Selection
NTP vs 1PPS vs IRIG-B accuracy by channel
1PPS, IRIG-B, Modbus, and NTP are different channels—mixing them in RFQs causes acceptance disputes.
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.
RS-485 Modbus exposes absolute time registers (including milliseconds) for PLC/SCADA polling at millisecond resolution.
Ethernet NTP depends on switch jitter, client stack, and load. LAN results are often millisecond-class. Never rewrite “10 ns RMS” as “10 ns on the NIC”.
Write RFQ and acceptance criteria per channel, and cite the shipping datasheet include/exclude list.