Overview of NI Data Acquisition Equipment Technology

NI M series devices integrate three main technologies for timing, performance, and accuracy: NI-STC 2, NI-PGIA 2, and NI-MCal. NI USB M series devices provide high-performance signal flow characteristics on the USB bus. All industrial M series equipment and some selected USB M series equipment are equipped with equipment protection and isolation to remove ground loops.

NI-STC 2

NI-STC 2 is a custom-designed application specific integrated circuit (ASIC) that can control the system's timing, synchronization, and all input and output data acquisition operations. NI-STC 2 provides:

• 6 DMA channels-dedicated DMA controllers are provided for each function

• Digital I/O line with clock (up to 10 MHz)

• 32-bit counter/timer with encoding compatibility

• Provide RTSI bus signal generation and wiring for synchronization between multiple devices

• Provide generation and wiring of internal and external timing signals

• PLL for clock synchronization

NI-PGIA 2

In order to ensure measurement accuracy, NI has designed customized NI-PGIA 2 technology for M series devices. The NI-PGIA 2 on every M Series device is optimized for cost, speed, and accuracy. For example, the NI-PGIA 2 of the high-precision M series family is optimized for 18-bit fast stability, low noise, and high linearity. NI-PGIA 2 technology improves the accuracy of the device by reducing the settling time and maintaining the specified resolution at the maximum sampling rate of the device.

NI-MCal

The M-series devices also include NI-MCal technology, which is a patent-pending linearity and calibration engine that can calibrate thousands of levels and all input ranges. NI-MCal uses a combination of pulse width modulation (PWM) and high-precision voltage reference. The duty cycle of PWM is used to change the level, so self-calibration can be performed at multiple points. Calibration constants are generated and stored on the on-board EEPROM in order to model the nonlinearity of the ADC and correct future measurements. Compared with the traditional two-point calibration, the application of NI-MCal technology improves the measurement accuracy by five times. In addition, the improved accuracy reference on most M series equipment has extended the recommended calibration interval from one year to two years, reducing equipment maintenance costs.

Signal flow

In order to perform high-performance data acquisition on USB M series devices, National Instruments has designed NI data stream technology. NI Data Flow integrates innovative hardware and software design elements to achieve continuous high-speed and bidirectional data flow transmission on the USB bus. This new technology helps engineers realize high-performance applications on the USB bus, which in the past was only possible on internal buses such as PCI.

isolation

Electrical isolation isolates analog input signals that may be affected by dangerous voltages from the low-voltage backplane of the measurement system. NI provides isolation on industrial M series devices and selected bus-powered USB M devices. Isolation can bring the following benefits:

• Protect expensive instruments, users and data from the hazards of transient high voltages

• Improve noise suppression

• Remove ground loop

• Improve common mode voltage rejection