VTI Instruments EX1000A, Руководство пользователя

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EX10xxA Programming 103
Example: This code block configures channels 0 through 4 for a 4 Hz filter and channels 5 through
8 for a 500 Hz filter.
ViInt32 low_channels[5] = { 0, 1, 2, 3, 4 };
vtex10xxA_set_filt_freq(vi, low_channels, 5, 4.0);
ViInt32 high_channels[4] = { 5, 6, 7, 8 };
vtex10xxA_set_filt_freq(vi, high_channels, 4, 500.0);
The current hardware filter assignment for any channel is queried with the vtex10xxA_get_filt_freq
query.
C
ONFIGURE THE
FIFO
The vtex10xxA_set_fifo_config function is used to set the data format and overflow behavior of
the FIFO memory. By default, the data returned during data retrieval is limited to the input channel
readings and the absolute time of scan initiation. While measured with every scan, the CJC
temperature values are not returned unless enabled to do so. Reported CJC temperatures are always
in units of ºC, regardless of the units of the channel readings. In addition, the returned data can be
enabled to include delta timestamps per channel. Specifically, the timestamp represents the time, in
increments of 100 ns, between the specific channel measurement and the scan initiation time.
By default, the channel readings are returned with units of ºC. Optionally, the units can be set to ºF.
This setting has no effect on the reported CJC data or data for input channels that are configured for
an EU conversion of mV.
In addition to data formatting, this function is used to specify the system behavior if the reading
buffer fills to its maximum capacity during scanning. With blocking mode enabled, additional
readings are discarded, leaving the contents of the buffer intact. With blocking mode disabled, the
buffer becomes circular, in that additional readings overwrite the oldest readings.
The current FIFO configuration is queried with the vtex10xxA_get_fifo_config function.
NOTE Regardless of their enabling, the CJC temperature and delta timestamp information is not accessible
through the
vtex10xxA_read_fifo function. They are available through the streaming interface, and
the parameter settings apply for it.
C
ONFIGURE THE
L
IMIT
S
YSTEM
The EX10xxA features two sets of programmable limits. These limits, termed limit set 0 and limit
set 1, are programmable on a per channel basis. Manipulation of the limit set values is slightly
different for each limit set, as limit set 0 offers enhanced functionality.
By default, the values in limit set 0 are set automatically, based on the EU conversion and units
selection for each channel. Specifically, the upper and lower limit values are set to the upper and
lower values of the EX10xxA measurement range, as specified in Table 3-2. For example, if input
channel 0 is configured for an E type conversion and a units selection of ºC, its upper and lower
limit values will be +900 and -200, respectively. To override the automatic setting and set the values
manually on a per channel basis, manual control must first be enabled with the
vtex10xxA_set_limit_set0_manual function. A channel’s manual entry control can be set
regardless of its inclusion in the scan list, and multiple channels can be configured within one
function. However, each unique control value must be set with a separate function.
Once enabled for manual entry, a channel’s limit set 0 values are set with the
vtex10xxA_set_limit_set0 function. A channel’s limit values can be set regardless of its inclusion
in the scan list, and multiple channels can be assigned to the same limit values within one function.
However, each unique combination of limit values must be set with a separate function.
Example: This code block configures channels 0 through 4 for manual limit values of 0 and 100.