Sensoray 421 Bedienungsanleitung PDF herunterladen (Seite 17)

Sensoray Model 421 Instruction Manual Page 15

Unipolar-mode Transfer Function

As discussed earlier, A/D output codes are

represented as 12-bit unsigned integers in the

unipolar mode. Output values range from 0 at zero

volts input to 4095 at the positive full-scale input

voltage.

The following table shows the relationship between

input voltage and A/D output codes. A 0 to +10 volt

gain range (unity gain) is assumed for this

illustration.

Input Voltage Output Code

0.000V 000

2.441mV 001

4.998V 7FF

5.000V 800

5.002V 801

+9.997V FFF

Bipolar-mode Transfer Function

A/D output codes are formatted as 12-bit signed

two’s complement integers in the bipolar mode.

Output values range from -2048 at negative full-scale

input to +2047 at positive full-scale input voltage.

The following table shows the relationship between

input voltage and A/D output codes. A -5 to +5 volt

gain range (unity gain) is assumed for this

illustration.

Input Voltage Output Code

-5.000V 800

-4.997V 801

-2.441mV FFF

0.000V 000

+2.441mV 001

+4.997V 7FF

Input Connections

Each analog input channel makes two connections to

the 421 board. These two connections constitute a

differential input pair. The digitizer measures the

difference in voltage between the two inputs.

Note that the input common-mode voltage — the

voltage at either input relative to ISAbus five volt

return (GND) — should not exceed plus or minus 10

volts. Minor excursions beyond this limit will cause

inaccurate measurements. Significant excursions

may result in damage to digitizer circuitry. Refer to

the 421 specifications section for further details.

All analog input sources should be referenced to

ISAbus GND. If you are connecting an isolated

source (a source not referenced to GND), you should

tie one side of the source to GND. Since analog input

channels are true differential, it doesn’t matter which

side is connected to GND.

Connector Pinout

All differential analog inputs connect to 40-pin

header connector P2. This connector is shared by 421

analog input and analog output functions. The table

below describes that portion of P2 related to analog

input functions. Note that the GND signals are

related to both analog input and output functions.

Connector P2: Analog I/O

Pin Name Function

2 ADC0+ A/D channel 0 positive input

4 ADC0- A/D channel 0 negative input

6 ADC1+ A/D channel 1 positive input

8 ADC1- A/D channel 1 negative input

10 ADC2+ A/D channel 2 positive input

12 ADC2- A/D channel 2 negative input

14 ADC3+ A/D channel 3 positive input

16 ADC3- A/D channel 3 negative input

18 ADC4+ A/D channel 4 positive input

20 ADC4- A/D channel 4 negative input

22 ADC5+ A/D channel 5 positive input

24 ADC5- A/D channel 5 negative input

26 ADC6+ A/D channel 6 positive input

28 ADC6- A/D channel 6 negative input

30 ADC7+ A/D channel 7 positive input

32 ADC7- A/D channel 7 negative input

33,34,

38,39,

GND Analog common

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 26 27

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