Product Core Brief

• Model: YS1700-020/A31
• Brand: YOKOGAWA
• Series: YS1000
• Core Function: Programmable single-loop PID controller with RS-485 communication for process regulation.
• Product Type: Programmable Indicator Controller
• Key Specs: RS-485 (Modbus/YS Protocol) | 100V AC / 24V DC | YS100 Panel Compatible
• Condition: New Surplus / Original

Product Introduction

YOKOGAWA YS1700-020/A31 is a programmable indicator controller from the YS1000 series. This YOKOGAWA YS1700-020/A31 unit delivers single-loop PID control with function block programming, dual-CPU fail-safe architecture, and RS-485 communication supporting Modbus, YS protocol, and point-to-point links.

The “-020” suffix confirms YS100 panel cutout compatibility, while “/A31” designates the RS-485 comm option. The YOKOGAWA YS1700-020/A31 supports up to 400 function blocks or 1000 lines of text, with control cycle times as fast as 0.05 seconds.

Key Technical Specifications

Quality Control Process

Every YOKOGAWA YS1700-020/A31 leaving our bench goes through a full functional workout. We start with a power supply tolerance sweep — ramping from 85V to 130V AC and 18V to 30V DC to confirm stable operation across the full range. Analog input accuracy is verified at 0%, 50%, and 100% span using a calibrated process calibrator. Control output tracking is checked against setpoint changes to confirm PID response within the 0.05s cycle time. RS-485 communication is stress-tested with Modbus polling at maximum baud rate for 2 hours minimum. Finally, the dual-CPU failover is triggered deliberately — we pull the display CPU and confirm hard manual output still holds. Units that flinch get scrapped.

Replacement Pitfall Guide

❗ Terminal Spacing Differs from YS100: The “-020” type matches the YS100 panel cutout, but terminal-to-terminal pitch is different. Don’t assume your existing wiring harness drops straight in. Re-terminate field wires to the new terminal positions — or you’ll cross 24V DC onto a signal input and fry the front end.

❗ RS-485 Bias and Termination: The /A31 option uses RS-485. On long bus runs, missing termination resistors cause reflection errors that look random. Always terminate the first and last node. Add bias resistors if the bus idles high-impedance.

❗ AC/DC Power Selection: This unit accepts 100V AC and 24V DC simultaneously on different terminals. Wiring 220V AC to the 100V AC input will destroy the power stage instantly. Verify your plant supply voltage before energizing — though your mileage may vary depending on regional transformer taps.

❗ Non-Volatile Memory Means No Battery Swap: This controller uses flash memory, not a backup battery. If you’re replacing an older YS100 that had a battery, don’t go hunting for a battery compartment. But do verify your program is saved to non-volatile memory before powering down for installation.

Keep these in mind and you’ll cut 90% of rework time.

Compatibility Matrix & Benchmarks

• I/O Accuracy (Voltage Input): ±0.1% of span
• I/O Accuracy (Current Output): ±0.2% of span
• Fail-Safe Response: Hard manual override activates within 1 scan cycle on dual-CPU fault

Need help with the program migration from YS100 to YS1700? I can walk you through the YSS1000 software steps.