Hola Es posible adquirir señales en tiempo real del orden de los 100 kHz por el puerto paralelo?. De no se posible, me podrian explicar por qué y si hay alguna forma de lograrlo?. saludos Ing. Eliecer Rodriguez

si fuera posible ya habria osciloscopios de calidad con la pc.

Aca una innovadora manera de tratar la adquisicion por PP...de la pagina www.dataq.com Change The Way You Think We are creatures of base 10 and the alphabet. It gives us comfort to know that the files our data acquisition programs create can be displayed, printed and interpreted as easily as reading the morning paper. Unfortunately, base 10 is not the number system of your PC and it doesn't know the difference between A and Z. To achieve high speed real time data acquisition, you have to accept the PC for what it is and work with it on its terms. That means a base 2 number system and binary-coded files. To learn why, lets look at a single sample acquired from a 12-bit data acquisition device. Computers like to work in groups of bits that are a multiple of 8 (one byte). The 12-bit binary number representing the sample's value fits nicely into a 16-bit word (only 2 bytes) and it's efficient for the PC to write it to disk in this form. But you'd prefer the PC to convert the sample to its ASCII equivalent (one we can read) before writing the value to disk. This simple, seemingly logical request explodes the number of bytes written to disk by at least a factor of 2.5. The range of our 12-bit ADC is 0 to 4095 counts. Writing counts to disk in ASCII-readable form consumes one byte for each character, plus a delimiter (like a comma) for a total of 5 bytes. In the more likely case that you want data stored in meaningful units (like psi), multiplying by m and b scaling constants yields an even larger number of digits that must be written to disk. Your 2-byte binary representation of a single sample could easily explode to 10 or more ASCII characters (bytes). The resulting 5:1 burden will tax your PC and the hard drive and ultimately limit your maximum data acquisition rate. Here's a hard and fast rule: Real time data acquisition programs that store data to disk as ASCII characters are not high speed solutions. Any well conceived program not only stores data to disk in a two's complement or other non-text, binary format, but will also provide the ability to convert any range of waveform data to ASCII after acquisition. Detecting Relay Chatter in Delta Launch Vehicles Imagine the vibrations you'd encounter as you were launched into space by a rocket. Now imagine how these vibrations can affect on-board control circuits. Since the failure of even one such component during launch can be both costly and tragic, engineers strive to simulate as much of the mission as possible on the ground. One area of particular concern was relay chatter caused by the tremendous vibrations of flight. A simulation was carried out to determine whether on-board relay assemblies remained closed when subjected to a 70g, 100 Hz to 3 kHz random vibration. Engineers had defined a minimum sample interval of 5 µs with a total data acquisition time of 3 minutes. This translated to a 200,000 Hz sample rate and a data file size of about 72 megabytes. It also precluded use of an older data acquisition product that had a top sample rate of 50,000 Hz. Instead, a small DC current was injected into the relay circuit and connected to a DATAQ Instruments model DI-400 data acquisition card (now obsolete) running under WinDaq/Pro real time software. This combination is capable of sample rates to 500,000 Hz. Any break in the relay circuit caused by vibration would immediately show as a spike on WinDaq/Pro's real time display (Figure 3), thus allowing relay performance to be judged on-the-fly. Subsequent to the test, data files created by WinDaq/Pro can be further interpreted using WinDaq Waveform Browser software. The disk streaming capabilities of both software packages allows data acquisition and analysis independent of data file size. SALUDOS...Gracias por leer !!!

Gracias a los colegas por los comentarios, pero alguien me podria dar detalles mas tecnicos?

Si se puede pero necesitás la interface adecuada y son muuy caras. Se venden equipos con las entradas y controles de un osciloscopio y la visualización de imágen se hace por medio de pc hasta por medio de una lan. Los oscoscopios digitales tienen salidas para visualizar y procesar las señales. Si lo que querés es armar algo mas barato que un osciloscopio no se puede. Señales analógicas sólo podés entrarlas por una placa de audio y esta limitada al ancho de banda de audio. Por los puertos serie y paralelo sólo podés entrar valores digitales entre 0 y 5v. Saludos

Hola Pato, me parece interesante la cita. Mi idea es atender un conversor de 2MSPS por el puerto paralelo y sacarle todas sus potencialidades, por supuesto desarrollaré un software para esto. Mi pregunta es si las tareas que realiza el sistema operativo normalmente no me influirán en estas frecuencias que usted habla. He visto por ahi que hay quien utiliza una memoria temporal para almacenar los datos adquiridos y despues el software se encarga de leer los datos de la memoria y procesarlos.

Para Miguelete y todo el foro.En el articulo manuales circuitos de osciloscopio , dan una direccion a una pagina , donde se construye , un osciloscopio de 2 canales de 40 msa/s , es un proyecto de fin de carrera de 2 estudiantes de ingenieria electronica , tiene muy buena y completa informacion para lo que esta tratando aqui .La pagina es de Pablohoffman.

normalmente para esas velocidades, en mis tiempos los adquirian directamente del bus isa, ahora pues esta el pci y habira que ver si con usb se puede. Saludos http://sine.ni.com/nips/cds/view/p/lang/en/nid/201936

Hola Torreslamora : esta para USB , pegale una mirada y vas a ver el proyecto completo.Saludos. PD: no se si te andara el economizador de energia , yo por aqui le di algunos circuitos a uno alumnos de unas facultad para que lo investiguen.

[quote]Speed Q: How can Parallel Port ISA card support quoted rates of data transfer in excess of 1MB/sec ? As far a I know every in/out command for an ISA bus address takes at least 1 microsecond to perform REGARDLESS of processor speed ? A: A simple parallel-port read or write does take one ISA-bus cycle, and on most systems, the bus speed is around 1.3 Mhz, so one cycle is a little under 1 microsecond. A complete data transfer on the original parallel port usually takes at least 4 cycles, however: check the Busy status, write the data, bring Strobe low, then high. On ports that support EPP and ECP modes, in these modes the port hardware does the handshake, and a complete transfer can take place in 1 bus cycle. There are at least two ways of getting faster data transfers: Some ports support a "fast mode" that uses the ISA bus's NOWS (no wait state) signal to cause the CPU to skip 3 wait states. This mode is twice as fast, or around 2.7 Mhz. ECPs also include hardware support for data decompressing (& sometimes compressing, though that's often left for software), so the effective rate of data transmission can be much faster than the number of bytes written or read per second. Also, ECPs may be able to transfer data between the host's and peripheral's ECP buffers at rates greater than 1 Mhz, though the buffers are typically just 8 bytes. [/quote]