National Instruments DAQ M Series - Manual (Page 27)

Chapter 4 Analog Input
© National Instruments Corporation 4-3 NI 6236 User Manual
M Series devices use a calibration method that requires some codes
(typically about 5% of the codes) to lie outside of the specified range. This
calibration method improves absolute accuracy, but it increases the nominal
resolution of input ranges by about 5% over what the previous formulas
would indicate.
Table 4-1 shows the input range and resolution supported by the NI 6236
devices.
Connecting Analog Current Input Signals
When making signal connections, caution must be taken with the signal
voltage levels going into the device. There are two types of connections that
can be made.
Method 1
Method 1, shown in Figure 4-2, connects AI + and AI – inputs at a voltage
level with respect to AI GND. Verify that the voltage levels on the AI + and
AI – side do not exceed the common-mode input range of ±10 V.
Common-mode input range is the voltage input range with respect to
AI GND (AI + versus AI GND or AI – versus AI GND).
Table 4-1. Input Ranges for NI 6236
Input Range
Nominal Resolution Assuming
5% Over Range
±20 mA 640 nA