Fig. 3-3. The Principle Of Obtaining Adc Data (In Detail) - L-Card L-502-P-G-D-I User Manual

27
switching period. L-502 has, by default, that for n
the last one, during the switching period - this creates the greatest time for setting the signal after
switching (due to "idle" ADC conversion cycles), therefore the least stringent requirements are
imposed to the impedance of the signal source. On
default" for the logical channel 1: the first two counts are always discarded, and the third one is
used. But the real tasks of using multichannel ADCs do not assume that the impedances of the
signal sources are the same, and for channels with connected low-impedance sources it would be
good not to discard at least some of the ADC samples, but to use them for averaging the data,
thereby increasing the enable when measuring this channel. This possibility is provided in L-502
due to the fact that in every cell of the control table, besides the physical channel number, there is
also the averaging factor n
many counts of the ADC from the end of the switching cycle of this channel will be used to
averaging the data". Accordingly, n
beginning of the switching cycle of the given channel will be discarded", or "how many periods t
will be used to set the signal at the ADC input after switching".
For example, on
which means that for n
be used for averaging, and one first period is added to the time of signal establishment after
switching. For logical channel 3, all three samples of the ADC are used for averaging, and therefore
the minimum time is assigned here to establish a signal after switching.
Номер
ADC logical
логического
channel
канала АЦП
number
n =3
sw
Канал 1
Channel 1
Канал 2
Channel 2
Канал 3
Channel 3
Отброшенный отсчёт данных АЦП
Discarded ADC data sample
Момент сэмплирования одиночного отсчёта данных АЦП
Sampling time of a single sample ADC data
Моменты сэмплирования отсчётов данных АЦП и выдача усредненного отсчёта
Sampling timing of ADC data and output of averaged readout

Fig. 3-3. The principle of obtaining ADC data (in detail)

fig. 3-3
From
settling time for the first logical channel. This can be used, for example, by associating the first
logical channel with the physical channel to which the signal source is connected by the largest
impedance.
, by default, n
av
su
fig. 3-3
for navigational channel 2, n
=3 the result of the last two conversion periods in one switching phase will
sw
Кадр
Frame
t
k
n =3
k
1 2
n =1
av
n =2
su
n =2
av
n =1
su
t n
ref
it also follows that the set non-zero interframe delay actually increases the
> 1 all ADC readouts are flipped, except for
sw
fig. 3-3
, with n
= 1. Averaging factor n
av
= n - n means "how many ADC counts from the
sw av
Межкадровая
Interframe
задержка
delay
t
d
n =2
d
3 1
t
sw
n =3
av
=0
su
t
ch
3.3: Operation principle
=3, such conditions are set "by
sw
={1,2,...,128} means: "how
av
= 2 is installed in the control table,
av
Кадр
Frame
t
k
2 3
ref
Interframe
Межкадровая
задержка
delay
1