# Emon Tx Shield Pi serial **URL:** \ **Category:** emonTx\ **Created:** [20 January 2023 21:12 UTC](https://community.openenergymonitor.org/t/emon-tx-shield-pi-serial/22561 "2023-01-20T21:12:36Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![Robert.Wall](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/robert.wall/32/38246_2.png) [@Robert.Wall](https://community.openenergymonitor.org/u/Robert.Wall)\ **Post date:** [20 January 2023 21:54 UTC](https://community.openenergymonitor.org/t/emon-tx-shield-pi-serial/22561/2 "2023-01-20T21:54:28Z")
Welcome, Jim, to the OEM forum. I’ll answer what I can, I need to leave the other points to those who know those areas better. > [@drjim](#): > > 9v AC adaptor from the shop (seems to give 12v). That’s OK - the 9 V output is on full load, the load the Shield provides is “minimal” - almost nothing. Depending on exactly which adapter you have (UK, EU, US) the output voltage is 11.6 V ±3%, 11.6 V ±5% or 12.0 V ±5% respectively at the nominal mains voltage. The voltage calibration constant is the mains voltage that would give 1.0 V **at the ADC input** - this is after the resistive voltage divider on the Shield. The same goes for your c.t. - in this case it’s the current that gives 1.0 V at the ADC input, which in this case is the jack socket. I’m by no means a RPi expert, but my crib notes say “Serial USB connection to Raspberry Pi: The address you need to use in emonhub will be /dev/ttyACM0 (assuming this is the first/only arduino connected) instead of the usual /dev/ttyAMA0” This might help: [Multiple emonTX Serial connections - #2 by borpin](https://community.openenergymonitor.org/t/multiple-emontx-serial-connections/15221/2) --- _[View the full topic](https://community.openenergymonitor.org/t/emon-tx-shield-pi-serial/22561)._