©
National Instruments Corporation
2-1
2
Operating the NI 435
x
Device
This chapter describes how to use the NI 435
x
device and includes
operation tips on taking measurements with temperature sensors such as
thermocouples, RTDs, and thermistors, as well as measuring voltages and
resistances.
Caution
Refer to the
Read Me First: Safety and Radio-Frequency Interference
document
before removing equipment covers or connecting/disconnecting any signal wires.
Warming up the NI 435
x
Device
To minimize the effects of thermal drift and to ensure the specified
accuracy, allow the NI 435
x
device to warm up for at least 10 minutes after
startup before taking measurements. To maximize the relative accuracy of
measurements, take all measurements after the NI 435
x
device warms up
for about 30 minutes.
Choosing a Measurement Mode
Each analog input channel can be configured in two possible measurement
modes—the volts mode or the 4-wire ohms mode. Use the volts mode for
thermocouple and voltage measurements and the 4-wire ohms mode for
RTD, thermistor, and resistance measurements using the built-in current
source to provide excitation for the resistive sensors. In the 4-wire ohms
mode, the software returns the resistance value by dividing the voltage
measured by the value of the current source stored onboard.
Note
VirtualBench-Logger, the NI 435
x
instrument driver, and the MAX Create New
Channel Wizard select the measurement mode automatically, depending on the sensor type
you specify.