Omega Engineering DAQ-12 user manual Code

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.

J6

4 5 6

1 2 3

Bipolar

J6

4 5 6

1 2 3

Unipolar

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 =

Bipolar mode: input =

CODE

4096

CODE

2048

*

*

10V

GAIN

5V

GAIN

DAQ-12 Users Manual 13