Speed and fluid flow controller
First Claim
1. In a gas monitoring instrument having an electrically powered motor for driving a pump to bring a sample of gas from a location being tested to a sensor for determining the presence of contaminants in the gas, a motor speed control comprising:
- a) a pulse modulation control and drive operatively connected between a source of voltage and the motor for controlling application of voltage drive pulses to the motor;
b) means operatively associated with the motor for sampling motor back-e.m.f. during intervals between motor drive pulses to provide an output indicative of actual motor speed;
c) means operatively connected to the means for sampling back-e.m.f. to provide a digital signal output containing information on the actual motor speed;
d) a microprocessor connected to the output of the means to provide a digital signal and connected in controlling relation to the pulse modulation control and drive for comparing the actual motor speed to a desired motor speed for controlling the operation of the pulse modulation control; and
e) means for connecting the microprocessor to the means for sampling back-e.m.f. for determining the intervals between modulated motor drive pulses during which motor back-e.m.f. is sampled.
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0 Petitions
Accused Products
Abstract
A system and method for measuring fluid flow rate in a system where fluid is pumped, such as a gas monitoring instrument where gas is pumped from a space such as a room or enclosure through a conduit to a sensor. The flow of gas through a pump is determined by measuring motor back-e.m.f. which is proportional to motor speed. In a system where motor speed is regulated by pulse width modulation of the motor drive voltage, the back-e.m.f. is sampled during intervals between the drive pulses applied to the motor, and in a further aspect the sampling is done at selected, spaced-apart or infrequent intervals such as once for every ten or once for every hundred motor drive pulses. Advantageously, in an instrument that uses a microprocessor and analog-to-digital converter to measure gas-concentration, the same microprocessor and converter can provide the PWM control of the pump, in response to the back-e.m.f. generated by the pump motor between the drive pulses. The microprocessor compares the output of the analog-to-digital converter, corresponding to the back-e.m.f., which in turn corresponds to the pump motor speed, to a set-point value, representative of the desired pump motor speed. The processor then adjusts the PWM to control the pump motor to achieve and maintain the desired speed. As a result, in a gas monitor, the gas-flow rate may be maintained close to a desired gas flow rate regardless of the voltage supplied by the battery or other voltage source, regardless of the degree to which the gas is filtered, and under a wide range of operating conditions.
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Citations
28 Claims
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1. In a gas monitoring instrument having an electrically powered motor for driving a pump to bring a sample of gas from a location being tested to a sensor for determining the presence of contaminants in the gas, a motor speed control comprising:
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a) a pulse modulation control and drive operatively connected between a source of voltage and the motor for controlling application of voltage drive pulses to the motor;
b) means operatively associated with the motor for sampling motor back-e.m.f. during intervals between motor drive pulses to provide an output indicative of actual motor speed;
c) means operatively connected to the means for sampling back-e.m.f. to provide a digital signal output containing information on the actual motor speed;
d) a microprocessor connected to the output of the means to provide a digital signal and connected in controlling relation to the pulse modulation control and drive for comparing the actual motor speed to a desired motor speed for controlling the operation of the pulse modulation control; and
e) means for connecting the microprocessor to the means for sampling back-e.m.f. for determining the intervals between modulated motor drive pulses during which motor back-e.m.f. is sampled. - View Dependent Claims (2, 3)
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4. In a gas monitoring instrument having an electrically powered motor for driving a pump to bring a sample of gas from a location being tested to a sensor for determining the presence of contaminants in the gas:
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a) a pulse modulation control and drive operatively connected between a source of voltage and the motor for controlling application of voltage drive pulses to the motor;
b) means operatively associated with the motor for sampling motor back-e.m.f. during intervals between motor drive pulses to provide an output indicative of actual motor speed which is indicative of pump flow rate; and
c) a control operatively connected to the back-e.m.f. sampling means for determining the intervals between motor drive pulses during which motor back-e.m.f. is sampled to provide an indication of pump flow rate. - View Dependent Claims (5, 6)
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7. A method for monitoring the flow of gas in a gas monitoring instrument wherein a sample of gas is caused to flow from a location being tested to a sensor for determining the presence of contaminants in the gas, the method comprising:
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a) providing pulse modulation of a motor driving a pump which causes the flow of gas in the instrument;
b) sampling motor back-e.m.f. during intervals between motor drive pulses to provide an indication of motor speed to determine the rate of flow of gas through the instrument; and
c) selecting the intervals between motor drive pulses during which motor back-e.m.f. is sampled. - View Dependent Claims (8, 9, 10, 11)
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12. In a system having an electrically powered motor for driving a pump to bring a quantity of fluid from one location to another, a motor speed control comprising:
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a) a pulse modulation control and drive operatively connected between a source of voltage and the motor for controlling application of voltage drive pulses to the motor;
b) means operatively associated with the motor for sampling motor back-e.m.f. during intervals between motor drive pulses to provide an output indicative of actual motor speed;
c) means operatively connected to the means for sampling back-e.m.f. to provide a digital signal output containing information on the actual motor speed;
d) a microprocessor connected to the output of the means to provide a digital signal and connected in controlling relation to the pulse modulation control and drive for comparing the actual motor speed to a desired motor speed for controlling the operation of the pulse modulation control; and
e) means for connecting the microprocessor to the means for sampling back-e.m.f. for determining the intervals between modulated motor drive pulses during which motor back-e.m.f. is sampled. - View Dependent Claims (13, 14)
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15. In a system having an electrically powered motor for driving a pump to bring a quantity of fluid from one location to another:
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a) a pulse modulation control and drive operatively connected between a source of voltage and the motor for controlling application of voltage drive pulses to the motor;
b) means operatively associated with the motor for sampling motor back-e.m.f. during intervals between motor drive pulses to provide an output indicative of actual motor speed which is indicative of pump flow rate; and
c) a control operatively connected to the back-e.m.f. sampling means for determining the intervals between motor drive pulses during which motor back-e.m.f. is sampled to provide an indication of pump flow rate. - View Dependent Claims (16, 17)
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18. A method for monitoring the flow of fluid in a fluid monitoring system wherein a quantity of fluid is caused to flow from one location to another, the method comprising:
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a) providing pulse modulation of a motor driving a pump which causes the flow of gas in the system;
b) sampling motor back-e.m.f. during intervals between motor drive pulses to provide an indication of motor speed to determine the rate of flow of gas through the system; and
c) selecting the intervals between motor drive pulses during which motor back-e.m.f. is sampled. - View Dependent Claims (19, 20, 21, 22)
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23. A motor speed control comprising:
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a) a pulse modulation control and drive for connection between a source of voltage and a motor for controlling application of motor drive pulses to the motor;
b) means operatively associated with the motor for sampling motor back-e.m.f. during intervals between motor drive pulses to provide an output indicative of actual motor speed;
c) means operatively connected to the means for sampling back-e.m.f. to provide a digital signal output containing information on the actual motor speed;
d) a microprocessor connected to the output of the means to provide a digital signal and connected in controlling relation to the pulse modulation control for comparing the actual motor speed to a desired motor speed for controlling the operation of the pulse modulation control; and
e) means for connecting the microprocessor to the means for sampling back-e.m.f. for determining the intervals between modulated motor drive pulses during which motor back-e.m.f. is sampled. - View Dependent Claims (24, 25)
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26. A method for controlling motor speed comprising:
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a) proving pulse modulation control of motor voltage drive pulses applied to the motor;
b) sampling motor back-e.m.f. during intervals between motor drive pulses;
c) comparing the sampled back-e.m.f. indicative of actual motor speed to a signal indicative of desired motor speed for controlling the pulse modulation; and
d) determining the intervals between modulated motor drive pulses during which motor back-e.m.f. is sampled. - View Dependent Claims (27, 28)
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Specification