This RTD HAT is using two ADS1248, 24 bit Delta-Sigma A/D converters and can achieve up to 0.01 °C accuracy. Each converter can read four 3-wire RTD-100 thermistors. The interface to the converters is implemented with a 32 bit STM32F030 processor which receives commands from Raspberry Pi via the I2C interface. All RTD channels can be read individually or simultaneously. Field calibration is possible using a precision 100 ohms resistor. Separate 3.3V power supplies for analog and digital components assure increased accuracy.

STACKABILITY

Since the HAT specifications provide for a single EPROM address per HAT, a true HAT cannot be stacked. In a non-HAT configuration, Mega-RTD can be stacked up to eight levels, for a total of 64 RTD Data Acquisition Channels. The stack level has to be selected with on-board jumpers.

ON-BOARD HARDWARE WATCHDOG

After developing our HAT HARDWARE WATCHDOG, we found out that this is a desirable feature and we decided to include it in most of our boards. The Mega-RTD board can be used for any mission-critical application, with the peace of mind that if Raspberry Pi locks up, the watchdog will perform a 10 second power cycle and reboot it.

3D PRINTED ENCLOSURE

We designed an enclosure which you can print yourself, assuming of course you have a 3D printer. The enclosure consists of a bottom plate which holds the Raspberry Pi and can be mounted on a DIN-Rail using standard brackets, the Raspberry Pi frame, followed by the Mega-RTD frame and a top. Up to 8 Mega-RTD's can be housed in the same enclosure by printing alternate frames to permit mounting the screws.

Software including command line and Python drivers. and A NODE-RED Data Acquisition Example can be downloaded from GitHub. (https://github.com/SequentMicrosystems/rtd-rpi)

The project is currently on KICKSTARTER