Omega-engineering DAQ-12 Manual do Utilizador descarregar pdf (Página 13)

The final stage of the A/D converter circuit is the A/D converter IC. The converter must be

configured for unipolar or bipolar input voltages as shown in Figure 2-3. When configured

for unipolar operation, the analog input multiplied by the gain setting must be in the range of

0 volts (analog ground) to +10 volts. When configured for bipolar operation, the analog

input multiplied by the gain setting must be in the range of -5 volts to +5 volts.

Bipolar

1 2 3

4 5 6

Unipolar

1 2 3

4 5 6

Figure 2-3. Jumper J6 Configuration

WARNING: The user must ensure that the maximum input voltage multiplied by the

amplifier gain does not exceed the range of 0 to +10 volts for unipolar operation or -5 to

+5 volts for bipolar operation.

Although the A/D converter produces 12-bit digital 'codes' to represent the input voltage, the

DAQ-12 converts these 'codes' into standard 16-bit signed integer values before returning

them to the PC. When the A/D converter is configured for unipolar operation, the DAQ-12

returns values in the range of 0 to 4095. When configured for bipolar operation, values in the

range of -2048 to +2047 are returned.

In order to calculate the actual input voltage from the value provided by the DAQ-12, the user

must know the configuration (unipolar / bipolar) and the gain setting used to acquire the

data. Given this information, the input voltage can be calculated using the following

equations:

Unipolar mode: input = *

CODE

4096

10V

GAIN

Bipolar mode: input = *

CODE

2048

GAIN

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Omega-engineering DAQ-12 Manual do Utilizador Página 13