This invention relates to an apparatus for converting a plurality of analog signals into digital signals for transmission to a computer over a computer databus. More particularly, the invention relates to an analog-to-digital conversion device which may be programmably controlled by a digital computer processor, for sequentially transferring a plurality of analog signals into a single conversion device, for developing a sequence of binary signal representations of the analog signals for transmission over a computer databus to a computer processor
Analog-to-digital conversion devices are well known in the art, having been developed as a means for providing signal transformation between devices which generate time-varying analog voltages and devices which operate by virtue of discrete binary signal voltages For example, nearly all forms of rotating shaft devices require time-varying voltages for controlling shaft rotation and position, and such devices are typically electrically or mechanically linked to other shaft-rotating devices for providing analog voltage signal indications which are representative of shaft rotation or position. In order for a computer processor, which operates wholly in the realm of discrete binary voltage signals, to communicate with such analog devices, it has been necessary to develop a wide range of conversion devices at an interface. Utilizing well-known design techniques, computer processors can develop binary drive voltage signals which may then be converted into analog drive voltage signals, for purposes of positioning shaft-rotating machines. Similarly, conversion devices have been developed for receiving analog voltages representative of position or rotation of such shaft-rotating machines, and converting the signals into discrete binary signals for transmission to computer processors.
Any three-axis machine whose position is to be monitored by a computer processor must have three conversion devices, one conversion device for each of the three axes of motion. These axes may be labeled X-, Y-, and Z-axes, or roll, pitch and yaw, or some other convenient frame of reference for the respective degrees of freedom of motion. When the position of three-axis devices are to be monitored, it is convenient to try to capture the voltages representative of all three axes of motion at the same instant of time, so that at a single instant in time the precise position of each axis can be determined. This is preferable to capturing the voltages representative of axis positions in a sequential fashion, because relative motion occurs as between the respective axes even while the information is being processed. Therefore, some degree of error may be introduced by virtue of the time consumed by the measurement mechanism.
In addition to three-axis devices which require essentially three separate analog measurement voltages, there are any number of other analog devices on a typical reasonably complex machine which may require monitoring. Such other devices do not necessarily have an interdependent time relationship, and may therefore be monitored at regular intervals, but in some sort of sequential varying fashion. For example, certain acceleration, velocity, and position devices, as well as devices for measurement of physical parameters such as temperature, pressure, and volume, may need periodic monitoring, but such monitoring is not a critically interdependent requirement. Analog-to-digital conversion devices which interface with these other devices may be monitored at various times and rates, in any sort of random sequence dictated by design and accuracy requirements.
An analog-to-digital conversion device requires, at a minimum, some means of capturing and holding the analog voltage representative of the device position at a moment in time, and a conversion device which can develop a binary signal pattern which is equatable to the captured analog voltage, and a mechanism for transferring the binary signal representation to a computer for further processing. Since the conversion process takes a finite period of time, the analog signal voltage must be fixed during the time required for the transformation process. In the case of multiple-axis device measurements, it is preferable that all of the voltages representative of respective axis positions be captured at the same instant of time, and that all voltages be held until the digital conversion process is completed for all. In the prior art, the typical approach toward achieving this result would be to provide three separate and parallel branches of conversion, wherein each axis analog voltage is separately transformed into a binary representation, more or less simultaneously, and the binary results are then transferred to a computer processor in either parallel or sequential format. This solution requires a full electronics conversion package for each axis, since the conversion process takes place simultaneously for all axes. In addition, if other analog signal voltages are to be converted, it is frequently necessary to provide further analog-to-digital conversion packages for such other signals.
There is a need for an analog-to-digital conversion device which permits simultaneous capture of certain analog signals, but does not require multiple electronic conversion packages corresponding to the number of analog signals being monitored. It is therefore a principal object of the present invention to provide an analog-to-digital conversion system which will economically and accurately transform a plurality of analog signals to binary signal representations
It is another object of the present invention to provide an analog-to-digital conversion device for simultaneously capturing multiple-axis analog signals, for subsequent transfer and processing by a digital computer processor.
It is a further object of the present invention to provide an analog-to-digital conversion system which will sequentially process a plurality of analog voltage signals for transfer through a single computer databus.