Built-in test procedure for non-intrusive ultrasonic level sensing

• US 6,615,657 B2
• Filed: 01/04/2001
• Issued: 09/09/2003
• Est. Priority Date: 01/04/2001
• Status: Expired due to Term

• Current Assignee: Rosemount Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rosemount Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Huss, Charles G., Seidel, Greg A., Haugen, Eric D., Hongerholt, Derrick D.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): FRANK, RODNEY T
• Application Number:
  US09/754,795
• Publication Number:
  US 20020083766A1
• Time in Patent Office: 978 Days
• Field of Search: 732/90.R, 732/90.V, 732/92, 732/91, 732/96
• US Class Current: 73/290.00V
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves
• CPC Class Codes: G01F 25/20 of apparatus for measuring liquid level
• CPC Class Codes: G01F 25/24 Testing proper functioning of electronic circuits

Abstract

A built-in test system for an ultrasonic liquid level sensor that includes a transducer assembly having an ultrasonic transducer, and a switch that will be actuated when the ultrasonic transducer is in intimate contact with a surface of a tank in which level is to be determined. Once the switch is actuated to indicate that the ultrasonic transducer is properly coupled to the surface, a test sequence is initiated to determine that the level of ultrasonic transmissions are above a certain desired threshold for a selected period of time, and after which the circuit looks for echoes to determine the depth of the liquid in the tank. Thereafter, the test sequence is repeated for each cycle of level sensing.

Claims

1. An ultrasonic liquid level sensor for determining levels of liquid in a tank during repeating cycles of operation and having a self test circuitry for determining operability of the sensor at a start of each cycle, comprising a sensor assembly including an ultrasonic transducer, and a switch, said sensor assembly adapted to be coupled to the tank in physical contact therewith, and the switch being positioned on the sensor assembly to be operated only when the ultrasonic transducer is in intimate contact with a surface of the tank, the ultrasonic transducer including a circuit having a transmitter for providing pulses of ultrasonic energy from the transducer for a first time period of ultrasonic energy transmission after initiating the pulse of ultrasonic energy at the start of each cycle, a receiver circuit for determining output levels of the ultrasonic energy transmissions during the first time period, a circuit for determining that the receiver circuit output levels are above a selected threshold level for a second selected period of time after the transmitter has initiated the pulses to start a cycle, and a control circuit for turning off the pulse of ultrasonic energy, subsequent to the second period of time, the receiver circuit thereby detecting return pulses from a level of liquid in the tank subsequent to the second period of time during each cycle of operation.

2. The ultrasonic liquid level sensor of claim 1 and a temperature sensor in the transducer assembly positioned to be in contact with the tank when the switch is actuated.

3. An ultrasonic liquid level sensor for determining levels of liquid in a tank, comprising a sensor assembly including an ultrasonic transducer, a circuit for operating the transducer, and a switch coupled to the circuit to provide a signal when the sensor assembly is positioned against a tank surface, said circuit having a transmitter capable of providing a pulse of ultrasonic energy from the ultrasonic transducer in repeating cycles when the switch is closed, and a receiver circuit for determining output levels of transmitted ultrasonic energy, and after a time period subsequent to transmission of a pulse of ultrasonic energy at the start of each cycle, the receiving circuit determining levels of signals of reflected ultrasonic energy from a surface of the liquid in such tank to establish a level of liquid, a timer coupled to the receiver circuit, the receiver circuit providing output signals at levels relative to the transmitted pulses, and indicating when transmitted pulses are above a threshold level at a time before receiving reflected ultrasonic energy signals, and the timer determining that the output signal levels are above the threshold level for a selected timer period after initiation of a transmitted pulse at each of the repeating cycles, and before the receiver circuit receives signals of reflected ultrasonic energy to indicate transducer operability.

4. The ultrasonic liquid level sensor of claim 3, wherein the timer is initiated each time the ultrasonic transducer is energized to transmit pulses.

6. The ultrasonic liquid level sensor of claim 4 wherein the transmitter operates to initiate transmitted pulses at the start of a series of first time periods and the timer is initiated to provide a second time period during each first time period of the transmitter.

5. An ultrasonic liquid level sensor for determining levels of liquid in a tank, comprising a sensor assembly including an ultrasonic transducer, a circuit for operating the transducer, said circuit having a transmitter capable of initiating transmitting pulses of ultrasonic energy from the ultrasonic transducer, each of the pulses terminating after a first transmitter time period subsequent to initiation of pulse transmission, and ultrasonic energy based on the initiated pulses being reflected from a surface of liquid in the tank to the transducer after the first time period, the transducer including a receiver circuit for determining output levels of transmitted ultrasonic energy, and, after the first time period, levels of reflected ultrasonic energy, and a timer coupled to the receiver circuit, the receiver circuit providing output signals at levels which are a function of energy of the transmitted pulses during the first time period, wherein output signal levels above a selected threshold signal level for a selected second time period after initiation of transmitted pulses indicate operability of the ultrasonic transducer.