Casella CEL CEL-393 - Manual (Page 36)

L Tm3 & L Tm5
The 'taktmaximal' results are required by certain West German meas-
urement protocols. These values are calculated respectively via a 3 and
5 second (takt) maximum hold gate, integrated assuming the maximum
had been present for the complete period, and then time averaged in the
same manner as the L
eq results.
The measurements are continually in progress, and will be seen to
update once per time period "takt" (3 and 5 sec). The maximum duration
permissable without the data registers overflowing for an L
Tm measure-
ment is 64 hours. In order to provide correct L AFTm results, as required
by the standards, the fast time constant and A-weighting must be
selected.
Some measurement protocols (for example gunfire) call for the maximum
weighted impulse period average L
A I Tm , and in these cases the impulse
I time weighting should be selected.
SEL
The parameter was previously known as L AX , and is defined as the event
energy averaged over one second. The events are determined as signals
going 20dB above the measurement range datum and returning below
it again for at least 4 seconds. It is only valid in the event mode (infinite
period time) with the most recent or current event during any one
measurement being available for display by key sequence 7F.
However, individual events are separated in the memory, and these may
be indexed at any time during a measurement to obtain the SEL,
maximum, duration and start time of each. In the other memory modes,
no current mode SEL is calculated, so in these situations key sequence
7F has no meaning.
Three L n Values
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