Selection
NTP vs 1PPS vs PULSE vs IRIG-B accuracy by channel
1PPS, PULSE, IRIG-B, Modbus, and NTP are different channels—mixing them in RFQs causes acceptance disputes.
Updated 2026-08-22
Decision
Write 1PPS / PULSE / IRIG / Modbus / NTP per channel—never mix figures.
Notes
Internal / GNSS 1PPS figures describe the module and discipline loop—useful for factory checks and hardware edge reference.
TTL 1PPS out is for scopes, DAQ cards, and nodes that need a hardware second edge—not a calendar message. On SY-1231 the jack is a 3.3 V GNSS second edge.
PULSE (四针端子 Pin4) is a UTC-minute PPM (default 200 ms, LOCK only)—not 1PPS and not IRIG.
RS-485 Modbus exposes absolute time registers (including milliseconds) for PLC/SCADA polling at millisecond resolution.
IRIG-B time code is on SY-4096 hardware time I/O; this SY-1231 respin has no IRIG.
Ethernet NTP depends on switch jitter, client stack, and load. LAN results are often millisecond-class. Never rewrite internal second-edge figures as “nanoseconds on the NIC”.
Write RFQ and acceptance criteria per channel, and cite the shipping datasheet include/exclude list.
FAQ
- What is the decision?
- Write 1PPS / PULSE / IRIG / Modbus / NTP per channel—never mix figures.
- What are the key points?
- 1PPS, PULSE, IRIG-B, Modbus, and NTP are different channels—mixing them in RFQs causes acceptance disputes.