User Tools

Site Tools


Mains Frequency measurement with the Janitza UMG96 RM

– Pictures will be taken in the near future –


The Janitza UMG96 is a powerfull device to measure 3-phase Mains supplys. There are several variants of UMG96, with different precision and interfaces to get the values out of the device. I usually use the Modbus/RS485 interface. Janitzas are designed to measure small grids like generators or large distribution boards. So the real-time precision is not that great. I own several of them, that are mostly used in my spare-time-hobby as an Light technican on partys and events. Its always good to know what your current setup is drawing out of a single 3-phase 32A plug…


My actual setup is actually only single phase because there is no three-phase power in the house where i live. I fitted the UMG96RM-CBM in the smallest Spelsberg-Box i could get an added 4mm Plugs for Current an Voltage Inputs. This device is also designed to stay mobile for short-term power measurement.


The measurements are polled with a simple and ugly python script that calls the UMG over Modbus on address 800 (Mains frequency), converts the given binary values to an IEEE754 number and creates a json-object that is send out to the MQTT broker. It runs on an RaspberryPI4. The Modbus-Connection is easily done with an 1$ USB↔RS485 Converter from ebay. Some day I should clean the code up and publish it somewhere.

devicems.txt · Last modified: 2021/09/30 21:49 by matthiass