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Calmu3 (possibly Calmu3+) from Polymeters Response International. "The first microprocessor-based meter", using "FFT, rather than 'brute-force' DSP" [1]

I think I read somewhere that Calmu3 (minus the +) lacks CoP5 approval, but the picture in the manual shows the same as ours.

It may need calibration periodically, but that's probably up to the supplier.


  • Serial no: P99A01869
  • Part no: C3DBD0BC0SJ (3 phase direct, class 1 accuracy, lithium backup, C?)


Software with support


A later model, with a nice overview of available metrics.

Presumably ex-PRI consultant on Calmu meters

Serial protocol

1200bps ASCII, \r terminated

Equals symbols are shown on some variables, but presumably wouldn't fit for many. This seems to be consistent within each value, however.

'N', 's', 'u' or 'x' seem to be special-cased for some reason. If a valid index isn't provided for 'N' or 'x', the meter returns '\xff' with no '\r', so take steps to prevent this. If a valid index isn't provided for 'u', 'U\r' is returned. 's' always seems to return the same value.

Lowercase are always inverted and smaller than uppercase, suggesting they're from another perspective. Presumably 'u' just calls 'U', which is why it acts strangely.

Sampling seems to be live, so sampling more frequently will be more accurate.


F Frequency, updated per sample "F=50.138\r"
R (Real?) time "R=15:00:40\r"
S Serial number "SP99A01869\r"
s  ? related to 'B'? "s=", dword 0xa605019e, dword 0, "\r"
B[AVWvw]  ?

  • "BAA3123B"
  • "BV182B85"
  • "BW918D2F"
  • "Bv05B6CE"
  • "Bw01B525"

I[123] Current

  • "I1+15.230"
  • "I2+0.0000"
  • "I3-0.0300"

i[123] Current?

  • "i1-5.6300"
  • "i2-0.0000"
  • "i3-0.0100"

K[123AVW]  ?

  • "K1+2.0700"
  • "K2+0.0000"
  • "K3+0.0100"
  • "KA+2.0600"
  • "KV-1.3300"
  • "KW+1.6300"

L[123] Line current?

  • "L1+9.0200"
  • "L2+0.0100"
  • "L3+0.0200"

P[123]  ?

  • "P1+1.6400"
  • "P2-0.0000"
  • "P3+0.0000"

p[123]  ?

  • "p1-1.3400"
  • "p2+0.0000"
  • "p3-0.0100"


  • "Q1=0.769-"
  • "Q2=1.000+"
  • "Q3=1.000+"
  • "QA=0.787-"

U[AVWvw] Units

  • "UA=2631984"
  • "UV=0349470"
  • "UW=2549220"
  • "Uv=0177551"
  • "Uw=0000001"

u[AVWvw] Units (duplicate?)

  • "UA=2631986"
  • "UV=0349470"
  • "UW=2549221"
  • "Uv=0177552"
  • "Uw=0000001"

V[123] Voltage

  • "V1+236.75"
  • "V2+240.72"
  • "V3+242.45"



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