Spectrum Controls 1746sc-NI8u - Manual (Page 56)

44 SLC 500 ™ Universal Analog Input Module
For example, if channel one is configured as a thermocouple type when
the CJC breaks in an open-circuit condition, if open-circuit detection is
disabled, the data word will remain unchanged. If the circuit selection is
set at minimum, the data word will be set to the low scale value for the
range and format.
Select Temperature Units (Bit 10)
The temperature units bit lets you select temperature engineering units for
thermocouple, RTD, and CJC input types. Units are either degrees
Celsius (°C) or degrees Fahrenheit (°F). This bit field is only active for
thermocouple, RTD and CJC input types. It is ignored when millivolt or
current inputs types are selected.
Select Channel Filter Frequency (Bits 11 and 12)
The channel filter frequency bit field lets you select one of four filters
available for a channel. The filter frequency affects the channel update
time and noise rejection characteristics. A smaller filter frequency
increases the channel update time, but also increases the noise rejection
and channel resolution. A larger filter frequency decreases the noise
rejection, but also decreases the channel update time and channel
resolution.
• 250 Hz setting provides minimal noise filtering.
• 60 Hz setting provides 60 Hz AC line noise filtering.
• 50 Hz setting provides 50 Hz AC line noise filtering.
• 10 Hz setting provides both 50 Hz and 60 Hz AC line noise filtering.
When a CJC input type is selected, this field is ignored. To maximize the
speed versus resolution trade-off, CJC inputs are sampled at 60 Hz.
Select RTD Type (Bit 13)
The selection for RTD or resistance type is only valid for channels 4
through 7, and should be set to zero for channels 0 through 3.
If the Input Type selection defines an RTD or resistance type, then the
wire type also needs to be specified. The universal module converts the
RTD or resistance type input data differently according to whether the 2
or 4 wire method is used, or the 3 wire method is used.
Select Auto-Calibration Disable (Bit 14)
The auto-calibration disable bit allows you to disable periodic auto-
calibration. Set this bit on any enabled channel to disable auto-calibration
for all channels. Clear this bit on all enabled channels to enable auto-
calibration on all channels.