National Instruments SCB-68A User Manual

© National Instruments | 2-19
NI SCB-68A User Manual
• Single-ended analog input open thermocouple detection—Use position A for one
channel and C for the next channel when you connect a high-value resistor between the
positive input and +5 V. Leave the 0 Ω resistors at positions F and G in place for each
channel used. Refer to Table 2-1 for component positions for all analog input channels.
Figure 2-13. Single-Ended Analog Input Open Thermocouple Detection on AI <i>
If the thermocouple opens, the voltage measured across the input terminals rises to +5 V, a value
much larger than any legitimate thermocouple voltage. You can create a bias current return path
by using a 100 kΩ resistor between the negative input and AI GND.
Thermocouple Input Filtering
To reduce noise, you can connect a simple one-pole RC lowpass filter to the analog inputs of the
SCB-68A. Refer to the One-Pole Lowpass RC Filter section for more information.
AIi
AIi+8
y
SCx
E
A
F
G
B
C
D
+
+
+
–
+
5 V AI GND
+
5 V AI GND
AI i
AI i
+
8

National Instruments SCB-68A Specifications

General

Brand	National Instruments
Model	SCB-68A
Category	Cables and connectors
Language	English