Chapter3 HardwareOverview
©NationalInstruments Corporation 3-3 NI6013/6014 User Manual
Input Range
The NI 6013/6014 has a bipolar input range that changes with the
programmed gain. Each channel may be programmed with a unique gain
of 0.5, 1.0, 10, or 100 to maximize the A/D converter (ADC) resolution.
With the proper gain setting, you can use the full resolution of the ADC
to measure the input signal. Table 3-2 shows the input range and precision
according to the gain used.
Scanning Multiple Channels
Thedevices can scan multiple channels at the same maximu mr atea s their
single-channelrate; however, pay careful at tention to the settling times for
each device.No extra settling time is necessary between channels as long
asthe g ain is constant and source impedances are low. Refer to
Appendix A, Specifications, for a complete listing of settling times for each
ofthe d evices.
When scanning among channels at variousgains, the settling times may
increase.When the PGIA switches to a higher gain, the signal on the
previouschannel may be well outside the new, smaller range. For instance,
suppose a 4 V signal is connected to channel 0 and a 1 mV signal is
connected to channel1, and suppose the PGIA is programmed to apply
again of o ne to channel 0 and a gain of 100 to channel 1. When the
multiplexerswitches to channel 1 and the PGIA switches to a gain of 100,
the newfull-scale range is ±50 mV.
The approximately 4 V step from 4 V to 1 mV is 4,000% of the new
full-scalerange. It may take as long as 100 µs for the circuitr y to settle to
1 LSB after such a large transition. In general, this extra settling time is not
needed when the PGIA is switching to a lowergain.
Table3-2. MeasurementPre cision
Gain Input Range Precision1
0.5 –10 to +10 V 305.2 µV
1.0 –5to+5V 152.6µV
10.0 –500 to +500 mV 15.3 µV
100.0 –50 to +50 mV 1.53 µV
1Thevalue of 1 least significant bit (LSB) of the 16-bit ADC; that is, the voltage increment
correspondingto a change of one count in the ADC 16-bit count.
Note:RefertoAppendixA,Specifications,for absolute maximum ratings.