For DC recording it is possible to select a writing speed of 250 mm/s on the Type 2306,
and 1 000 mm/s on the Type 2307. In practice set as high a value as possible without
introducing instability.
Averaging Time
TA (s)
0,1 0,3 1
3
10
30 100 300
Paper speed for
DC recording
(mm/s)
10
3
1 0,3 0,1
0,03 0,01
0,003
The writing speed for AC recording is determined by the averaging time required. Sui-
table writing speeds can be selected from the shaded portion of Fig.5.2, which is valid
for both types of Level Recorders.
5.3.4. Paper Speed
The paper speed should be chosen so that the Recorder pen can attain the correct level
for each measuring band, and remain at that level for a while before the next filter band
is selected.
Normally, for DC recording it will be the rate of fall of the detector, with maximum
8,7 dB per selected averaging time, that limits the sweep rate. Table 5.2 gives suitable
paper speeds for the normal range of averaging times, based on the assumption that the
time required to sweep over a bandwidth is equal to five averaging times. With the Type
1618, normally the step between filters will be attained in less than 2 mm (i.e. 40% of
the bandwidth), and even in the very worst case of a single sinusoidal component lo-
cated between two filters, it will be reached with 75% of the bandwidth.
710409
Tab le 5.2. Paper speeds for DC recording
Where the spectrum is known to be relatively flat with a maximum fall less than 5 dB be-
tween adjacent filter bands, it is possible to increase paper speed by one step (i.e. a fac-
tor of approximately 3). The time taken to sweep over one bandwidth will be approxi-
mately 1,6 times the averaging time, which is about the minimum required for the detec-
tor to respond, even on peaks.
The same basic considerations apply for AC recording, except that it will be the writing
speed rather than the averaging time which determines how rapidly the recording pen
can respond to a new level. Table 5.3 gives suitable paper speeds for the range of writ-
ing speeds available. Once again these may be increased by one step when the spec-
trum is known to be relatively flat.
Writing speed (mm/s)
(100 mm paper)
4 8-16 31,5 — 50
Paper speed for AC
recording (mm/s)
0,1
0,3
80 — 125
200 — 2000
1
3 10
Tab le 5.3. Paper speeds for AC recording (Type 2307)
170410
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