National Instruments SCB-68A User Manual

2-18 | ni.com
Chapter 2 Analog Input and Temperature Sensor Measurements
For best results, use the average of at least 100 readings to reduce the effects of noise;
typical absolute accuracies should then be about ±2 °C.
Open Thermocouple Detection
You can build open thermocouple detection circuitry by connecting a high-value resistor
between the positive input and +5 V. A resistor of a few MΩ or more is sufficient, but a
high-value resistor allows you to detect an open or defective thermocouple.
Note Refer to the Soldering and Desoldering Components on the SCB-68A section
of Chapter 1, Getting Started with the SCB-68A, for more information about adding
components and for soldering and desoldering instructions.
• Differential analog input open thermocouple detection—Use position A to 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 2-12. Differential Analog Input Open Thermocouple Detection
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