I'm using Modscan to check the data from my Integra 1630 Energy meter.
Often, i will only receive a register value of 0x00 while occasionally a
good reply. I tried changing the scan rate from 100ms to 5s but nothing
changes. The wire connected from my RS485 to the energy meter is less
than 50m.
Anyone has any idea why this is happening and is there any adjustment i
can do to make the slave send back good reply instead of 0x00?

Here are some readings of the replied data from my Modscan ( Hex register )
1st reply - 00
2nd reply - 00
3rd reply - 01 04 04 4c 72 b5 ca bb c8
4th reply - 00
5th reply - 00
6th reply - 00
7th reply - 00
8th reply - 01 44 44 4c 72 b5 ca bb c8
9th reply - 00
10th reply - 00

 

Hi,
Are you using MODSCAN32 software....?
There are two options 1) Modbus-RTU 2) Modbus-ASCII.

So, first of all make ensure that you are using correct protocol which your energy meter is supporting.
2nd also make ensure you have configured proper communication parameter @ both end. Means @ your device on which you are running modscan software & @ your energy meter. Ensure Buadrate, Stopbit, Startbit & parity value.
3rd, may be your converter is faulty or due to impedance matching problem sometime it is not behaving well so make ensure converter is doing well function or not.
If you have written code for energy meter then, just check only communication code so that you will get idea about bug. Just, throw fixed data on hyper terminal continuously. If you are getting all correct data then there is no problem in converter as well as you have configured UART/USART module correctly.

So, let me know, r u simply testing already working energy meter or you have just developed code for it....?
If you are using already working meter then just change converter & see response.

 

Just making a wild guess.
Can you add some resistors to the RS485 bus and make it fail-safe, that is bias it? The zeros indicate that if there is no driver on the bus, it is being sensed as zero, which is a start bit, .... So you get those zeros.