PT100

24 Bit 4 Probe Measurement Board for RTDs

Ultra precise, portable, 24bit ADC for 4 probe kelvin sensing. sub milli ohm standard deviation. adjustable current range from 1uA to 1mA. Works in web browsers! PC/Android.

Scrolling resistance measurement plot. 300 micro ohm standard deviation @ 100 ohms

Rated for the full range of PT100 from -200 to 850C .

Powered by USB. Low power operation. Includes Python library

A four-wire PT100 you can open in the browser

Plug this board into a USB port(Computer/Androids) and use it as a live temperature and resistance meter. The page shows the reading, draws real time graphs, and has raw data downloads!

A PT100 is a small platinum sensor whose resistance follows temperature (Callendar-van Dusen Equation) . At room temperature it sits near 100 ohms, and a degree of temperature is only a fraction of an ohm. On this board, a 100 ohm measurement settles with a standard deviation under 500 microohms.

Four probe setup

The sensor is wired with four leads. Two carry the excitation current, and two only sense the voltage across the platinum. The resistance of the cable then stays out of the answer, which matters once the cable is long or the change you care about is tiny. The same current also passes through a reference resistor on the board, so the reading is a comparison between the sensor and that known resistor. Temperature follows the usual platinum curve. To further reduce noise, don't forget to use twisted pairs !

A 24-bit converter sits on the board. You can pick the reference, the current, and how fast to sample, then record.

What can you do with it

Web Browser talks to the board directly. Press connect and the live temperature and resistance appear at the top of the page. Record starts a log. Pause, clear, and save a CSV are right there. The graph can show temperature, resistance, or the raw converter code. Drag to look back, scroll to zoom, and double-click when you want it to follow the newest samples again.

The window you are looking at also reports how many points are on screen, their average, and the standard deviation, in ordinary units. That is the same kind of number as the sub-500-microohm result at 100 ohms: a plain measure of how still the reading is.

A small colour LED on the board shows whether it is powered, connected, or talking to the page. A colour button next to the theme switch opens a wheel if you want to set it yourself coz you're just bored.

It is a compact instrument for watching a PT100: four-wire, quiet at 100 ohms, and ready as soon as the cable is plugged in.

On Board Inter Digitated Electrodes

The board includes 4 sets of interdigitated electrodes with 100 micron line spacing for measurement of liquid sample resistivity. Small solder jumpers can be shorted to connect the 4 probe system to these.