ADC

The PXIe-4309 has eight simultaneously sampled 18-bit 2 MS/s successive approximation (SAR) ADCs.

SAR involves a binary search through all possible quantization levels before finally converging upon a digital output for each conversion.

The PXIe-4309 automatically detects compatible accessories or terminal blocks. The RSVD pins on the I/O connector provide power to the accessories and digital communication lines; this allows software to detect when accessories are inserted or removed. In addition, software automatically identifies the specific terminal block as well as accesses any calibration or scaling information associated with the terminal block.

Single Channel per ADC

The PXIe-4309 can sample eight simultaneous input channels up to 2 MS/s when only one channel per ADC is selected.

Multiple Channels per ADC

The PXIe-4309 can sample 32 input channels when multiple channels per ADC are selected. In this mode of operation, each ADC can scan through four independent input channels up to an aggregate sample rate of 400 kS/s. The following table shows the mapping of input channels to ADCs.

Table 6. AI Channels to ADC Mapping
ADC AI Channels
0 AI0, AI8, AI16, AI24
1 AI1, AI9, AI17, AI25
2 AI2, AI10, AI18, AI26
3 AI3, AI11, AI19, AI27
4 AI4, AI12, AI20, AI28
5 AI5, AI13, AI21, AI29
6 AI6, AI14, AI22, AI30
7 AI7, AI15, AI23, AI31

The signal conditioning circuitry of each ADC has a non-zero settling time when it changes the input multiplexer to scan through multiple channels.

The settling time increases as the aggregate sample rate decreases to allow for more settling time. This reduces settling and ghosting errors.