Carlos Gavazzi Power Meter Communication (WM14-96)

Hi!
I am having a hard time in acquiring the correct data from Carlo Gavazzi power meter model: WM14-96 with RS-485 connection. The modbus serial (RS-485) was converter to modbus ethernet using moxa gateway device, "model: MB3170".

Communication is already established using kepserver software (Modbus Ethernet as device driver is used).Modbus addresses based on WM14-96 manual mapped to kepserver are all good, but the data read is differ from the actual value displayed on WM14-96. See below example..

(ex.. VALUE DISPLAYED for Voltage_L1-L2 = 13.5 kV ;
VALUE READ from Modbus Address (40292) = 63222 (data format-WORD)

anyone can help ????

Thank you...

If the 13.5kV is yor expected voltage and the 63222 is the raw 16 bit data maybe you need to scale the raw value

My calculation gives me 14,000V = 65535 (the max value for 16 bits)

If this is of no help then what voltage did you expect to be displayed
Where or on what was it to be displayed
Give us more details so we can help you

The basic communications manual says,

All the variables, except for the PF values, are represented as signed two's complement integers, by using the number of bytes specified in the memory mapping table.

For the correct interpretation, it is necessary to consider also the decimal point and the engineering unit, according to the following table, and multiply the value by the relevant CT (current transformer) and VT (voltage transformer) ratios:
---------------------------

A table indicates that this particular value has no decimal point.

I'm confused because 63222 is F6F6(hex) or 1111 0110 1111 0110 with the leading bit as a zero.

In 2's complement notation, a leading 1 represents a negative value, a leading zero represents a positive value.

If I convert F6F6 from 2's complement, I invert all the bits and add one.
1111 0110 1111 0110 inverted is
0000 1001 0000 1001
Adding one gets

0000 1001 0000 1010 or 090A(h) or
-2314 decimal.

The voltage transformer ratio needs to taken into account.

With a 6:1 ratio, could the voltage be
13,884V (2314*6), ignoring the negative sign?

hmm I went browsing since i have never used this meter before and cant seem to find that model that reads that high of voltage max i could find was up to 800V.

no clue if this is a scaled out if it was and 65535 being max raw and if say max scaled was 14000V then 63222 would end up roughly 13505V

Is it possibly spitting out a real? if so would require 2 words.

Are the next 2 words or locations where L2-L3 and L1-L3 about the same value or completely something different?

Not familiar with this device at all, so im just guessing as much as you are currently.

If I remember correctly the LAST time I used a Carlo Gavazzi meter it was a little/big endian issue. I think I had to swap words and bites to get the numbers right. It was a long time ago. That was into an Omron PLC. Do not know if they have changed or not.

Tim_Turner said:

Is it possibly spitting out a real? if so would require 2 words.

Click to expand...

Most likely it is 32bit float.

for example:
0x4157F6F6 = 13.497793

kepware format?

The voltage to L1 to L2 is a 2 byte value at 0292h:




Type VC means no decimal point:



An example from the basic comm manual, page 11,
http://www.carlogavazzisales.com/usermanuals.htm
shows a read of the address 0292h and its interpretation as a simple integer:


A value of 13500 volts should appear as something close to 34BCh (unless even lower because of a VT ratio) and your value F6F6 is way off from that value.

I don't understand why they skip from 0292 to 0294 to 0296 for addressing, which is typical of 32 bit values like long integers or 32 bit floating point.

I wonder whether you are actually reading the 0291 or 0293 address, which is some garbage value, due to the dreaded one offset in Modbus.

Do any other addresses read correctly?

If I were doing this, I would read 0292 through 0297 (6 bytes) and see which bytes make sense.

Don't ask me to explain it but when you read 63200 from post 1, as binary you get
11110110 11110110
The first 8 bit images the second 8 bits as 246, 246
11110110

Sirs,

Thanks! I think I got it..
The reason why I was not able to get the right value last time was due to wrong address mapping and different CT & VT value. The addresses shown on the WM14-96 manuals were physical address and not the modbus address. I have to convert the physical address from hex to decimal in order to get the correct modbus address.
For the CT and VT ratio, I was able to confirm the correct settings to the one who configure the said meter.
CT = 1200:5 & VT = 120:1

For "V L1-L2" parameter ==> the address 0292h(hex) is converter to 658(dec) and mapped as 300658 - modbus address

Addressing mapping: (raw value*VT ratio = meter reading)
300658 = 111 (111*120 = 13320) ; actual value displayed on the meter = 13.3 kV

Right now I am having a problem in polling of data... Once I poll 3 parameters the value of the 3rd address I mapped changed (different from the value I poll the data alone) If more than 3 parameters, some or all the addresses mapped to Kepserver becomes bad signal.

test#1 "2 modbus address"
Vab(300658) = 114
Vbc(300660) = 111

Test#2 "3 modbus address"
Vab(300658) = 114
Vbc(300660) = 111
Vca(300662) = 2611 --> INCORRECT VALUE

Test#3 "1 modbus address...Mapped the 3rd address to verify expected value"
Vca(300662) = 111 --> CORRECT VALUE


I already tried to communicate directly on the device using Modbus Serial as the device driver on Kepware..I also tried to use 2 wire and 4 wire connection of RS485, but the same thing happen.


Does anyone encountered this scenario to this particular device and/or other modbus device/s??
I'm wondering if the problem is on the device (WM14-96)...
What could be the possible reason for this??

Thank you Sirs!