Omega Engineering DAQ-12 user manual Code

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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

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Contents 15,1*,1 WARRANTY/DISCLAIMER Manufacturer’s Address Manufacturers NameApplication of Council Directive Standards to which Conformity is DeclaredFor immediate technical or application assistance Servicing North AmericaServicing Europe Page Table of Contents Introduction List of Figures and Tables Installation DAQ-12 Specifications Analog to Digital Converter Jumper J1 ConfigurationDisable Pre-Scaler Enable Pre-Scaler Factory default Recommended Input Ranges and Gain Settings Code Voltage Unipolar Bipolar Code Digital to Analog ConvertersGain = Channel BipolarBase Address Digital Input/OutputClock Selection Internal Clock External Clock Start of Conversion Trigger Selection10. Jumpers J8 and J9 Configuration Dack Direct Memory AccessExternal Interrupt InterruptsExternal Connections Page Control Word Register Register DescriptionINT2 INT1 INT0 Description 3 A/D Converter Data Register Start of Conversion Register4 D/A Converter 0 Register Multi-Function Timer Register5 D/A Converter 1 Register Clock Rate Register low wordProgramming the 8254 Counter/Timer Counter 1 Clock rate register high word Version January 28
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