To understand the scaling options and coefficients, please refer to this article
In the file table attached you will find the Modbus registers associated with each of the measurement parameters provided by SMET.
To be able to calibrate you will need to work on the holding registers (Modbus Functional command FC3)
Parameter List is as follow:
There are two methods to scale using Modbus registers.
Method 1: The sensor is in the reference fluid.
In this case we are assuming that the sensor is already dipped in the reference fluid.
- Write (any value) to the register identified as Sample 0. This will instruct the SME to take a measurement and store it as that sample.
- Write the reference value, this is, the value expected, in the register Lab 0.
- Write the value 1 (offset calibration) in the register "supported_types". This will make the offset calibration according to the values in Lab 0 and Sample 0.
- To see the calibration results, read the "current coefficients" registers.
- To use the factory or user calibration coefficients as the current ones in use write the values 1 or 2 in the "Select Mode" register. On read, this register returns 0 value.
In this case we need to take two samples, in theory these samples should be taken at different conditions. For example, different temperatures of a calibration fluid.
Method 2: Direct calculation of scaling coefficients
You can use the equations from this article
https://support.rheonics.com/en/support/solutions/articles/81000391533-scaling-sme-parameters to calculate the C0 and C1 coefficients, if you have previous knowledge of the Laboratory and sample values taken by the sensor.
You can write these coefficients in the registers:
C0 = current_coeff and C1 = current_coeff