16-Channel 24-Bit ADC Data Acquisition Shield for Arduino
The ARD-LTC2499 is an Arduino compatible shield that contains a Linear Technology LTC2499 24-bit ADC coupled with an LT6654 precision voltage reference. It is capable of converting 16 single-ended channels, 8 differential channels, or any other combination. In addition to measuring voltage, the ADC can interface directly to a variety of sensors including strain gauges, thermocouples, and current shunts. The onboard EEPROM can be used to store calibration and configuration information directly on each ARD-LTC2499 board. A 6-byte EUI-48-compatible globally unique ID number is also provided. The ARD-LTC2499 can be used with other Arduino shields to make a simple, yet very accurate, data acquisition system.
Note: The normal ARD-LTC2499 is not compatible with Arduinos using 3.3V I/O on the I2C lines, such as the Due, Zero, etc. This is because the LTC2499 requires a 5V supply to deal with the 4.096V reference voltage, making it incompatible with 3.3V I2C. A 3.3V compatible version is available here.
- 24-bit delta sigma ADC
- 4.096V precision voltage reference
- 16 single-ended channels, 8 differential channels, or any combination
- Optional onboard 5V linear regulator provides clean power to the ADC and reference
- 128 bytes of onboard EEPROM for storing configuration or calibration values
- Read-only 6-byte EUI-48-compatible globally unique ID
- Arduino form factor and software library
- I2C interface
2.7"(L) x 2.1"(W)Input Voltage Range:
0V to VREF/2 (single-ended)
-VREF/2 to +VREF/2 (differential)
The complete gEDA design files are available on GitHub.
Note: Arduino is a registered trademark of Arduino AG.
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News & Application Notes
Direct Thermocouple Measurement with the ARD-LTC2499
One of the unique uses of the ARD-LTC2499 24-bit Analog to Digital Convert Shield is to measure thermocouples directly. Conventional solutions for digitizing thermocouples use a MAX31855 or MCP9600 to convert the voltage to a usable temperature, but these solutions need one part for each thermocouple sensor, and the part is tied specifically to the type of thermocouple being used. By using the LTC2499 to measure the thermoelectric voltage directly, we can measure up to 8 thermocouples per board, and because all of the conversion is done with math on the host processor, you can have any mix of thermocouple types that you want. It’s remarkably easy to do, and I’ll show you how just how easy it is to get started.
Is the ARD-LTC2499 as Accurate as an Agilent 34401A?
The ARD-LTC2499 was designed from the beginning with the intent to get as close to perfect accuracy as one could with an out-of-the-box Arduino Shield, while still keeping the cost affordable for mere mortals like us.Â We chose one of the best 16-channel ADCs on the market and matched it up with a high-performance voltage reference.Â To see what the accuracy really was, I borrowed Nathan’s 34401A meter and put them both to the test.
Solar Car Teams
Most Iowa Scaled Engineering products are designed using surface mount components to keep costs low (smaller boards) and allow the use of a wider range of components.Â One of the primary tools in the assembly process is an oven to reflow the solder paste that attaches the components to the PCB.Â Originally, we developed our reflow recipe using a thermocouple, a multimeter with temperature capability, and a stopwatch.Â This has worked quite well.Â Now, as a practical application of the ARD-LTC2499 Arduino shield, we take a closer look at the reflow process.
Measuring Supply Current Accurately
The current measurement mode in most multimeters is sufficient for many applications.Â However, when measuring the supply current of loads that draw current infrequently in small bursts, it becomes difficult to measure the real, average current consumption accurately due to the slow sample rate of the multimeter.Â Many wireless telemetry nodes present exactly such a situation and calculating expected battery life relies on an accurate measurement.Â Fortunately, physics comes to our rescue (along with a few widgets to make things easier…).
Data Acquisition Arduino Shields
After developing several products focused on data acquisition, like the MRBW-RTS and a few currently in development like the MRB-DCCM (DCC Meter) and MRBW-DAQ (Data Acquisition node), we realized some of the ICs used in those designs would be useful on their own.Â To enable rapid development with these ICs, a series of ArduinoTM shields was created allowing you to easily implement a wide variety of data acquisition applications.