which said thermistor is exposed.

Claim 2

A method of determining the temperature to which a thermistor is exposed utilizing a capacitor, a reference resistor, means coupled to the capacitor and actuable to selectively charge the capacitor through either of the reference resistor and the thermistor, means actuable to discharge the capacitor and timing means coupled to the capacitor, comprising the steps: (a) actuating the charging means to charge the capacitor through the reference resistor; (b) operating the timing means to measure the length of time required to charge said capacitor to a predetermined level to obtain a reference charge time; (c) actuating the discharging means to discharge the capacitor; (d) actuating the charging means to charge said capacitor through said thermistor; (e) operating the timing means to measure the length of time required to charge said capacitor to said predetermined level through said thermistor to obtain a temperature charge time; and (f) computing the difference between the reference charge time and the temperature charge time and dividing the difference by the sum of said reference charge time and said temperature charge time to determine the temperature to which said thermistor is exposed.

Claim 4

A method of determining the temperature to which a thermistor is exposed in a temperature control system for a space cooling device having an evaporator, an evaporator fan, a compressor, control means including a microcomputer, a capacitor and a reference resistor, the microcomputer including charging means selectively actuable to charge the capacitor through either of the reference resistor and the thermistor, discharging means actuable to discharge the capacitor and timing means coupled to the capacitor, comprising the steps: (a) actuating the charging means to charge the capacitor through the reference resistor; (b) operating the timing means to measure the length of time required to charge said capacitor to a predetermined level to obtain a reference charge time input for said microcomputer; (c) actuating the discharging means to discharge the capacitor; (d) actuating the charging means to charge said capacitor through said thermistor; (e) operating the timing means to measure the length of time required to charge said capacitor to said predetermined level through said thermistor to obtain a temperature charge time input for said microcomputer; and (f) computing in said microcomputer the difference between the reference charge time and the temperature charge time and dividing the difference by the sum of said reference charge time and said temperature charge time to determine the temperature to which said thermistor is exposed.

Claim 5

A method of determining the temperature to which a thermistor is exposed in a temperature control system for a space cooling device having an evaporator, an evaporator fan, a compressor, control means including a microcomputer, a capacitor and a reference resistor, the microcomputer including charging means selectively actuable to charge the capacitor through either of the reference resistor and the thermistor, discharging means actuable to discharge the capacitor and timing means coupled to the capacitor, comprising the steps: (a) actuating the charging means to charge the capacitor through the reference resistor; (b) operating the timing means to measure the length of time required to charge said capacitor to a predetermined level to obtain a reference charge time input for said microcomputer; (c) actuating the discharging means to discharge the capacitor; (d) actuating the charging means to charge said capacitor through said thermistor; (e) operating the timing means to measure the length of time required to charge said capacitor to said predetermined level through said thermistor to obtain a temperature charge time input for said microcomputer; and (f) computing in said microcomputer the difference between the reference charge time and the temperature charge time and dividing the difference by the sum of said reference charge time and said temperature charge time to determine the temperature to which said thermistor is exposed.

Claim 6

An apparatus for determining the temperature to which a thermistor is exposed, comprising: a capacitor; a reference resistor coupled to the capacitor; first charging means coupled to the reference resistor and to the capacitor for charging said capacitor from a first predetermined charge level to a second predetermined charge level through said reference resistor; timing means coupled to the capacitor for measuring the length of time required to charge said capacitor to said second predetermined level to obtain a reference charge time; discharge means coupled to the capacitor for discharging said capacitor to said first predetermined charge level; second charging means coupled to the thermistor and to the capacitor for charging said capacitor to said second predetermined charge level through said thermistor, said timing means measuring the length of time required to charge said capacitor to said second predetermined level to obtain a thermistor charge time; and computing means for computing the difference between the reference charge time and the thermistor charge time, the difference being divided by the sum of the reference charge time and the thermistor charge time to determine the temperature to which the thermistor is exposed.

Claim 7

An apparatus for determining the temperature to which a thermistor is exposed, comprising: a capacitor; a reference resistor coupled to the capacitor; first charging means coupled to the reference resistor and to the capacitor for charging said capacitor from a first predetermined charge level to a second predetermined charge level through said reference resistor; timing means coupled to the capacitor for measuring the length of time required to charge said capacitor to said second predetermined level to obtain a reference charge time; discharge means coupled to the capacitor for discharging said capacitor to said first predetermined charge level; second charging means coupled to the thermistor and to the capacitor for charging said capacitor to said second predetermined charge level through said thermistor, said timing means measuring the length of time required to charge said capacitor to said second predetermined level to obtain a thermistor charge time; and computing means for computing the difference between the reference charge time and the thermistor charge time, the difference being divided by the sum of the reference charge time and the thermistor charge time to determine the temperature to which the thermistor is exposed.

Claim 8

An apparatus for determining the temperature to which a thermistor is exposed, comprising: a capacitor having one end coupled to a voltage source, and another end coupled to said thermistor; a reference resistor coupled to the other end of the capacitor; sequential charging means coupled to the reference resistor, the thermistor and the capacitor for sequentially charging the capacitor to a predetermined value by the voltage source through the resistor and the thermistor; timing means coupled to the capacitor for measuring the lengths of time required to sequentially charge the capacitor through the reference resistor and the thermistor to obtain a reference charge time and a thermistor charge time, respectively; and computing means for computing the difference between the reference charge time and the thermistor charge time with the difference being divided by the sum of the reference charge time and the thermistor charge time to obtain a value proportional to the temperature to which the thermistor is exposed, such value being substantially independent of leakage of the capacitor.

Claim 9

An apparatus for determining the temperature to which a thermistor is exposed, comprising: a capacitor having one end coupled to a voltage source, and another end coupled to said thermistor; a reference resistor coupled to the other end of the capacitor; sequential charging means coupled to the reference resistor, the thermistor and the capacitor for sequentially charging the capacitor to a predetermined value by the voltage source through the resistor and the thermistor; timing means coupled to the capacitor for measuring the lengths of time required to sequentially charge the capacitor through the reference resistor and the thermistor to obtain a reference charge time and a thermistor charge time, respectively; and computing means for computing the difference between the reference charge time and the thermistor charge time with the difference being divided by the sum of the reference charge time and the thermistor charge time to obtain a value proportional to the temperature to which the thermistor is exposed, such value being substantially independent of leakage of the capacitor.