Filtering; Data Format - Data Translation DT9828 User Manual

Note: The USB LED, shown in
acquiring data.

Filtering

The DT9828 module multiplexes all enabled channels to a single 24-bit Delta-Sigma
analog-to-digital converter (ADC). The overall throughput rate is programmable to up to
600 Samples/s. The throughput rate determines the ADC data rate, internal filter response,
and noise. The Delta-Sigma ADC noise is inherently low at all sample rates, but sampling at
lower rates yields lower noise. Additional noise filtering is implemented in software by a
moving average filter, which may be enabled or disabled in software.
The software filtering options are described as follows:
• Moving average – (The default filter setting.) This filter type removes unwanted noise
from your measurements and provides a compromise of filter functionality and response
time. This filter can be used in any application.
This low-pass filter takes the previous 16 samples, adds them together, and divides by 16.
• None – No filter (raw data). Use this option when you want to acquire fast thermocouple
response times. The response time is determined by the ADC data rate. Higher
throughput rates (data rates) yield faster response times, but the increased bandwidth also
results in higher noise.

Data Format

If you specify a thermocouple type of None for a thermocouple input channel, a voltage
measurement is selected and the instrument returns a voltage value. For all other
thermocouple types, a temperature value, in degrees C, or one of the error constants,
described on page
In normal operation, one, 32-bit floating-point value is returned for each enabled channel. If
you enable the capability of returning CJC data in the data stream, described on
floating-point values are returned in the data stream for each enabled analog input channel.
The first value in the pair represents the temperature (or voltage) of the channel; the second
value in the pair represents the CJC temperature (in degrees C) for that channel.
If the digital input port is in the channel list, that 4-bit value (value 0 to 15) is returned as float.
Note: The Input FIFO stores up to 1024 samples.
Figure 3 on page
61, is returned.
26, blinks amber while the module is
Principles of Operation
page 61, two
65