24/7 Data Acquisition Wildcard Users Guide

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Connecting to the 24/7 Data Acquisition Wildcard

To start using the 24/7 Data Acquisition Wildcard, follow these simple steps:

1. If you are using a Wildcard Carrier Board and QED Board, connect the Wildcard Carrier Board to the QED Board as outlined in the "Module Carrier Board Users Guide". If you are using another controller the WildCard plugs directly into the controller.
2. With the power off, connect the 24/7 Data Acquisition Wildcard to the Wildcard Carrier Board or to your Controller by connecting the Module Bus of the 24/7 Data Acquisition Wildcard (labeled Module Bus) to Module Port 0 of the Wildcard Carrier Board (located below the QED Digital I/O header and to the right of Module Port 1) or of your controller. Caution: The 24/7 Data Acquisition Wildcard or your controller can be permanently damaged if the connection is done incorrectly.
3. Be sure the jumper shunt for J1 is not installed on the 24/7 Data Acquisition Wildcard. With the jumper shunt not installed, the reference voltage for the analog to digital converter is set to 2.5 volts.
4. Be sure the jumper shunts for J2 and J3 are not installed on the 24/7 Data Acquisition Wildcard. With both jumper shunts not installed, the address of the module is set to 0.
5. Turn on the power to the QED Board or other controller; this automatically powers the Wildcard Carrier Board and the 24/7 Data Acquisition Wildcard.
6. Connect Field 3 (Pin 18) to AGND (Pin 17). This is most easily done if you use a Screw-Terminal WildCard to provide screw terminal connections for the Field Header.
7. Connect Field 2 (Pin 16) to a known voltage between 0 and 2.5 Volts.
8. Run the demonstration program as described in the readme.txt file on the distribution diskette. This program:
• Initializes the module
• Configures the module to use the on-board reference voltage
• Calibrates and configures channel CH_2_3
• Takes one 24 bit bipolar sample with a gain of one
• Prints the voltage to the terminal
• Returns a success flag.

Once the hardware and software are properly configured, you can obtain high-resolution samples with the pre-coded high level driver routines.

Hardware

The 24/7 Data Acquisition Wildcard consists of:

• the AD7714, a high resolution signal conditioning analog to digital converter;
• two low-power, low-dropout regulators that supply power for the digital and analog circuitry;
• a high precision voltage reference;
• 12 precision analog switches to electrically protect the analog inputs of the A/D converter chip from excessive voltage;
• three general purpose digital inputs; and,
• seven analog input channels.

On-Board Reference

The 24/7 Data Acquisition Wildcard has an on-board 2.5 V voltage reference that is accurate to +/- 0.005 V. This reference is available for use by sensors requiring a reference or producing a proportionate output. It can supply up to 10 ma. The reference voltage is available on pins 7 (REF+) and 13 (REF-) on H2 of the 24/7 Data Acquisition Wildcard. To use the on-board reference voltage for analog to digital conversions call Use_Onboard_Ref. You can also use your own external reference voltage by connecting an external voltage to pins 9 (FDREF+) and 11 (FDREF-) of H2 and calling Use_External_Ref. Be sure that FDREF+ is always greater than FDREF- for correct operation of the analog to digital converter. The recommended reference voltage for the analog to digital converter is 2.5 V. The 24/7 Data Acquisition Wildcard is functional with external reference voltages from 2.5 volts down to 1 volt but with degraded performance as the output noise will, in terms of LSB size, be larger. If jumper J1 is installed, the reference voltage that appears on the REF+ output pin is changed to 3.0 V, which exceeds the specified reference input voltage by 0.5 volt. DO NOT USE THIS 3.0 VOLTS AS A REFERENCE VOLTAGE! That is, if jumper J1 is installed do not call Use_Onboard_Ref or connect REF+ and REF- to FDREF+ and FDREF-. The 3.0 V option is useful for powering external sensors and transducers and provides up to 10 mA of current.

Figure 1 shows a typical application of 3.0 V option with an RTD.

Fig.1: Typical Application of the 3.0V Option

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