WattNode Pulse – Option PW – Pulse Width

See MS-17-WNB-Pulse-Option-PW.pdf (Manual Supplement MS-17) for a detailed explanation.

Overview

The WattNode® Pulse meter with Option PW specifies the pulse ON (closed or conducting) period in milliseconds. For example, the following configures 100 millisecond pulse ON periods:

Opt PW=100 

This option is compatible with all other pulse options including P3, DPO, PV, Hz, etc.

Selection

The pulse width can be set as fast as 1 millisecond and as slow as 65 seconds (65000 milliseconds), but in practice, the maximum pulse width PWmax is limited to:

PW_{max}=frac{500}{H!z}

Where Hz is the nominal full-scale pulse frequency, 4.00 Hz is the default unless Option Hz or Option Kh have been specified. The following table lists the maximum pulse width for some common full-scale frequencies.

Full-Scale Frequency Hz Allowable Pulse Width Milliseconds PWmax
100 Hz 1 – 5 milliseconds
20 Hz 1 – 25 milliseconds
10 Hz 1 – 50 milliseconds
4 Hz 1 – 125 milliseconds
1 Hz 1 – 500 milliseconds
0.1 Hz 1 – 5000 milliseconds (5 seconds)
0.01 Hz 1 – 50000 milliseconds (50 seconds)

If your WattNode meter also has Option Kh, then see WattNode Pulse – Option Kh – Watt-Hours Per Pulse for information on computing the full-scale frequency as a function of the Kh and CT amps values.

Limitations

There are a few limitations with Option PW:

  • Only the period when the optoisolator or solid-state relay is ON (closed or conducting) can be specified by the pulse width.
  • The shortest Option PW pulse width is one millisecond.
  • The pulse width can only be specified as an integer millisecond value, so you cannot specify values like 2.5 milliseconds, but must use 2 or 3 milliseconds instead.
  • The pulse width will be limited to 50% of the total pulse period at the nominal full-scale frequency. For example, if you are using the standard 4.0 Hz full-scale frequency, then the total pulse period at full-scale is 250 milliseconds, so the pulse width will be limited to 125 milliseconds.
    • This limiting is applied independently for each pulse output channel, so if the full-scale frequencies are different for each channel, each may be limited to a different pulse width. This is most likely to occur in conjunction with Option DPO, where the P3 channel might be set to a higher pulse frequency. In this case, a constant pulse width will still be used for channel P3, but it may be shorter than the pulse width for channels P1 and P2.
  • If the WattNode Pulse meter is operating above nominal full-scale power, the pulse width ON (closed or conducting) period is limited to 80% of the total period (ON + OFF periods) to ensure that the pulse output doesn’t stay stuck continuously in the ON condition.
  • Option PW can only be used with custom frequencies up to 500Hz (Option Hz=500).
  • The maximum pulse width can be as large as 65 seconds if the full-scale frequency is low enough.

See Also