* Fast, 12-bit ADC
Applications
You can use the SB-MIO-16E-4 in many applications for automating machines, process monitoring and control, instrumentation, and electronic test functions.
Hardware
Figure 1 is a block diagram of the
SB-MIO-16E-4 circuitry. The major functions are described in the following paragraphs.
Analog Input - The SB-MIO-16E-4 uses CMOS analog input multiplexers connected to multiple analog input channels. The input multiplexers have input overvoltage protection of ±25 V powered on and ±15 V powered off. With the SB-MIO-16E-4, the number of analog input channels available are 16 single-ended inputs, 16 pseudodifferential inputs with a shared common, or eight fully differential inputs (software selectable).Voltage input ranges are software selectable for 0-10, ±5, or ±10 V.
The SB-MIO-16E-4 includes a software-programmable gain amplifier that you can configure voltage gains of 1, 2, 5, 10, 20, 50, and 100 to accommodate both low-level and high-level analog input signals. The board also has a programmable gain of 0.5, which you can use with the input range of ±5 V to acquire signals with a ±10 V input range.
You can attain even better resolution in the same amount of time than it takes for the NI-PGIA to settle to 12-bit accuracy by enabling the Gaussian Dither Generator and averaging the acquired samples. The data returned by the A/D converter will still be 12-bits, however, by virtue of the dither circuitry and averaging, your data will be as accurate as an A/D converter with more bits. The 12-bit output of the ADC is software configured for two's complement numbers in bipolar mode, or straight binary numbers in unipolar mode.
The SB-MIO-16E-4 performs both single A/D conversions or infinite multiple A/D conversions of a fixed or infinite number of samples.
The SB-MIO-16E-4 has a guaranteed sampling rate of 250 kS/s. The sample timer for A/D conversions has a resolution of 50 ns or 10 µs. You can also program the sample timer for conversion rates as low as .00596 S/s, or 1 sample every 168 seconds.
The SB-MIO-16E-4 uses the National Instruments NI-PGIA programmable instrumentation amplifier, which guarantees full 12-bit accuracy when scanning multiple channels at the same gains at all scanning rates. Regardless of the gain used, the NI-PGIA settles to within the 12-bit accuracy of the ADC within 2 µs. Thus, the boards can scan several channels at 250 kS/s, preserving the full accuracy of the board at all gains.
A 512-word configuration memory makes it possible for the SB-MIO-16E-4 to sample channels in any order with a different gain for each channel. Furthermore, you can individually program each channel in the configuration memory as bipolar or unipolar and differential or single ended. In multichannel scanning mode, the maximum conversion rate per channel is 250 kS/s divided by the number of channels scanned.
The SB-MIO-16E-4 performs data acquisition in the interval scanning mode. This fully accommodates single and multichannel acquisition in both round robin and pseudo-simultaneous fashions. With the addition of external conditioners, such as SC-2040, you can perform true simultaneous acquisition. The time between scans in a pseudo-simultaneous sequence is determined by the scan interval, while the time between samples is determined by the sample interval.
Digital Triggering - With the internal and external pretrigger and posttrigger modes, the boards can acquire data either after, or both before and after, an internal or external trigger condition occurs. In pretrigger mode, the sample sequence is initiated through software or by a pulse at any software selectable programmable function input (PFI) line. A second trigger causes the selected number of data points before and after the trigger to be returned. In posttrigger mode, a single software trigger or pulse at TRIG1 causes a programmed number of samples to be acquired. You can enable external triggers through software.
Analog Output - The SB-MIO-16E-4 has two double-buffered, multiplying, 12-bit DACs connected to two analog output channels. You can configure each channel for unipolar (0 to Vref) or bipolar (-Vref to Vref) operation through software. The reference voltage (Vref) is also selected through software and can be the 10 V internal voltage reference or an external reference. With the internal reference, output voltages are ±10 V in bipolar mode and 0 to 10 V in unipolar mode.
You can handle timed updating, which is useful in waveform generation applications, by using DMA from onboard memory. An onboard 24-bit timer can clock the DACs for waveform generation, and generate interrupt and DMA requests for servicing the DACs. An onboard, DSP DMA controller handles updating rates to 250 kS/s.
System Timing Controller - The SB-MIO-16E-4 uses the National Instruments DAQ-STC system timing controller for time-related functions. The DAQ-STC consists of three timing groups that control analog input, analog output, and general-purpose counter/timer functions. The General-Purpose counter/timer group contains two 24-bit up/down counter/timers that are always available for general time-related functions, such as pulse-train generation, pulse output, buffered counter operations, and event and frequency counting, even while the board is performing complex analog I/O operations. You can configure each group independently with timing resolutions down to 50 ns or 10 µs.
The timing I/O capabilities of the DAQ-STC are called programmable function inputs (PFIs). The PFIs, which are 10 generic signal pins on the I/O connector, can be programmatically connected to timing capabilities such as triggering, conversion, clocks, and so on.
Self-Calibration - The analog inputs and outputs of the SB-MIO-16E-4 have calibration circuitry to correct gain and offset errors. Using software to accommodate changing environmental conditions, you can calibrate the board to avoid analog I/O errors caused by time and temperature drift at run time. No external circuitry is necessary; an internal reference ensures high accuracy and stability over time and temperature. Factory calibration constants are permanently stored in an onboard EEPROM and cannot be modified. A modifiable section of the EEPROM stores user-modifiable constants. You can return the boards to their initial factory calibration by accessing the unmodified factory constants.
Digital I/O - The SB-MIO-16E-4 includes eight digital I/O lines. The direction of each of the digital I/O lines is software programmable on a per line basis. The digital input circuitry has an 8-bit register that can read back the outgoing digital signals and also read incoming signals. The digital input is TTL compatible and the digital output is CMOS compatible.
I/O Connector - The I/O connector for the SB-MIO-16E-4 is a 68-pin male SCSI-II type connector, diagrammed in Figure 2. ACH<15..0> are the 16 analog input channels. AISENSE is the common signal line for pseudodifferential analog input. DAC0OUT and DAC1OUT are the two analog output channels. EXTREF is the input connection for an external reference voltage for the analog output channels. DIO<0..7> are the eight digital I/O lines. SCANCLK (multiplexer scan clock) and EXTSTROBE* (external multiplexer strobe) can drive the AMUX-64T. External pre and posttrigger, gate, and conversion signal inputs for external control of A/D conversion timing are available at the I/O connector. The external waveform trigger and update signal inputs used to start and update the analog output DACs are also available at the I/O connector. GPCTR_GATE, GPCTR_OUT, and GPCTR_SOURCE are the gate input, counter output, and counter input, respectively, for the 24-bit counter/ timers. FREQ_OUT is the programmable frequency output from the DAQ-STC.
Software
The following software is included with
the SB-MIO-16E-4:
* NI-DAQ for Sun
The following application software is available separately:
* LabVIEW
Detailed information on this software can be found in Section 2.
Part Numbers
SB-MIO-16E-4 and software 776794-01
68-pin Connector Blocks and Cables
SCB-68 shielded
connector block 776844-01
TBX-68 DIN rail mountable
connector block 777141-01
CB-68LP low-cost
connector block 777145-01
SH6868 68-pin to 68-pin shielded cable
1 m 182419-01
2 m 182419-02
5 m 182419-05
10 m 182419-10
R6868 68-pin to 68-pin ribbon cable
1 m 182482-01
50-pin Connector Blocks and Cables
CB-50 DIN rail mountable
connector block 776164-90
CB-50LP low-cost
connector block 777101-01
SH6850 68-pin to 50-pin shielded cable
1 m 776784-01
2 m 776784-02
5 m 776784-05
10 m 776784-10
R6850 68-pin to 50-pin ribbon cable
1 m 776842-01
