Patent Description:
Analog circuits are widely used in process control systems. Measurements from analog circuits are often a critical part of a process control system. In some process control environments, analog circuits are exposed to radiation, which can degrade the semiconductor devices used to implement the circuits to the point of failure. As the cumulative exposure to radiation increases, an output of an analog circuit may drift and/or a frequency response of the circuit degrades until the process control system can no longer compensate for the errors resulting from the degradation. Detection of analog circuit degradation before the degradation adversely affects the measurements from the analog circuit enables an operator to take action to keep the process under control. For example, if degradation of an analog circuit associated with a sensor due to radiation is detected, a positioner or controller that uses the sensor for control feedback may switch to a different control mode and ignore the feedback from the analog circuit to which the sensor is coupled. Document <CIT> describes known method and apparatus for radiation effects detection. Known means for radiation detection are also described in document <CIT>. A hybrid semiconductor type radiation detector is described in the document <CIT>. Document <CIT> discloses an integrated circuit with automatic total ionizing dose exposure deactivation. Document <CIT> describes apparatus and methods for fluid processing and flow control.

The invention relates to a method according to claim <NUM>.

The invention relates to an apparatus according to claim <NUM>.

Another example apparatus that does not form part of the present invention includes an analog circuit having a first integrated circuit, a reference circuit having a second integrated circuit identical to the first integrated circuit, where the reference circuit provides a feedback signal, the feedback signal indicative of degradation of the reference circuit and the analog circuit, and a process control device to monitor the feedback signal from the reference circuit.

The example apparatus and methods described herein may be implemented to predict and detect degradation and failure of semiconductor devices within analog circuits due to radiation exposure. The example apparatus and methods may be used in a process control environment or in any other environment.

Some examples described herein include a semiconductor device, such as an operational amplifier, having a known degradation characteristic due to radiation exposure. As the cumulative amount of radiation exposure (e.g., radiation dose) increases, the current consumption of the semiconductor device changes in a predictable way. This change may follow a degradation curve associated with the semiconductor. In some examples, the rate of degradation is variable and the total radiation dose to which the semiconductor has been exposed affects how quickly the measured current of the semiconductor decreases.

In an example described herein, a semiconductor device is coupled to a positioner that measures a current supplied to the semiconductor device and, using the degradation curve, correlates the measured current with a radiation dose. The positioner compares the radiation dose to a predetermined threshold based on the degradation curve of the semiconductor to detect when the radiation dose reaches a radiation dose threshold. To enable the operation of the example apparatus, the positioner may include a memory to store the data and the degradation curve, a communication interface to receive data and send alarms, and a processor to compare the measured supply current to the degradation curve.

The radiation dose threshold is defined by the degradation curve and corresponds to an amount of radiation exposure that causes the circuit being monitored to degrade or fail. When the radiation dose reaches the radiation dose threshold, the positioner may send an alert to an operator workstation indicating that a circuit (e.g., an analog circuit associated with a feedback sensor) coupled to the positioner may be degrading or is close to failure. Additionally, if the radiation dose is within a range of the radiation dose threshold, degradation or failure of the circuit is likely to occur and the processor sends an alarm to the operator workstation.

<FIG> is a block diagram of an example apparatus <NUM> that may be implemented to detect degradation or failure of a circuit due to radiation exposure. The example apparatus <NUM> includes an example semiconductor device <NUM> that acts as a radiation exposure monitor that indicates an amount of radiation (e.g., a radiation dose) to which the example apparatus <NUM> has been exposed. The example semiconductor device <NUM> may be implemented as an operational amplifier (as shown in <FIG>), a transistor, a diode or any other electrical circuit component with a known degradation curve due to radiation exposure. A supply current of the semiconductor device <NUM> may be measured by a positioner <NUM> (which in the presently claimed invention is a process control device) coupled to the semiconductor device <NUM>. The known degradation curve associated with the semiconductor device <NUM> correlates a measured current of the semiconductor device <NUM> with an amount of radiation to which the semiconductor device <NUM> has been exposed. As the amount of radiation exposure increases, the current of the semiconductor device <NUM> changes in a predictable way as described, for example, by a degradation curve associated with the semiconductor device <NUM>. For example, the supply current of the semiconductor device <NUM> may decrease due to the increase of radiation exposure.

The semiconductor device <NUM> may be selected based on the analog circuit used in the example apparatus <NUM>. The analog circuit <NUM> (e.g., a process control circuit) may be used to perform a variety of functions in a process control system, such as measuring parameters, operating process control components, and/or communicating data to the positioner <NUM>. The semiconductor device <NUM> may be selected in accordance with the amount of radiation the analog circuit <NUM> can withstand. For example, the semiconductor device <NUM> may be selected such that the radiation dose threshold defined by the degradation curve corresponds to an amount of radiation the analog circuit <NUM> of the example apparatus <NUM> can withstand prior to degradation or failure. Thus, in one such example, if the analog circuit <NUM> associated with the semiconductor device <NUM> can withstand <NUM>,<NUM> radiation absorbed doses (i.e., <NUM> krads) of radiation exposure, the selected semiconductor device <NUM> may be a radiation hardened operational amplifier that has been tested for performance up to <NUM> krads of radiation exposure. In some examples, the semiconductor device <NUM> may be selected such that the semiconductor device <NUM> is operative to warn the operator of the potential circuit failure by a reaching a threshold current defined by the degradation curve, but the semiconductor device <NUM> remains operable throughout operation of the example apparatus <NUM>. In other examples, the analog circuit <NUM> may be tolerant of a different amount of radiation exposure and, thus, the selected semiconductor device <NUM> may be able to withstand a different amount of radiation.

In some examples, redundant or multiple semiconductor devices <NUM> may be used to ensure the detection of radiation exposure is accurate and not a false detection in response to a degradation or failure of the semiconductor device <NUM> due to another reason such as, for example, a voltage surge or spike. The current measurements from the multiple semiconductor devices <NUM> may be polled or compared to detect if one of the semiconductor devices <NUM> may be failing in response to something other than radiation exposure. In some examples, all of the semiconductor devices <NUM> are the same type and the current measurements of the semiconductor devices <NUM> may be averaged prior to comparison with the degradation curve associated with the semiconductor devices <NUM>. In other examples, an outlying current measurement may be determined while comparing the measurements from the multiple semiconductor devices <NUM> and, if an outlying current measurement exists, that measurement may be disregarded. Alternatively, each of the semiconductor devices <NUM> may be rated to withstand a different radiation dose and compared to corresponding degradation curves.

The semiconductor device <NUM> may be implemented in the example apparatus <NUM> solely to act as a radiation exposure detection device for the example apparatus <NUM>, including the analog circuit <NUM>. In other examples, the semiconductor device <NUM>, in addition to acting as a radiation exposure monitor, may also function in a manner consistent with the intended application of the semiconductor device <NUM>. For example, if the semiconductor device <NUM> is an operational amplifier, then the semiconductor device <NUM> may also perform an amplification function.

The semiconductor device <NUM> is coupled to the example positioner <NUM>, which may be a digital valve controller similar to those used in process control systems. However, in some examples, other types of positioners <NUM>, which are configured to control a position of a valve, may be used instead. In some examples, the semiconductor device <NUM> may be integrated within the positioner <NUM>. In other examples, the semiconductor device <NUM> is separate from the positioner <NUM> and the positioner <NUM> may monitor the semiconductor device <NUM> remotely. The positioner <NUM> may also be operatively coupled to the analog circuit <NUM> and an operator workstation <NUM>. The positioner <NUM> can send alerts and alarms to the operator workstation <NUM> and receive messages, data and commands from the operator workstation <NUM>. The operator workstation <NUM> may be a computer, a handheld device, or any other device capable of sending and receiving messages, data and commands. A more detailed depiction of the example positioner <NUM> described herein is shown and described in connection with <FIG>.

As depicted in <FIG>, the example positioner <NUM> includes a memory <NUM>, a communication interface <NUM>, and a processor <NUM>. The memory <NUM> may be any type of tangible computer readable storage device or storage disk. The memory <NUM> is used to store, temporarily or permanently, any data that is used to determine the radiation dose to which the example apparatus <NUM> is exposed. For example, the degradation curve associated with the semiconductor device <NUM>, any measurements associated with the semiconductor device <NUM> such as, for example, the measured current, and any values determined or used during the process of detecting the radiation dose to which the example apparatus <NUM> is exposed.

The communication interface <NUM> is operative to receive the current from the semiconductor device <NUM>, which is measured by the processor <NUM>, and send alarms to the operator workstation <NUM> (<FIG>). Other data relating to an operation or status of the example apparatus <NUM>, such as process control data and commands, may also be communicated through the communication interface <NUM>.

The processor <NUM> monitors and measures the total current flowing through the semiconductor device <NUM> via a signal monitor <NUM>. Once the current is measured, the processor <NUM> accesses the degradation curve from the memory <NUM> and compares the measured current to the degradation curve to correlate the measured current with the radiation dose via a current and radiation correlator <NUM>. The processor <NUM> may also determine the radiation dose threshold using the degradation curve. The radiation dose threshold may be associated with an amount of radiation exposure that causes the analog circuit <NUM> to degrade to a level of performance that is deemed unacceptable. The radiation dose threshold may correspond to a point on the degradation curve at which the radiation dose is high enough to render the semiconductor device <NUM> device inoperable for its purpose. The processor <NUM> uses the determined radiation dose of the example apparatus <NUM> and compares that amount to the radiation dose threshold to determine if the radiation dose has reached the radiation dose threshold via a radiation level comparator <NUM>. If the radiation dose has reached the radiation dose threshold, an alarm manager <NUM> of the processor <NUM> may send an alarm or alert to the operator workstation <NUM> operatively coupled to the positioner <NUM>, alerting an operator of the possible degradation or failure of the analog circuit <NUM>. If the radiation dose is within a range of the radiation dose threshold, degradation or failure of the analog circuit is likely to occur and the alarm manager <NUM> sends an alarm to the operator workstation <NUM> indicating the likelihood of degradation or failure of the analog circuit <NUM>. Sending an alert to the operator workstation <NUM> indicating potential failure of the circuit <NUM> enables an operator to take action to prevent the failure of the analog circuit <NUM> from affecting the process control system. For example, in response to receiving the alert, the operator may change the operating mode of the process control system. In other examples, the operator may replace or repair the components of the affected circuit <NUM>.

<FIG> depicts an example radiation degradation curve <NUM> that may be associated with the semiconductor device <NUM> of the example apparatus <NUM> described herein. The example degradation curve <NUM> of <FIG> correlates a supply current <NUM> of the semiconductor device <NUM> with a total dose <NUM> of radiation exposure. In this example, the degradation curve <NUM> is associated with a radiation hardened micropower dual operational amplifier.

The example degradation curve <NUM> has an initial current <NUM> when the total dose <NUM> is small (e.g., less than <NUM> krads). The supply current <NUM> begins to decrease when the total dose <NUM> reaches a deterioration dose <NUM>. The supply current <NUM> continues to decrease until the supply current <NUM> is no longer sufficient to operate the semiconductor device <NUM>. The total dose <NUM> when the supply current <NUM> becomes inoperable is the degradation point <NUM> of the semiconductor device <NUM>, and may also be the radiation dose threshold defined by the degradation curve <NUM>. In some examples, another point of the degradation curve <NUM> may be selected to be the radiation dose threshold. The example degradation curve <NUM> of <FIG> depicts curves for two different supply voltages, but other degradation curves may exist.

<FIG> is a block diagram of another example apparatus <NUM> that does not form part of the present invention and that may be implemented to detect degradation or failure of a circuit due to radiation exposure. The example apparatus <NUM> of <FIG> may be implemented if a semiconductor device having a known degradation due to radiation is not available or the degradation of an available semiconductor devices does not correspond with the degradation of an analog circuit <NUM>. The analog circuit <NUM> may perform one or more primary functions of the apparatus <NUM>. In some examples, the primary function performed by the analog circuit <NUM> may include amplifying a bridge resistance of a Hall Effect sensor circuit.

The example apparatus <NUM> includes a reference circuit <NUM> that may be used to detect degradation due to radiation. The reference circuit <NUM> may be similar to the analog circuit <NUM> and, thus, may contain similar and/or identical components. For example, the reference circuit may contain at least one integrated circuit (e.g., an operational amplifier) identical to at least one integrated circuit of the analog circuit. In some examples, the reference circuit <NUM> may be implemented to provide a feedback signal (e.g., a current signal or a voltage signal) to the positioner <NUM> via the communication interface <NUM> to monitor the reference circuit <NUM> and/or the analog circuit <NUM> for degradation due to radiation. In some examples, the signal from the reference circuit <NUM> to the positioner <NUM> may include an amplified signal from a fixed resistive bridge. Thus, the signal from the reference circuit <NUM> is substantially affected only by degradation due to radiation and not by the fluctuations of the parameter being measured by the analog circuit <NUM>. As a result, the signal to the positioner <NUM> from the reference circuit <NUM> indicates when the reference circuit <NUM> and, thus, the analog circuit <NUM>, may be experiencing degradation due to radiation. Specifically, the reference circuit <NUM> is to provide a fixed signal output (e.g., a constant voltage or current) due to the fixed bridge resistance to which it is coupled. If the reference circuit <NUM> is exposed to radiation, an operational amplifier, for example, within the reference circuit <NUM> may degrade, whereas the bridge resistance to which the reference circuit <NUM> is coupled will not be affected in any meaningful way by the radiation. However, the degradation of the operational amplifier causes a change in the signal output of the reference circuit, thereby indicating an amount of degradation.

If the signal monitor <NUM> of the positioner <NUM> detects that the signal from the reference circuit <NUM> has degraded, the alarm manager <NUM> of the positioner <NUM> can send alerts and alarms to the operator workstation <NUM> and receive messages, data and commands from the operator workstation <NUM>. To detect that the signal from the reference circuit has degraded, the positioner may compare a variance of the feedback signal from the reference circuit <NUM> to a variation threshold. A change in the feedback signal beyond the variation threshold may indicate that the analog circuit <NUM> and/or the reference circuit <NUM> is experiencing degradation. The variation threshold may be selected by the operator. The variance of the feedback signal may be determined by comparing an initial value of the feedback signal to a current value of the feedback signal.

The example positioner <NUM> and/or processor <NUM> of <FIG> and <FIG> may be implemented by any combination of hardware, software and/or firmware. Thus, for example, the example positioner <NUM> and/or processor <NUM> could be implemented by one or more analog or digital circuit(s), logic circuits, programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)). When reading any of the apparatus or method claims of this patent to cover a purely software and/or firmware implementation, the example positioner <NUM> and/or processor <NUM> are hereby expressly defined to include a tangible computer readable storage device or storage disk such as a memory, a digital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc. storing the software and/or firmware. Further still, the example positioner <NUM> and/or processor <NUM> of <FIG> and <FIG> may include one or more elements, processes and/or devices and/or may include more than one of any or all of the elements, processes and devices.

Additionally, the example positioner <NUM> and/or processor <NUM> of <FIG> and <FIG> may communicate with one or more of the components (e.g., the semiconductor device <NUM>, the analog circuit <NUM> and/or <NUM>, the operator workstation <NUM>, the reference circuit <NUM>, etc.) using any type of wired connection (e.g., a databus, a USB connection, etc.) or a wireless communication mechanism (e.g., radio frequency, infrared, etc.) using any past, present or future communication protocol (e.g., Bluetooth, USB <NUM>, USB <NUM>, etc.). Further, one or more components of <FIG> and <FIG> may communicate with each other using such wired connection or wireless communication mechanisms.

<FIG> depicts an example method <NUM> that may be implemented with the example apparatus <NUM> described herein. The example method <NUM> begins with the signal monitor <NUM> of the processor <NUM> monitoring and/or measuring the current of the semiconductor device <NUM> (block <NUM>). The current and radiation correlator <NUM> of the processor <NUM> uses the degradation curve <NUM> to correlate the measured current with the radiation dose (block <NUM>). The radiation level comparator <NUM> compares the radiation dose to the radiation dose threshold (block <NUM>). The processor <NUM> then determines if the radiation dose has reached the radiation dose threshold (block <NUM>). If the radiation dose has reached the radiation dose threshold, the alarm manager <NUM> sends an alarm or alert to the operator workstation <NUM> to alert the operator of the degradation or failure of the analog circuit <NUM> (block <NUM>). If the radiation dose has not reached the radiation dose threshold, the processor <NUM> determines if the radiation dose is within a range of the radiation dose threshold (block <NUM>). If the radiation dose is within a range (e.g., within <NUM> krads) of the radiation dose threshold, the alarm manager <NUM> sends an alert or alarm to the operator workstation <NUM> (block <NUM>). If the radiation dose is not within the range of the radiation dose threshold, the signal monitor <NUM> may continue monitoring the current of the semiconductor device <NUM> (block <NUM>) or the process of detecting circuit failure due to radiation may conclude.

<FIG> depicts an example method <NUM> that may be implemented with the example apparatus <NUM> described herein. The example method <NUM> begins with the signal monitor <NUM> of the processor <NUM> of the positioner <NUM> monitoring and/or measuring the signal output by the reference circuit <NUM> (block <NUM>). The processor <NUM> then determines if the signal output by the reference circuit <NUM> has degraded due to radiation by comparing a variance of the feedback signal from the reference circuit <NUM> to a variation threshold (block <NUM>). If the signal output by the reference circuit <NUM> has degraded due to radiation, the alarm manager <NUM> sends an alarm or alert to the operator workstation <NUM> to alert the operator of the degradation or failure of the analog circuit <NUM> (block <NUM>). If the signal of the reference circuit has not been affected due to radiation exposure, the signal monitor <NUM> may continue monitoring the signal output by the reference circuit <NUM> (block <NUM>) or the process of detecting circuit failure due to radiation may conclude.

In the described examples, at least a portion of the example methods <NUM> and <NUM> represented by the flowcharts in <FIG> and <FIG> may be implemented using machine readable instructions that comprise a program for execution by a processor such as the processor <NUM> shown in the example processor platform <NUM> discussed below in connection with <FIG>. The program may be embodied in software stored on a tangible computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a digital versatile disk (DVD), a Blu-ray disk, or a memory associated with the processor <NUM>, but the entire program and/or parts thereof could alternatively be executed by a device other than the processor <NUM> and/or embodied in firmware or dedicated hardware. Further, although the example program is described with reference to the flowcharts illustrated in <FIG> and <FIG>, many other methods of implementing the example apparatus described herein may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined.

As mentioned above, at least a portion of the example methods <NUM> and <NUM> of <FIG> and <FIG> may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a tangible computer readable storage medium such as a hard disk drive, a flash memory, a read-only memory (ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, a random-access memory (RAM) and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term tangible computer readable storage medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, "tangible computer readable storage medium" and "tangible machine readable storage medium" are used interchangeably. Additionally or alternatively, the example method of <FIG> may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a non-transitory computer and/or machine readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media.

<FIG> is a block diagram of an example processor platform <NUM> capable of executing instructions to implement at least a portion of the methods of <FIG> and <FIG>. The processor platform <NUM> can be, for example, a server, a personal computer, a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad™), a personal digital assistant (PDA), an Internet appliance or any other type of computing device.

The processor <NUM> may correspond to the processor <NUM> and/or may include the signal monitor <NUM>, the current and radiation correlator <NUM>, the radiation level comparator <NUM> and the alarm manager <NUM>.

The input device(s) <NUM> permit(s) a user to enter data and commands into the processor <NUM>. The input device(s) <NUM> can be implemented by, for example, an audio sensor, a microphone, a camera (still or video), a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, isopoint and/or a voice recognition system.

The output devices <NUM> can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display, a cathode ray tube display (CRT), a touchscreen, a tactile output device, a printer and/or speakers). The interface circuit <NUM> of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor.

The mass storage device may additionally include the memory <NUM>.

Claim 1:
An apparatus comprising:
a semiconductor device (<NUM>) in an analog circuit (<NUM>) for a process control system, the semiconductor device (<NUM>) having a known degradation in response to radiation exposure; and
a process control device (<NUM>) configured to control a position of a valve within the process control system, the process control device coupled to the semiconductor device (<NUM>) and including a memory (<NUM>), a communication interface (<NUM>), and a processor (<NUM>), the process control device (<NUM>) being configured to:
monitor, via the processor (<NUM>), a supply current of the semiconductor device (<NUM>);
correlate, via the processor (<NUM>), the supply current with a cumulative amount of radiation exposure;
compare, via the processor (<NUM>), the amount of radiation exposure to a radiation dose threshold, the radiation dose threshold derived from the known degradation and corresponding to an amount of radiation at which the semiconductor device (<NUM>) degrades; and
send, via the communication interface (<NUM>), an alert to an operator workstation (<NUM>) when degradation is indicated based on the comparison to prevent the failure of the analog circuit (<NUM>) from affecting the process control system.