Analog and Digital I/O

Model 426

Model 426

Six quadrature encoder channels
 with 24-bit resolution

Four 14-bit D/A outputs

Sixteen 14-bit differential A/D inputs, 50 kHz rate, FIFO buffer

Watchdog timer

Forty-eight bi-directional digital signals for solid state relay boards

32 programmable interrupts for counters and digital I/O

Half-size PC/ISA compatible


The Sensoray Model 426 low cost interface saves space in ISA bus systems by combining five functions into a half-size module. Five flat cables connect the Model 426 to external breakout boards.

Six 24-bit up/down counter channels are optimized for incremental encoders. Each channel accepts two phased TTL or RS-422 signals plus an index signal to track encoder direction and displacement. Each input is conditioned and synchronized to the 426’s internal clock. Unlike conventional counters, the 426’s counters do not accumulate errors when the encoder dithers or changes direction. The 426 supplies 5 volt power to each encoder channel. All counters are programmable and may optionally generate interrupts.

Sixteen differential input channels are multiplexed to a sample/hold and successive approximation A/D. A software-programmable amplifier allows gains of 1,2,4,8 for Model 426A and gains of 1,10, 100, 1000 for model 426B. A 512 sample FIFO is available for storing A/D readings.


Four voltage outputs may be programmed for +/- 10 volts. A unique circuit prevents unpredictable D/A outputs during CPU initialization. All outputs are reset to zero volts whenever a bus reset occurs.

The 426’s watchdog timer may be connected to the bus reset via a 2-pin connector. It may be enabled or disabled under program control. The timer is automatically disabled whenever a bus reset occurs.

Digital I/O
The model 426’s forty-eight digital lines have standard pin outs for solid-state relay boards. Each line is software programmable as an input or output. Thirty-two inputs may be programmed for edge detection and interrupts. The status of output lines may be monitored by software. Whenever a system reset occurs all output channels are turned off.

Operating temperature -25C to 70C
PC bus interface I/O mapped, 64 ports
Input power < 3 watts
A/D Converter
Number of channels 16 differential
Input resistance 100 MW
CMRR 100 dB minimum
Max common mode
5 volts
Resolution 14-bits
Input ranges Model 426A +/- 10, 1.0, 0.1, 0.01 V
Model 426B +/- 10, 5.0, 2.5, 1.25 V
Offset error +/- 1/2 LSB
D/A converter
Conversion time 20 mS
Resolution 14-bits
Offset error +/- 2 bits
Output voltage +/- 10 volts
Output resistance 87 W
Digital I/O
Number of channels 48 bidirectional
Output voltage 0 to 5 V open collector
Output sink current 100 mA @1.1 V
Encoder I/O
Number of channels 6 quadrature, 24-bit
Input voltage TTL or RS-422
Input frequency 350 kHz
Watchdog Timer
Time-out 500 mS

2-pin connector may be connected to th bus reset line to allow a system reset from software

Acessory Ordering Information
Amalog I/O 7409C
18” analog cable, 40-pin 7409C1
1 meter analog cable, 40-pin
Small screw terminal board 7409TB
Terminal board w/proto area 7409TC
Terminal board for DIN rails 7409TDIN
Digital I/O
18” digital cable, 50-pin 7501C
1 meter digital cable, 50-pin 7501C1
24 position relay board 720RB
24 position relay board with DIN mounting hardware 720RBDIN
18” encoder cable, 20-pin 7502C3
1 meter encoder cable, 20-pin 7502C4
Encoder terminal board 7502TA
Encoder terminal board with DIN snap rails 7502TDIN