User Manual

On Air Message Types 4-9
SmartPoint Module for the Elster A3 Meter ECMTM40000
4.8.6 Peak Demand Reading
32 bits, all of bytes 5-8. The peak demand reading is represented as a four byte floating point number
in W.
4.8.7 Phase A, B and C Meter Voltages
Three 8 bit fields containing meter line voltage readings of the voltage for all available phases at the
time of the meter reading. The values in the fields can be converted to voltage using the following
formula which provides voltages from 50 to 560 volts:
Voltage = Value*2 + 50
4.8.8 Compression Enabled History Samples
All bits of bytes 12-27 compressed using a Huffman Binary Tree compression algorithm. As many
History Sample bins as possible are packed into the remaining space in the on air message, up to 136
bins in the minimum case. Each history sample is stored as the difference from the last reading.
The Codex used to encode the histories is shown in the following table:
Scanning begins at bit 0 of byte 0 and goes to ms bit of byte 0 before rolling down to the ls bit of byte 1
on through the history buffer..
To decode, scan through the buffer counting consecutive 1’s. When a 0 is reached, that denotes the
end of the Key Bit Pattern. The number of consecutive ones indicates the specific symbol.
If the end of the buffer is reached before a complete valid symbol is reached, ignore that history value.
Key Bit Pattern
(binary)
History
Value
Required
Number of
Bits
Comment
001
10 1 2
110 2 3
1110 3 4
11110 4 5
111110 5 6
1111110xxxxx
6-37 11
If 0x7E is detected, the
next 5 bits + 6 = value
11111110xxxxxxxxxxxxx
38-8213 21
If 0xFE is detected, the
next 13 bits + 38 =
value
11111111
N/A N/A
End of usable history,
end history processing