Important product details|
Detailed information about: FFT
The USB bus fragments packets and sends it with a clock rate of 1000 Hz, i.e. one packet per millisecond. USB 2 even divides the packets further into micro frames. Any data sent from or to the USB device have to be transmitted in packets of this type. So the reaction time of the computer has a lot of latency caused by the USB bus because it only can send a command once a millisecond. Bidirectional communication means to send a command, receive the answer, calculate the control value and send it and only afterwards a control system can set its new values. To slow for time critical applications! The signal processor integrated in any of the MultiChoice USB cards make the functionality available where it is needed: on the measurement card. Any control processes can be performed on the measurement card itself so the PC and the slow packet driven communication are decoupled of the control task. The only remaining task of the PC is to transmit net set values to the measurement card.
Because of the latencies of the USB bus measured values have to be buffered on the cards to achieve continuous data transfer and to ensure data integrity if the measurement data. The best solution would be a memory of indefinite size. Because this is not possible with real world technology the measurement cards of the MultiChoice USB series use the available memory of 1.5MByte as flexible as possible and divide the capacity in a manner where any measurement function can work with a maximum of available memory.
»Signal Processor allows for maximum Flexibility
MultiChoice USB cards are equipped with a signal processor which not only supports the measurement itself but it also processes many other tasks. An overwhelming variety of functions allow the generation of real time signals, run time filters, PID control, and FFT and many more. Because of multi sampling and arithmetic averaging (oversampling) the precision of the measurement is increased further.
»Multi Function Counters
Any of the MultiChoice PCI and USB measurement cards offer modern counters designed with a FPGA. These counters allow not only the functionality known from standard counters but also offer modes like pulse counting, measuring with fixed frequencies and any counter channel offers even many possible selections of pulse counting (up/down), frequency measurement with 4 selectable resolutions, period length measurement, and pulse width measurement. Additionally incremental counters and SSI interface are usable to further enlarge the spectrum of available counters. Outputting frequency modulated pulse width signals is one more impressing functionality.
Signal inputs of MultiChoice USB are configurable. In additions to selectable gains of 1x, 2x, 4x, and 8x any channel can be switched between bipolar and unipolar measurement range to make available the optimal resolution. The digital inputs/outputs can be set to input and output individually so the number of inputs and outputs can be adapted to the needs of the application.
Any specification data of the measurement cards as far as maximum read respectively output rates are concerned are given as effective value at the specified precision. Other vendors sometimes publish performance data which are not really true because high sample rates lead to significant decreases in precision.
»Disruption free Pulse Width Output
Pulse width output of MultiChoice cards is free of disruptions. In opposite to many other PWM cards on the market MultiChoice cards end the running period before setting a new value. So there are no phase shifts which are of major importance to proportional valves and the like.
»Extensive protection of the Measurement Card
Analog inputs of MultiChoice USB cards are protected against over voltages up to + 40V in operation/non operating so even higher voltage spikes do normally not damage the multiplexer.
»High Number of Channels
MultiChoice measurement cards are available with up to 32 analog inputs, 2 counters, 4 analog outputs, and 24 digital inputs/outputs. Optionally pulse width modulation, incremental counters and SSI interface can be installed. If more channels are needed up to four measurement cards can be operated in parallel.