Chapter 2
Operating the NI 435x Device
2-2
ni.com
Choosing a Range
The volts mode has six bipolar input ranges: ±625 mV, ±1.25 V, ±2.5 V,
±3.75 V, ±7.5 V, and ±15 V.
The 4-wire ohms mode has six corresponding input ranges when used with
the built-in 25
µΑ
current source: 25 k
Ω
, 50 k
Ω
, 100 k
Ω
, 150 k
Ω
,
300 k
Ω
, and 600 k
Ω
, and 625
Ω
, 1.2 k
Ω
, 3.75 k
Ω
, 7.5 k
Ω
, and 15 k
Ω
with the built-in 1 mA current source on the NI PXI-4351 or NI PCI-4351.
Choose the smallest range for the best measurement results
.
When
scanning multiple channels, the NI 435
x
uses a single range, which is the
widest range of any channel in the scan list.
Note
With VirtualBench-Logger or the MAX Create New Channel Wizard, you can
specify the range based on the sensor type in engineering units appropriate to the sensor.
This sensor range is used to automatically set the actual hardware range.
Choosing a Reading Rate
The
reading rate
is the rate at which the NI 435
x
takes a new measurement.
This rate has a direct relationship with the digital filter built into the ADC
used in the NI 435
x
.
The digital filter has the characteristics shown in Figure 2-1. You can set the
frequency of the first notch of this filter to 10 Hz, 50 Hz, or 60 Hz. Setting
the notch filter at one of these frequencies rejects any noise at that
frequency as well as at all of its multiples.
Figure 2-1.
Digital Filter Characteristics for 10 Hz Setting
0
–20
–40
–60
–80
–100
–120
Gain (dB)
Frequency (Hz)
0
10
20
30
40
50
60