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How to see all tank levels and temp sensor values from MODBUS on Venus GX

I'm looking through the MODBUS register map for the Venus GX and I see only 1 set of register values for tanks and temperature sensors. The tank values are held in registers 3000-3007 and the temp value in 3300-3305.


The Venus has inputs for 3 tanks and 2 temperature probes. I want to see the different values over a MODBUS connection to a computer. Should there not be 3 sets of registers for tanks and 2 for temperature probes?

Venus GX - VGXModbus TCP
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wkirby answered ·

When you look at the register list you can see all of the available parameters or registers for a single "Device Instance" or "Unit ID" You have listed them correctly already.
You need to select the device that you want to read the parameters from, or in MODBUS terms the "Unit ID" there are many Unit ID's to address the various components and devices connected the CCGX.

You can find the "Device Instance" for a device from the "Device List" page -> "Device" -> "Device Instance"
Alternatively on VRM look at your "Device List" page, expand the device and the "Device Instance" is listed there. Temperature Device Instances are usually 23 and 24, tanks 20 - 22 if I remember right.

Example:
Choose "Unit ID" 23 and read holding register 3304 to get the temperature from one sensor.
Choose "Unit ID" 24 and read holding register 3304 to get the temperature from the other sensor.

EDIT: I forgot to mention that the "Device Instance" does not always map directly to the MODBUS "Unit ID". Consult the spreadsheet tab "Unit ID mapping" to tranaslate the "Device Instance" to the "Unit ID"

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