U.S. patent application number 09/758051 was filed with the patent office on 2001-09-27 for transient voltage recorder.
Invention is credited to Medelius, Pedro J., Simpson, Howard J..
Application Number | 20010024115 09/758051 |
Document ID | / |
Family ID | 26870949 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010024115 |
Kind Code |
A1 |
Medelius, Pedro J. ; et
al. |
September 27, 2001 |
Transient voltage recorder
Abstract
A voltage transient recorder can detect lightning induced
transient voltages. The recorder detects a lightning induced
transient voltage and adjusts input amplifiers to accurately record
transient voltage magnitudes. The recorder stores voltage data from
numerous monitored channels, or devices. The data is time stamped
and can be output in real time, or stored for later retrieval. The
transient recorder, in one embodiment, includes an
analog-to-digital converter and a voltage threshold detector. When
an input voltage exceeds a pre-determined voltage threshold, the
recorder stores the incoming voltage magnitude and time of arrival.
The recorder also determines if its input amplifier circuits clip
the incoming signal or if the incoming signal is too low. If the
input data is clipped or too low, the recorder adjusts the gain of
the amplifier circuits to accurately acquire subsequent components
of the lightning induced transients.
Inventors: |
Medelius, Pedro J.; (Merritt
Island, FL) ; Simpson, Howard J.; (Eustis,
FL) |
Correspondence
Address: |
NASA, John F. Kennedy Space Center
Mail Code: CC-A
Office of the Chief Counsel
Kennedy Space Center
FL
32899
US
|
Family ID: |
26870949 |
Appl. No.: |
09/758051 |
Filed: |
January 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60175168 |
Jan 7, 2000 |
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Current U.S.
Class: |
324/72 |
Current CPC
Class: |
G01R 19/0053 20130101;
G01R 29/0892 20130101 |
Class at
Publication: |
324/72 |
International
Class: |
G01R 031/02 |
Claims
What is claimed is:
1. A transient voltage recorder comprising: an input to receive a
voltage signal; an amplifier having a gain coupled to the input; an
amplifier gain adjust circuit coupled to adjust the gain of the
amplifier; and a sample and hold circuit coupled to the
amplifier.
2. The transient voltage recorder of claim 1 wherein the sample and
hold circuit comprises: an analog-to-digital converter coupled to
the amplifier; and a controller coupled to the analog-to-digital
converter and the amplifier gain adjust circuit, wherein the
controller determines if an output from the amplifier is clipped or
too low and controls the amplifier gain adjust circuit to adjust
the gain of the amplifier.
3. The transient voltage recorder of claim 2 further comprises: a
non-volatile memory device; and a time circuit, wherein the
controller stores output from the analog-to-digital converter and a
corresponding time of arrival, determined by the time circuit, in
the nonvolatile memory device.
4. The transient voltage recorder of claim 1 wherein the sample and
hold circuit comprises: an analog-to-digital converter coupled to
the amplifier; a voltage threshold circuit; and a controller
coupled to the analog-to-digital converter, the voltage threshold
circuit and the amplifier gain adjust circuit, wherein the
controller monitors an output of the amplifier in response to the
voltage threshold circuit and determines if the output from the
amplifier is clipped or too low, the controller further controls
the amplifier gain adjust circuit to adjust the gain of the
amplifier.
5. The transient voltage recorder of claim 4 further comprises: a
memory device; and a time circuit, wherein the controller stores
output from the analog-to-digital converter and a corresponding
time of arrival, determined by the time circuit, in the memory
device.
6. The transient voltage recorder of claim 4 wherein the recorder
is rearmed within a few microseconds of receiving a voltage
signal.
7. The transient voltage recorder of claim 4 wherein the voltage
signal is sampled at least 20 mega-samples per second.
8. The transient voltage recorder as claimed in claim 4, wherein
the transient voltage recorded is induced by lightning.
9. The voltage transient recorder as claimed in claim 5,
comprising: a plurality of input amplifiers each coupled to receive
one of a plurality of input voltage signals; the amplifier gain
adjust circuit is coupled to adjust the gain of the plurality of
amplifiers; the analog-to-digital converter is coupled to outputs
of the plurality of amplifiers; the voltage threshold circuit
coupled to the outputs of the plurality of amplifiers; and the
controller monitors the outputs of the plurality of amplifiers in
response to the voltage threshold circuit and determines if the
outputs of the plurality of amplifiers are magnitude clipped or too
low.
10. A method of recording a transient voltage comprising:
monitoring an input voltage signal; detecting when the input
voltage signal exceeds a pre-determined threshold voltage level;
determining if an input amplifier gain is too large or too small
for the input voltage signal; and reducing or increasing the gain
of the input amplifier to capture the input voltage signal.
11. The method of claim 10 wherein monitoring the input voltage
comprises: converting the input voltage signal to digital data; and
comparing the input voltage signal to a pre-determined threshold
voltage level.
12. The method of claim 11 wherein determining if an input
amplifier gain is too large comprises: comparing successive output
samples of the digital data; and determining that an output of the
input amplifier is clipped if the successive output samples of the
digital data are substantially the same.
13. The method of claim 10 further comprises storing the input
voltage signal and a corresponding time of arrival.
14. The method of claim 10 wherein the recorder is rearmed within a
few microseconds of receiving a voltage signal.
15. The method of claim 10 wherein the voltage signal is sampled at
least 10 mega-samples per second.
16. The method of claim 10, wherein the transient voltage recorded
is induced by lightning.
17. A method of recording a transient voltage comprising:
amplifying an analog input voltage signal with an input amplifier
circuit; comparing the input voltage signal to a pre-determined
threshold voltage level, and detecting when the amplified analog
input voltage signal exceeds the pre-determined threshold voltage
level; converting the analog amplified input voltage signal to
digital data; comparing successive samples of the digital data; and
determining that an output of the input amplifier circuit is
clipped if the successive output samples of the digital data are
substantially the same.
18. The method of claim 17 further comprising: reducing the gain of
the input amplifier circuit to capture the input voltage
signal.
19. The method of claim 17 further comprises storing the input
voltage signal and a corresponding time of arrival.
Description
[0001] This patent application is based on provisionally filed
patent application Ser. No. 60/175,168 entitled "High Speed
Transient Voltage Recording System" by Pedro J. Medelius et al.
filed Jan. 7, 2000. The invention described herein was made in the
performance of work under a NASA contract and is subject to the
provisions of Section 305 of the National Aeronautics and Space Act
of 1958, as amended, Public Law 85-568 (72 Stat. 435; 42 U.S.C.
.sctn.2457).
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to voltage recorders
and in particular the present invention relates to transient
voltage recorders. Voltage transients caused by atmospheric
disturbances are often present in power and communication lines.
These transients are especially noticeable following a nearby
lightning strike. Although most electronic equipment has some form
of transient protection, some limitations exist on maximum
sustainable transient levels. This limitation is determined by both
the amplitude and duration that the equipment can withstand before
permanent damage occurs. Electronic components and equipment can
have an immediate, easy to detect failure when they are subjected
to voltages larger than their maximum rated values. Obvious
failures include short-circuited components, open components, or
non-functional components. Transient voltages can also alter
characteristics of an electronic component without obvious sign of
failure. Unless there is a way to determine that transient voltages
were present, such anomalies can remain undetected and eventually
lead to premature failure of a component.
[0003] Transient voltage recorders have been used for many years to
monitor voltages and currents on cables. Common sources of
transient voltages include large electronic motors, switching of
power equipment, induced voltages from nearby lightning strikes,
and direct lightning strikes. Transients generated by sources other
than lightning tend to have frequency components well below one
megahertz, which most commercial transient recorders can detect. On
the other hand, recent research has shown that lightning induced
transients contain voltage peaks that rise in a small fraction of a
microsecond and contain frequencies exceeding tens of megahertz.
Commercially available recorders cannot measure these fast peaks.
Thus, incorrect indications of the magnitude of the peak value of
transients are provided.
[0004] For the reasons stated above, and for other reasons stated
below which will become apparent to those skilled in the art upon
reading and understanding the present specification, there is a
need in the art for a transient voltage recorder that can
accurately characterize lightning induced voltage transients.
SUMMARY OF THE INVENTION
[0005] The above-mentioned problems with voltage transient
recorders and other problems are addressed by the present invention
and will be understood by reading and studying the following
specification.
[0006] In one embodiment, a transient voltage recorder comprises an
input to receive a voltage signal, an amplifier coupled to the
input, an amplifier gain adjust circuit coupled to adjust a gain of
the amplifier, and a sample and hold circuit coupled to the
amplifier.
[0007] In another embodiment, a transient voltage recorder
comprises an input to receive a voltage signal, an amplifier
coupled to the input, an amplifier gain adjust circuit coupled to
adjust a gain of the amplifier and an analog-to-digital converter
coupled to the amplifier. The transient voltage recorder includes a
voltage threshold circuit, and a controller coupled to the
analog-to-digital converter, the voltage threshold circuit and the
amplifier gain adjust circuit. The controller monitors an output of
the amplifier in response to the voltage threshold circuit and
determines if the output from the amplifier is clipped or is too
low. The controller further controls the amplifier gain adjust
circuit to adjust the gain of the amplifier.
[0008] In yet another embodiment, a transient voltage recorder
comprises a plurality of input amplifiers each coupled to receive
one of a plurality of input voltage signals, and an amplifier gain
adjust circuit coupled to adjust a gain of the plurality of
amplifiers. An analog-to-digital converter is coupled to outputs of
the plurality of amplifiers. Further, a voltage threshold circuit
is coupled to the outputs of the plurality of amplifiers. The
voltage transient recorder further comprises a non-volatile memory
device, a time circuit, and a controller coupled to the
analog-to-digital converter, the voltage threshold circuit, the
non-volatile memory device and the amplifier gain adjust circuit.
The controller monitors the outputs of the plurality of amplifiers
in response to the voltage threshold circuit and determines if the
outputs of the plurality of amplifiers are magnitude clipped or
have a low signal. The controller further controls the amplifier
gain adjust circuit to adjust the gain of the amplifier.
[0009] A method of recording a transient voltage is provided that
comprises monitoring an input voltage signal, detecting when the
input voltage signal exceeds a pre-determined threshold voltage
level, determining if an input amplifier gain it too large or too
small for the input voltage signal, and reducing or increasing the
gain of the input amplifier to capture the input voltage
signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a block diagram of a transient voltage detector
system of an embodiment of the present invention; and
[0011] FIG. 2 is a more detailed diagram of a voltage transient
detector system of an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0012] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings, which
form a part hereof, and in which is shown by way of illustration
specific preferred embodiments in which the inventions may be
practiced. These embodiments are described in sufficient detail to
enable those skilled in the art to practice the invention, and it
is to be understood that other embodiments may be utilized and that
logical, mechanical and electrical changes may be made without
departing from the spirit and scope of the present invention. The
following detailed description is, therefore, not to be taken in a
limiting sense, and the scope of the present invention is defined
only by the claims.
[0013] Referring to FIG. 1, a block diagram of a transient voltage
monitoring system of one embodiment of the present invention is
illustrated. This embodiment of the system includes a number of
electronic sites to be monitored, however any number of sites may
be used, including one site. The sites can be remotely located,
closely located to each other, or collocated. In the illustrated
system, four sites 100, 102, 104 and 106 are monitored for
transient voltages. These sites can be any type of electronic
circuit, or device, that are susceptible to voltage transients. The
term site is used herein to generally refer to electronic
equipment, electronic signal lines, interconnects, voltage nodes
and the like. A transient voltage recorder 110 is coupled to the
sites and is capable of detecting lightning induced as well as any
other types of voltage transients. The detected transient magnitude
and time of detection are stored in a memory 114. The time is
accurately determined through an external time device 112.
Alternately, the time can be provided through an internal circuit.
Output from the transient recorder can be remotely monitored to
determine if transients have been recorded.
[0014] A more detailed illustration of one embodiment of a
transient voltage recorder of the present invention is provided in
FIG. 2. The recorder includes several channel inputs coupled to
amplifier circuits 120, 122, 124 and 126. The outputs of the
amplifiers are coupled to sample and hold circuitry. In one
embodiment, the sample and hold circuitry includes an
analog-to-digital converter 130 to provide digital transient
magnitude data. The analog-to-digital converter can be a 12-bit
analog-to-digital converter or any other equivalent device. The
digital output is routed through FIFO buffer 132 to a
micro-controller 140. The buffer can store data from each channel
that is monitored. As explained below, buffer block 132 can include
multiple buffer circuits of different bandwidth and depth. The
sample time of the FIFO is controlled by the micro-controller and
can be externally adjusted. The micro-controller can also store the
digital output in memory 114, which for example may be non-volatile
memory. The micro-controller is capable of storing a time-stamp
(time of arrival) with the digital data. A time-stamp circuit 112
may use output signals from a clock 146 and/or an Inter-Range
Instrumentation Group (IRIG-B) decoder 148. The IRIG decoder
decodes time from a satellite system. Accurate time stamping
becomes especially important if there is a need to correlate a
transient voltage with another measurement, such as those obtained
with a lightning location system.
[0015] The micro-controller can provide output magnitude and time
data in real time or from the memory data. The output can be
monitored via an Ethernet connection 152, an RS232 connection 154,
or other communication mode, such as a two-way radio or cellular
data link. The non-volatile memory can be, but is not limited to, a
memory device, such as a FLASH memory, a hard disk drive, or a
CD-rom. The transient recorder includes a gain select circuit 144
coupled to the micro-controller. The gain select circuit is also
coupled to the input amplifiers to selectively adjust the gain of
the amplifiers.
[0016] In operation, the transient voltage recorder may be used to
monitor power and communication lines susceptible to induced and/or
direct effects from lightning, however the transient voltage
recorder is not limited to measuring the transient voltage effects
of lightning nor is it limited to power or communication lines. A
typical lightning strike consists of a first voltage transient
followed by one or more subsequent voltage transients of similar
intensity. The present recorder detects the first transient and
adjusts itself to capture the subsequent transient voltages.
[0017] During operation, the threshold detector is triggered when
any of the incoming voltage signals exceeds a threshold voltage.
The transient recorder acquires data from all of the input
channels, preferably simultaneously. A trigger signal from any
channel will cause all of the channels to digitize. The transient
recorder continuously digitizes incoming waveforms at a rate of
mega samples per second (MS/s), with a sampling rate going as high
as desired, for example 200 MS/s. The incoming digitized signals
are then captured by buffer 132. The threshold value and polarity
for each channel can be independently set. The threshold levels can
be set from 1% to 99% of full scale, in one embodiment. Example
input voltage ranges can be +/-10V, 50V and 100V. Further, the
input termination can be selected, for example among 10, 50, 120
ohms. The threshold detector can be reset within a few hundred
milliseconds. The recorder can be rearmed within a few
microseconds.
[0018] In one embodiment, FIFO buffer 132 includes two sets of
buffers (illustrated in FIG. 2 as a common block). The first set of
buffers is deep enough to store a complete waveform. In one
embodiment, the buffer stores 4 k bytes for a 200 .mu.s record,
sampled at 20 MS/s. The buffer is maintained at a level of about
one-half of its capacity during normal monitoring. When the
threshold circuit is triggered, the first set of buffers is allowed
to fill-up to capacity. When the first buffers are full, data is
transferred to the second set of buffers. As such, the recorder
captures information prior to the trigger operation. The depth of
the first and second set of buffers can be selected to maintain
enough storage as needed.
[0019] The transient voltage recorder detects when a transient
voltage is large enough to saturate the input amplifiers (which
results in signal clipping) or is too small to be recorded. That
is, the threshold detector monitors the output of the amplifiers
and determines if a transient voltage is present (exceeds a pre-set
threshold voltage). As explained, the threshold detector monitor
signals the micro-controller when a transient voltage is present.
The digital output of the analog-to-digital converter 130 is
processed by the micro-controller to determine if signal clipping
is present or if a signal is too small for detections. A clipped
signal will provide several voltage samples having the same digital
value. A too small signal can be detected when signals from other
channels at the same threshold are recorded and the too small
signal is not recorded.
[0020] In response to detecting signal clipping, the
micro-controller instructs the gain controller to adjust the
sensitivity (gain) of the amplifier(s). That is, the gain of the
amplifier(s) is reduced. In response to a too low signal, the
micro-controller instructs the gain controller to increase the gain
of the amplifier(s). After the amplifiers have been adjusted, the
subsequent lightning induced voltage transients are detected and
stored in memory. The subsequent voltage transients are correctly
acquired (without amplifier saturation). Following the end of the
lightning event (about one second of inactivity), the micro
controller restores the amplifier gain to a default value.
[0021] Using the FIFO buffer, the transient voltage recorder allows
for recording of activity preceding the onset of the transient
(such as 100 microseconds) and activity following the onset (also
100 microseconds by default). An operator can remotely select a
data-sampling rate, for example, from a 20 mega-samples per second
default rate, and increase a recording time. The relative duration
of the preceding time and the post-trigger time can also be
remotely selected while maintaining just a few microseconds of dead
time between subsequent recordings.
[0022] In one embodiment, the recorder can independently adjust the
gain of each amplifier based upon its output. In addition, the
recorder can store voltage data from each channel when triggered by
any of the channels. That is, a trigger from any of the monitored
channels automatically initiates data acquisition from all
monitored channels.
[0023] A voltage transient recorder has been described that can
detect rapidly induced transient voltages. The recorder detects a
transient voltage and adjusts input amplifiers to accurately record
transient voltage magnitudes. The recorder stores voltage data from
numerous monitored channels, or devices. The data is time stamped
and can be output in real time, or stored for later retrieval. The
transient recorder, in one embodiment, includes an
analog-to-digital converter and a voltage threshold detector. When
an input voltage exceeds a pre-determined voltage threshold, the
recorder stores the incoming voltage magnitude and time of arrival.
The recorder also determines if its input amplifier circuits clip
the incoming signal or if the signal is too low. If the input data
is clipped or if the signal is too low, the recorder adjusts the
gain of the amplifier circuits to accurately acquire subsequent
components of the voltage transients.
[0024] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement, which is calculated to achieve the
same purpose, may be substituted for the specific embodiment shown.
This application is intended to cover any adaptations or variations
of the present invention. Therefore, it is manifestly intended that
this invention be limited only by the claims and the equivalents
thereof
* * * * *