Method and apparatus for calibration and controlling multiple heaters
First Claim
1. A process of calibrating and running a multiple positive temperature coefficient electrical resistance heater system comprising:
- a. energizing a first heater;
b. sampling the energized heater to determine voltage across the heater and current through the heater;
c. calculating the heater resistance;
d. assigning a temperature to the calculated resistance to establish a calibrated normalized resistance value;
e. repeating steps a-d for each of the heaters;
f. establishing set points for each of the heaters;
g. sampling the first heater for current and voltage;
h. calculating the resistance of said first heater;
i. dividing the calculated resistance of step c by the calculated resistance determined in step h to determine a normalized resistance ratio;
j. comparing the normalized resistance ratio of step "i" to a table of normalized resistance ratios at specific temperatures for the heater material;
k. controlling heater energization based on the comparison of step "j";
l. repeating steps a-k for each of the heaters; and
,m. continuously sampling each of the heaters in sequence and repeating steps g-k at each sampling.
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Accused Products
Abstract
Multiple heaters are calibrated and controlled by a microcomputer, and a multiplexer for this system. The heaters are sequentially sampled and resistance calculated from voltage and current measurements. The operator enters a temperature for the calculated resistance to establish a calibrated resistance value. During run, the computer energizes and samples each heater to calculate its resistance. The calculated resistance if divided by the calibrated resistance to determine a resistance ratio. A look-up table is stored in the computer having resistance ratios for corresponding temperature. The computer compares the calculated ratio to that of the look-up table to determine actual heater temperatures. Based upon heater temperatures, the computer controls energization of the heaters until set points are achieved. Negative temperature coefficient and positive temperature coefficient transistors and semiconductors can be utilized.
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Citations
17 Claims
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1. A process of calibrating and running a multiple positive temperature coefficient electrical resistance heater system comprising:
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a. energizing a first heater; b. sampling the energized heater to determine voltage across the heater and current through the heater; c. calculating the heater resistance; d. assigning a temperature to the calculated resistance to establish a calibrated normalized resistance value; e. repeating steps a-d for each of the heaters; f. establishing set points for each of the heaters; g. sampling the first heater for current and voltage; h. calculating the resistance of said first heater; i. dividing the calculated resistance of step c by the calculated resistance determined in step h to determine a normalized resistance ratio; j. comparing the normalized resistance ratio of step "i" to a table of normalized resistance ratios at specific temperatures for the heater material; k. controlling heater energization based on the comparison of step "j"; l. repeating steps a-k for each of the heaters; and
,m. continuously sampling each of the heaters in sequence and repeating steps g-k at each sampling. - View Dependent Claims (2, 3, 4, 5)
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6. A process of calibrating and running a multiple negative temperature coefficient electrical resistance heater system and comprising:
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a. energizing a first heater; b. sampling the energized heater to determine voltage across the heater and current through the heater; c. calculating the heater resistance; d. assigning a temperature to the calculated resistance to establish a calibrated normalized resistance value; e. repeating steps a-d for each of the heaters; f. establishing set points for each of the heaters; g. sampling the first heater for current and voltage; h. calculating the resistance of said first heater; i. dividing the calculated resistance of step c by the calculated resistance determined in step h to determine a normalized resistance ratio; j. comparing the normalized resistance ratio of step "i" to a table of normalized resistance ratios at specific temperatures for the heater material; k. controlling heater energization based on the comparison of step "j"; l. repeating steps a-k for each of the heaters; and
,m. continuously sampling each of the heaters in sequence and repeating steps g-k at each sampling. - View Dependent Claims (7, 8, 9, 10)
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11. Apparatus for calibrating and controlling operation of multiple positive temperature coefficient electrical resistance heaters having power supply means and switch means for controlling the application of power to each of said heaters comprising:
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a. means for detecting current through and voltage across each of the heaters; b. a multiplexer coupled to said means for detecting; c. means including converter means coupled to said multiplexer; d. a programmed microcomputer having memory means and calculating means; e. means coupling said microcomputer to said multiplexer, converter means, and detecting means for control thereof; f. means connecting said microcomputer to said switch means for control thereof; g. a look up table, having data relating temperature to normalized resistance rations for the specific material of the heaters, stored in said memory means; h. keyboard means connected to said microcomputer;
wherein,i. when power is applied to the system, the microcomputer through control of the switch means, detector means, multiplexer means, and converter means calculates normalized resistance ratios for each of the heaters and compares such ratios to the look-up table ratios for control of heater energization through said switch means based on said comparison. - View Dependent Claims (12)
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13. Apparatus for calibrating and controlling operation of multiple negative temperature coefficient electrical resistance heaters having power supply means and switch means for controlling the application of power to each of said heaters comprising:
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a. means for detecting current through and voltage across each of the heaters; b. a multiplexer coupled to said means for detecting; c. means including converter means coupled to said multiplexer; d. a programmed microcomputer having memory means and calculating means; e. means coupling said microcomputer to said multiplexer, converter means, and detecting means for control thereof; f. means connecting said microcomputer to said switch means for control thereof; g. a look up table, having data relating temperature to normalized resistance rations for the specific material of the heaters, stored in said memory means; h. keyboard means connected to said microcomputer;
wherein,i. when power is applied to the system, the microcomputer through control of the switch means, detector means, multiplexer means, and converter means calculates normalized resistance ratios for each of the heaters and compares such ratios to the look-up table ratios for control of heater energization through said switch means based on said comparison. - View Dependent Claims (14, 15, 16, 17)
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Specification