Programming instructions

© National Instruments Corporation 18-1 DAQ Hardware Overview Guide
18
NI 435 X Devices
This chapter contains overview information on the NI 435X devices,
including the NI 4350 for ISA, USB, and PCMCIA, and the NI 4351 for
PCI and PXI.
For more detailed descriptions of the hardware functionality and
specifications, see the NI 4350/4351 User Manual. Also, the 435X
instrument driver software documentation contains detailed information on
how to write programs to control the 435X device for making
measurements.
NI 435X devices are designed especially for data logging applications and
feature accurate DC voltage. This family of devices can also provide
thermocouple measurements as well as resistance temperature detector
(RTD), thermistor, and ohm measurements using the built-in precision
current source. The ultra-low leakage construction, in addition to analog
and digital filtering, gives the 435X devices excellent resolution, accuracy,
and noise rejection.
You can reference your floating voltage signal by using
software-programmable ground-referencing, without compromising
the measurement, even if the signal is ground-referenced.
Software-programmable open-thermocouple detection enables you to
quickly detect a thermocouple, which may have broken before or
during measurement. The current source supplies 25 µA for measuring a
maximum resistance of 600 kΩ. NI 4351 also has a 1 mA current source
for providing excitation to resistive sensors such as RTDs. In addition,
the 435X devices have TTL-compatible digital I/O for monitoring TTL
level inputs, alarms, and external device interfacing.
NI 435 X Device Analog Input
The NI 4350 for PCMCIA has eight differential analog channels
numbered 0 through 7, and the NI 435X for ISA, USB, PCI, and PXI has
16 differential channels numbered 0 through 15. The analog input channels
are multiplexed into a 24-bit sigma-delta ADC. All analog channels have a
low-pass filter to reject high frequency noise. Every channel has two switch
settings: ground-referencing and open-thermocouple detection. If you