Industrial Engineer · phase 12 of 16 · noun

Speed Reference

Commanded speed or frequency value received from the keypad, analog input, preset, PID, or network.

The Explain card

Plain English
The speed reference is the value that tells the drive how fast to run. It can come from a potentiometer, an analog input, a preset, a network word, the keypad, or the drive's own PID loop.
Example
A PLC writes 45 hertz into the drive's reference word over EtherNet/IP. The drive ramps to 45 and holds there until the word changes.
Why it matters
The reference source is a parameter, and a drive listening to its keypad while the PLC writes to the network runs at whatever the keypad last said. When a motor runs at the wrong speed, ask where the reference is coming from before you ask why.
Hook
How fast, from a source the drive was told to trust.

Word knowledge

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

During commissioning, the technician raises the Speed Reference to 45 Hz and confirms that the conveyor motor accelerates without an overcurrent trip.

Why these words
  • speed Old English spēd, success or prosperity names the quantity being controlled
  • reference Latin referre, to carry back or relate marks the quantity as the controlling point used by the drive
Where it came from
Origin
English technical compound formed from Old English spēd and reference, ultimately from Latin referre
Entered the language
20th century
What changed
Speed shifted from success and prosperity to rate of motion, while reference developed from an act of referring to a point used for comparison or control.
How it is spelled
Pattern
Speed keeps the common ee spelling for the long e sound.
Pattern
Reference ends in the noun-forming spelling -ence.
Breaks the pattern
Reference has one r before -ence, although referred and referring double the final r.

Spelled like

  • speedy
  • speedometer
  • preference
  • inference
Broken into chunks
  • speed
    • speedy
    • speedometer
  • refer
    • referral
    • referent
  • ence
    • preference
    • inference
What it sits beside

Same subject

  • frequency command
  • speed feedback
  • acceleration ramp
  • motor nameplate frequency

Same shape

  • torque reference
  • frequency reference
  • current reference

Drive control quantities

  • speed reference
  • torque reference
  • current reference

Drive commissioning terms

Where it sits in the deck

Phase 12: VFD Commands, References, and Stopping

Starting, referencing and stopping, including the several very different things a drive can mean by the word stop.

Neighbours in this phase