National Instruments Deterministic Ethernet Expansion Chassis NI 9144 Manual de usuario descargar pdf (Pagina 31)

3. Select the 32-bit offset value (to be interpreted as a signed int) for a

particular range.

4. Use the above final coefficients and complete the following steps in the

quadratic equation to convert raw 16-bit data into scaled volts:

a. a0 = (f64(a0) * rangeGain) + rangeOffset

b. a1 = f64(a1) * rangeGain

c. a2 = f64(a2) * rangeGain

d. a3 = f64(a3) * rangeGain

5. Use the following formula with a3–a0 to obtain the scaled 16-bit value

in Volts.

x =signed un-scaled 16-bit data read from device:

Scaled 16-bit signed data in Volts = a3*x

+ a2*x

+ a1*x + a0

It is also possible to decode the raw data using only the offset and gain

values. For more information, refer to the NI 9201/9221 section of this

guide.

NI 9211

NI 9211 Scan List

The scan list is a simple list of channels to convert, in order. The NI 9211

has six channels total that can be measured:

• 0..3: Four input channels (always measured in a ±80 mV range)

• 4: One cold junction channel (always measured in a ±2.5 V range)

• 5: One auto zero channel (always measured in a ±80 mV range)

Table 18. NI 9211 Vendor Configuration Extensions

Index Sub Type R/W Description

0x2001 0 ARR:U32 — Scan List = 7

1 R Channels to

Convert = 1..6,

default = 6

2..7 R/W Channel Number

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 64 65

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National Instruments Deterministic Ethernet Expansion Chassis NI 9144 Manual de usuario Pagina 31