Calculate real sensor value from Modbus

Configuration
,
#1

Hi everyone,

I have installed a water level sensor which provides a 4-20 mA signal.
I am already reading the holding register from a Modbus TCP, succesfully.

#configuration.yaml entry
modbus:
  - name: ZisternenPi
    type: tcp
    host: 192.168.178.63
    port: 502
    sensors:
      - name: Zisterne1
        slave: 1
        address: 1024
        input_type: holding
        data_type: int
        scan_interval: 5
        precision: 2

The value stored in the Modbus holding register is not the actual value (unit) of the measurement.
To get the “mA”-value, the integer value from Modbus holding register hast to be trasformed by calculation (value*20/4095)
I have tried different solutions from various forums, but didnt manage to implement the calculation.
I assume that it is just one line of appropriate code, but i am obvisouly to nooby.
Maybe someone can help me with this?

Dont hesitate to ask if something’s unclear.

kind regards,
Jonas

#2

Hi Jonas,
did you solve your problem?
I have the same issue at the moment and before starting a new thread I wanted to ask if you did your correction factor calculated correctly in the mean time.

I also only need to apply a static factor (raw_value / 5 * 3)
This are my first steps in HA…

Thanks and best,
Matthias

#3

If somebody is interested how to read and calculate values, here is my code. This might not be very elegant nor done in a beautiful way. I am working with HA since 4 hours, so I would call myself a newbie.
I wanted to read the Values out of a Janitza UMG96:


# Loads default set of integrations. Do not remove.
default_config:

# Load frontend themes from the themes folder
frontend:
  themes: !include_dir_merge_named themes

# Text to speech
tts:
  - platform: google_translate

automation: !include automations.yaml
script: !include scripts.yaml
scene: !include scenes.yaml

modbus:
  - name: modbus
    type: serial
    baudrate: 38400
    bytesize: 8
    method: rtu
    parity: N
    port: /dev/ttyUSB0
    stopbits: 1
    sensors:
# Voltages
    - name: umg96_sr01_voltage_l1
      slave: 1
      address: 200
      count: 1
      input_type: holding
      precision: 2
      scan_interval: 5
      data_type: int16
      device_class: voltage
      state_class: measurement
    - name: umg96_sr01_voltage_l2
      slave: 1
      address: 201
      count: 1
      input_type: holding
      precision: 0
      scan_interval: 5
      data_type: int16
      device_class: voltage
      state_class: measurement
    - name: umg96_sr01_voltage_l3
      slave: 1
      address: 202
      count: 1
      input_type: holding
      precision: 1
      scan_interval: 5
      data_type: int16
      device_class: voltage
      state_class: measurement
# Actual Power
    - name: umg96_sr01_power_l1
      slave: 1
      address: 209
      count: 1
      input_type: holding
      precision: 1
      scan_interval: 5
      data_type: int16
      device_class: power
      state_class: measurement
    - name: umg96_sr01_power_l2
      slave: 1
      address: 210
      count: 1
      input_type: holding
      precision: 1
      scan_interval: 5
      data_type: int16
      device_class: power
      state_class: measurement
    - name: umg96_sr01_power_l3
      slave: 1
      address: 211
      count: 1
      input_type: holding
      precision: 1
      scan_interval: 5
      data_type: int16
      device_class: power
      state_class: measurement
    - name: umg96_sr01_power_total
      slave: 1
      address: 279
      count: 1
      input_type: holding
      precision: 1
      scan_interval: 5
      data_type: int16
      device_class: power
      state_class: measurement
    - name: umg96_sr01_energy_total
      slave: 1
      address: 422
      count: 2
      input_type: holding
      precision: 0
      scan_interval: 5
      data_type: int32
      device_class: energy
      state_class: total_increasing
      unit_of_measurement: "Wh"
template: 
    - sensor:
        - name: "Serverraum Reihe 1-2 Leistung L1"
          unit_of_measurement: "kW"
          device_class: power
          state: >
            {% set p_l1 = states('sensor.umg96_sr01_power_l1') | float %}
            {{ (p_l1 / 500 * 3) | round(1, default=0)}}
        - name: "Serverraum Reihe 1-2 Leistung L2"
          unit_of_measurement: "kW"
          device_class: power
          state: >
            {% set p_l2 = states('sensor.umg96_sr01_power_l2') | float %}
            {{ (p_l2 / 500 * 3) | round(1, default=0)}}
        - name: "Serverraum Reihe 1-2 Leistung L3"
          unit_of_measurement: "kW"
          device_class: power
          state: >
            {% set p_l3 = states('sensor.umg96_sr01_power_l3') | float %}
            {{ (p_l3 / 500 * 3) | round(1, default=0)}}
        - name: "Serverraum Reihe 1-2 Leistung Summe"
          unit_of_measurement: "kW"
          device_class: power
          state: >
            {% set p_total = states('sensor.umg96_sr01_power_total') | float %}
            {{ (p_total / 50 * 3) | round(1, default=0)}}
        - name: "Serverraum Reihe 1-2 Gesamtbezug"
          unit_of_measurement: "kWh"
          device_class: energy
          state_class: total_increasing
          state: >
            {% set e_total = states('sensor.umg96_sr01_energy_total') | float %}
            {{ (e_total / 50 * 3) | round(1, default=0)}}
#4

Hallo Matthias,
I am also new at HA - I wanted to read values out of Janitza UMG 508.
The conversion between RS485 and ETH is a Waveshare RS485 to ETH converter.

Now I get hundrets of packets each second - they seem to be empty.

Could you help me to connect to the UMG 508 (it´s the same interface like UMG 96.
Setting at Janitza are RS485: Modbus Master/Gateway, adress is 200, Baudrate 9600.

Could you help please with more informations or manuals how to read the data.
Thanks in advance,
nobi