National Instruments NI 6013 User Manual

Also see for NI 6013: Note to Users

Contents

National Instruments NI 6013 User Manual Manual pdf 23 page image

Chapter 3 Hardware Overview© National Instruments Corporation 3-3 NI 6013/6014 User ManualInput RangeThe NI 6013/6014 has a bipolar input range that changes with theprogrammed gain. Each channel may be programmed with a unique gainof 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 ADCto measure the input signal. Table 3-2 shows the input range and precisionaccording to the gain used.Scanning Multiple ChannelsThe devices can scan multiple channels at the same maximum rate as theirsingle-channel rate; however, pay careful attention to the settling times foreach device. No extra settling time is necessary between channels as longas the gain is constant and source impedances are low. Refer toAppendix A, Specifications, for a complete listing of settling times for eachof the devices.When scanning among channels at various gains, the settling times mayincrease. When the PGIA switches to a higher gain, the signal on theprevious channel 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 isconnected to channel 1, and suppose the PGIA is programmed to applya gain of one to channel 0 and a gain of 100 to channel 1. When themultiplexer switches to channel 1 and the PGIA switches to a gain of 100,the new full-scale range is ±50 mV.The approximately 4 V step from 4 V to 1 mV is 4,000% of the newfull-scale range. It may take as long as 100 μs for the circuitry to settle to1 LSB after such a large transition. In general, this extra settling time is notneeded when the PGIA is switching to a lower gain.Table 3-2. Measurement PrecisionGain Input Range Precision10.5 –10 to +10 V 305.2 μV1.0 –5 to +5 V 152.6 μV10.0 –500 to +500 mV 15.3 μV100.0 –50 to +50 mV 1.53 μV1 The value of 1 least significant bit (LSB) of the 16-bit ADC; that is, the voltage incrementcorresponding to a change of one count in the ADC 16-bit count.Note: Refer to Appendix A, Specifications, for absolute maximum ratings.