I am using looking at ION setup using the Modbus Tester Interface and pulling back the below values for Frequency
3110 - 16967 or 4247 in Hex
3111 - 60918 or EDF6 in Hex
I know that you can use a IEEE 754 converter to convert the Hex to a useful decimal value however i was looking for a formula to do this or another way around,
We come across a lot of problems in Technical Support where customers are using Modscan or other Freeware tools and the figures appear to them to be in correct because they would see 16967 & 60918 instead of 50 Hz so looking for a way of simplifying this
Could anyone comment?
Please describe more detail what you want . I don't understand what you're saying although I read many times your post
Sorry for this
register 3110 on the PM5000 meters is for Frequency in 32 Bit Float
When reading on ION setup you get
3111 - 60918
Is there a way to convert these numbers to display 50 which is what it should read?
For reading Float32 Bit, you can choose it easily as below
But unfortunately, Floating point in PM5000 is Most Significant Register First, but the Modbus Interface Testing in IONSetup doesn't support this display, so, you also can not display 50 Hz .
You can use Modscan or some Software which support this
Finally, I just recommend that Modbus Tester Interface just a tool for testing the Healthy of Communication, not to view real Data of Power Meter
If you would like to view Data, yoiu can choose View/ Data Screen, click on Real time item on the left window to view
Thanks and Best Regards
Thanks for your reply Tri DANG , very helpful
Have you ever heard of having to input the register before the one you are using?
For example 3026 which is L-L Avg Voltage? i have had to input 3025 to get the figure to work
Is this something you have come across before?
The register offset is defined in the Modbus Application Protocol specification (available from www.modbus.org) and states for the Read Holding Register function code (0x03):
6.3 03 (0x03) Read Holding Registers
This function code is used to read the contents of a contiguous block of holding registers in a remote device. The Request PDU specifies the starting register address and the number of registers. In the PDU Registers are addressed starting at zero. Therefore registers numbered 1-16 are addressed as 0-15.
MODBUS Application Protocol Specification V1.1b3 Modbus
April 26, 2012 http://www.modbus.org 15/50
A very simple (and slightly inaccurate) way to do the conversion is to use the following formula (from Wikipedia on single precision):
S = the sign bit (i.e. whether the first register is greater than 32767, then it is negative)
m = the fractional portion
x = the exponent
First take the first register and remove the sign bit (if its > 32767, subtract 32768, otherwise proceed) and then divide by 128. This will give you a decimal number (let's call it x.B where x is the exponent and B is the decimal portion). Next you would take the decimal portion (B) and then multiple by 8388608 and add the value of the second register to obtain the fractional portion.
So given you example of the first register having 16967 and the second 60918, we get:
s = 0 since the first register is not greater than 32767 (thus the value is positive)
next we take the first register and divide by 128 to yield: 16967 / 128 = 132.5546875
thus x = 132
we then take the decimal portion (.5546875) and multiply by 8388608 and get 4653056 and then add the second register to get the fractional portion (m): 4653056 + 60918 = 4713974
Finally putting everything thru the formula yields:
1 x (1 + 4713974 x 2^-23) x 2 ^ (132-127)
which solves to
1 x (1 + 0.561949491) x 2 ^ 5
1 x (1.561949491) x 32 = 49.98238373
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