Query several Modbus meter by RS485 RTU Part 2

on may I´ve asked about querying modbus meters (Query several Modbus meter by RS485 RTU)

now I've finally implemented it with 3 meters:
SDM.json (85.3 KB)

I just wanted to ask if there is any experience with the most minimal queue delay:

I set it to 5ms. Where is the limit ?

If I connect the query as a loop, I get every second a run.

First I tried without "queue commands" - but so ID2 + ID3 were ignored (not queried).


Hello Becker,

I could be wrong but i dont think the Queue Delay matters so much in your configuration .
Wiring the Modbus Read nodes one after the other (which is correct) - when one finishes its Read it will trigger the next. All good .. so you are controlling the "Delay" yourself.

What matters is finding the "sweet spot" with that initial Inject Node that you have set to 2 seconds.
If the whole read process hasnt finished and you start a new Read .. modbus commands could start queuing up. (You can use the modbus-queue-info node to monitor the queue if that happens)

1 Like

I've had trouble with this in the past and found it to be dependant on the device that was being polled. Some devices share a processor to deliver this info and others are just plain slow. From memory 2-5 ms has worked well for me in the past.

I just checked my current config which is polling a Huawei inverter and it is set to 1ms. I get errors about every 30 seconds or so with no response from the device. I'm not sure if this is related.

Summary: I think it depends on the devices you're polling.

1 Like