Engineering notes
Notes on the parts of a rack PDU that decide what a hall can measure: metering accuracy, protocol, outlet combination and three-phase balance. Each one is written against a configured unit and the values it reports.
- Metering
- ±1% + 1 digit
- Energy total
- 1 grade · 0.1 kWh
- Ethernet
- 10/100M × 1
- Serial
- RS485 × 1
- Protocols
- SNMP · Modbus
Notes index
Notes written from the meter side of a rack feed
Each row names the decision it covers and the published figures it uses. The unit behind them reports total current at a 0.1A scale, energy at 0.1 kWh on a 1 grade total, and answers on 10/100M Ethernet or RS485.
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Note 01
What ±1% metering accuracy means in a rack PDU
A tolerance on the meter inside the unit and a billing-grade energy total are two different claims. This note separates them line by line, at the scales the unit reports.
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Note 02
SNMP vs Modbus for rack PDU monitoring
Ethernet and RS485 sit on the same monitoring board and carry the same meter values. The choice follows what already polls the row, not which protocol is newer.
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Note 03
C13 vs C19: choosing outlet combinations
Outlet rating and feed size are separate limits. This note walks a mixed combination against a 110V~250V AC input and the 50Hz~60Hz supply at the rack.
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Note 04
Three-phase PDU load balancing basics
Balance is a per-phase current comparison read at one scale. This note covers the 0.1A step, the ±1% + 1 digit tolerance and a worked model example at AC 415V.
Register view
Values every note on this page is checked against
The same meter data reaches the rack display, a poller and the event log. These are the scales and ports it arrives on.
Metering accuracy
±1%
Current, voltage and active power on every reporting line, at ±1% plus one digit.
Energy total
1 grade
Billing-grade total on a 0.1 kWh step, kept per reporting line.
Current scale
0.1 A
Total per feed, and per outlet on switched builds, on the same poll.
Ethernet
10/100M
One port on the monitoring board, for a poller or the embedded web server.
Serial
RS485
One port on the same board, for a Modbus master in the row.
Event store
20,000
Dated threshold entries, with the clock held through a power cut.
Ambient sensor
-30°C
Range to 100°C at 1°C resolution, beside humidity from 1% to 99%.
Remote switching
per outlet
Or per group on switched builds, addressed over the same interface.
Request a quote
Send the rack lines and the reading you need
Outlet combination, current per feed, metering depth and remote switching. The reply names the note that matches the build and carries a per-line specification sheet, in English.
Reply within 12 hours on working days. No lead time and no minimum quantity figure is published on this site.
