Low-Cost Multifunction I/O Board for ISA
Lab-PC+ Features[CLICK for graphics] *** I/O Connector [CLICK for graphics]
12-bit ADC - 83.3 kS/s sustained sampling rate - 8 single-ended or 4 differential channels - Programmable gain of 1, 2, 5, 10, 20, 50, or 100 - Input range of 0 to 10 or ▒5 V - 512-sample FIFO ADC buffer - Internal or external A/D timing * Two 12-bit, double-buffered DACs - Unipolar (0 to 10 V) or bipolar (▒5 V) output - Onboard timer for waveform generation * 24 digital I/O lines, configured as three 8-bit ports - Software configurable for input, output, or bidirectional transfers - 2-wire handshaking modes - Interrupt generation * 3 independent 16-bit counter/timers for frequency counting, event counting, and pulse output applications * 8-bit DMA interface * Driver software - NI-DAQ for Windows 95/NT/3.1/3.1J, DOS, and DOS/V * Application software - LabVIEW, LabWindows/CVI, LabWindows, Measure, ComponentWorks, and VirtualBench Software Included * NI-DAQ for Windows 95/NT/3.1/3.1J * DAQWare
The Lab-PC+ is a low-cost, multifunction analog, digital, and timing I/O board for ISA computers. It has a 12-bit ADC with eight analog inputs, configurable as eight single-ended or four differential inputs, two 12-bit DACs with voltage outputs, 24 lines of TTL-compatible digital input and output, and three user-available 16-bit counter/timer channels for timing input and output. The PC bus interface has 8-bit data paths with circuitry for interrupts and DMA.
For additional analog inputs and signal conditioning, you can use the SCXI signal conditioning system to multiplex, isolate, and amplify up to 384 low-level signals into a single board.
The Lab-PC+ is ideal for laboratory work in industrial and academic environments. The multichannel analog input is useful in signal analysis, data logging, temperature measurement, and DC voltage measurement. The analog output channels can generate experimental stimuli, machine and process control signals, and analog functions. You can use the 24 TTL-compatible digital I/O lines for switching external devices such as transistors and solid-state relays, for reading the status of external digital logic, and for generating interrupts. You can use the three counter/timers to synchronize events, generate pulses, and measure frequency and time. The PC equipped with the Lab-PC+ is a versatile, cost-effective platform for laboratory test, measurement, and control.
Figure 1 shows the block diagram of the Lab-PC+ circuitry. The following paragraphs describe the major functions of the hardware.
The Lab-PC+ has two CMOS analog input multiplexers connected to eight analog input channels. The input circuitry gives input overvoltage protection of ▒45 V powered on or powered off. You can use the analog input channels as eight single-ended inputs, eight pseudodifferential inputs with a shared common, or four fully differential inputs.
Voltage input range is jumper configurable for 0 to 10 V (unipolar) or ▒5 V (bipolar). A software-programmable gain amplifier has gain selections of 1, 2, 5, 10, 20, 50, or 100. The Lab-PC+ has a 12-bit ADC with analog signal resolution of 2.44 mV at a gain of 1. You can achieve Þner resolutions down to 24.4 ÁV by using a higher gain. The 12-bit output of the ADC is automatically sign-extended to 16 bits.
The Lab-PC+ performs both single A/D conversions and multiple A/D conversions of a set number of samples. A 512-word-deep FIFO memory buffers the data during multiple A/D conversions. Multiple A/D conversions can be handled by programmed I/O, interrupts, or DMA.
An onboard counter/timer controls the timing of multiple A/D conversions. The counter/timer generates the sample interval clock with a resolution of 1 Ás. As an alternative, an external signal can generate the timing for the sample interval. Data acquisition with the Lab-PC+ is available in three modes: 1) continuous acquisition of a single channel, 2) multichannel acquisition with continuous scanning, or 3) multichannel acquisition with interval scanning. In the third mode, all channels are scanned at one sample interval, with a second interval determining the time before repeating the scan. Both single A/D conversions and multiple A/D conversion sample sequences are initiated from either software or external timing control signals.
There are two hardware triggering modes - pretrigger mode and posttrigger mode. In pretrigger mode, a programmed number of samples are acquired before a trigger is received at the external trigger input. In posttrigger mode, a programmed number of samples are acquired either immediately, or when a trigger is received at the external trigger input. By combining the pretrigger and posttrigger modes, the Lab-PC+ can acquire data before and after a trigger condition.
Any number of channels between 2 and 8, in single-ended, or between 1 and 4 in differential mode, can be scanned in the multichannel acquisition mode. These channels are scanned in a round-robin sequence, taking one reading per interval, with scanning always occurring in the same order, from the number of channels selected to channel 0.
The Lab-PC+ generates both interrupts and DMA requests on the ISA I/O channel. You can generate interrupts whenever an A/D measurement is available from the ADC FIFO, upon error conditions, when the DMA process has reached terminal count, upon receiving digital I/O handshaking signals, or when one of the onboard timer clocks generates a pulse. You can generate DMA requests whenever an A/D measurement is available from the ADC FIFO.
The Lab-PC+ has two double-buffered 12-bit DACs that are connected to two analog output channels. You can configure each channel independently for unipolar (0 to 10 V) or jumper-selectable, bipolar (▒5 V) operation. The resolution of the 12-bit DAC is 2.44 mV in both polarities.
You can handle waveform generation by programming I/O or interrupts. One of the 8253 counter/timers is used with the DACs for waveform generation. The counter/timer generates periodic interrupts and update signals for the double-buffered DACs.
The Lab-PC+ has 24 digital I/O lines, configurable as three 8-bit ports for input, output, bidirectional, or handshaking modes. Two of the ports can drive Darlington transistors directly for higher-current applications. The digital I/O lines are TTL compatible. The digital output port can sink 1.7 mA on each line.
ISA I/O Channel Interface- The ISA I/O channel 8-bit interface circuitry includes address latches, address decoding circuitry, data buffers, and interface timing and control signals. Interrupt lines 3, 4, 5, 6, 7, or 9 can be jumper selected. You can make 8-bit DMA transfers on jumper-selectable DMA channels 1, 2, or 3 for high-speed analog input operations.
Counter/Timer- The Lab-PC+ uses two 82C53 system timing controllers (STCs) for counting and timing. Each STC contains three independent 16-bit counter/timers. One of the STCs, counter A, is dedicated for A/D and D/A timing.The three counters on the other STC, counter B, are available to you for general time-related functions such as clock output, pulse output, and event and frequency measurement. One of these counters can increase the sampling interval when required. The gate and output of the three counter/timers are available at the I/O connector. The clock source of counters 1 and 2 is also available at the I/O connector. The clock source of the third counter/timer is tied internally to a 2 MHz clock so that an external clock signal is not required. Counter 1 is an option you can use to obtain the scan interval in the interval scanning mode.
I/O Connector[CLICK for graphics]
The I/O connector is a 50-pin male ribbon cable connector, dia- grammed in Figure 2. ACH <0..7> are eight analog input channels referenced to AI Ground. DAC0OUT and DAC1OUT are the two analog output channels referenced to AO Ground. A TTL low-level signal on the EXTUPDATE* pin updates the analog output channels. A rising edge on EXTUPDATE* generates an interrupt on the PC I/O channel, making externally controlled voltage output possible. EXTCONV* can control individual A/D conversions externally. You can use EXTTRIG, the external trigger input for pretrigger or posttrigger applications. CLKB<1..2>, GATB<0..2>, and OUTB<0..2> are the clock, gate, and output of the user-available counter. PA<0..7>, PB<0..7>, and PC<0..7> are the three 8-bit digital I/O ports.
The following software is included with the Lab-PC+: * NI-DAQ for Windows 95/NT/3.1/3.1J * DAQWare
Detailed information on NI-DAQ can be found on page 2-98.
The following software is available separately: * LabVIEW * LabWindows/CVI * LabWindows * Measure * VirtualBench * ComponentWorks * NI-DAQ for DOS and DOS/V Detailed information on this software can be found in Section 2.
Lab-PC+ and software 776703-01 50-pin Connector Blocks and Cables CB-50LP low-cost connector block 777101-01 Type NB1 50-pin to 50-pin ribbon cable 0.5 m 180524-05 1 m 180524-10 2 m 180524-20
For more accessory options, refer to the Related Products list.
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