The Arduino used is the Nano Every. It has been chosen because of its formfactor. It can be powered by any voltage in the range of 12 to 24 volts. A dc/dc converter (TSR 1-2490) steps that down to 9 volts. We even spend two identical 2.1 mm dc sockets, so that daisy-chaining is not a problem.

The Arduino handles the usb traffic, the oled displays any value and a rotary encoder (when equipped) allows for updating any settings.

The I2C version is equipped with a d-sub connector to handle any sensor using serial data transmission. It can supply power (5 volts, 9 volts) and also can handle an alarm line (when sensor has this option).



Not much inside ...

PIN  SIGNAL  1  + 5 V, 250 mA  2  SDA  3  GND  4  GND  5  SCL  6  GPIO, TTL  7  + 9 V, 250 mA  8  + 9 V  9  ALARM, OC

Using an RS232 cable for an I2C connection was originally not foreseen (by the inventors of I2C, Phillips™) but it works nice if the length is kept under 1.99 m. If longer distances are necessary to be bridged, it might help to slow down the transmission on the SCL and SDA lines. This connection was chosen, because the hardware is widely available and therefore no GPIB budget is necessary. The Pinout is compatible to the (unpublished) Envico System used in our labs, therefore the sensors are interchangeable. The sensors use always the male connector, as they are somehow considered the source of the data. The basestation uses female connectors.

And yes, we use 5 Volt logic levels for I2C. If a sensor wants 3.3 Volt, a level shifter as well as a voltage regulator shall be added to the sensor.

Every sensor has an Eeprom (e.g. 24C01) to hold information such as serialnumber, type of sensor or calibration values (if necessary). This means, that they have to be programmed upon first use, but an exchange (something that physicists often do) is smoothly possible. And the basestation always knows how to get the measurement values out of them :-)

Remote Control with e.g. HTerm 0.8.5 from Tobias Hammer


These commands should work with or without any sensor. If some future sensors require extended commands, they shall be explained in detail on the sensor website.

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