What is the purpose of this article?
Explain the procedure to add scaling coefficients to Rheonics sensor readings using the RCP Software, to, for example, create correlations.

What products are involved?
Rheonics SRV viscometer, and SRD density and viscosity meter.
Rheonics DVP Density and Viscosity Probe and DVM Density and Viscosity Module.

Scaling is an important tool when performing a calibration and/or correlating two or more values. Most of the time, a process measurement is compared against a known measurement (the standard) When you need to scale the Rheonics sensor measurements to match the standard or reference laboratory value, use the “Scaling” Rheonics Control Panel function.

Before adding any scaling factors to the readings, it is recommended that the user verify the correlation is possible between the Rheonics sensor and the external sensor. This is done by comparing and plotting readings for viscosity and/or density from both instruments and identifying a correct linear proportion. Multiple data points should be evaluated to ensure the scaled values will be valid for all operation ranges and not for a single point.

1.1. Open RCP and go to the “Scaling” tab (This requires to enable expert mode - find password required on RCP Manual). Once there, open the “Select Measurement” drop-down list and select the desired measure to scale.

Figure 1. Select Measurement tab options

1.2. When a parameter is selected, the software is going to automatically populate the unscaled value and scaled values.

Figure 2. Viscosity selected, the unscaled and scaled values are displayed in the screen

1.3. Select the scaling method, “Single Point” for offset calibration should be used when either the measurements range is kept around a narrow value, or when the sensor response and the ideal response maintain the same behavior within the sensor operation range or “Two Point” for offset and slope scaling when the sensor works in a wide range of measurements and the difference between the ideal response and the sensor response changes linearly within that range. 

Figure 3. Scaling methods

2. Single point calibration (Offset) 

2.1. After selecting the “Single Point Scaling”, click in the read button, this will populate the “Sensor Read Out” box with the raw value currently being measured by the sensor. 

Alternatively, the user can write in the box a specific value of viscosity that was previously determined to create a correlation (i.e. the real-time value is not the only input possible). This holds true for both single and two point scaling.

Figure 4. Click-in Sensor Read Out and populate

2.2. Save the read or specified value (Sample 1) by clicking in the button “Set”.

Figure 5. Saving Sample 1 by click-in set button

2.3. Write the “expected value” for the measurement, for the offset calibration this means that the sensor output is higher or lower than the expected reference value. Click “Write” to store the value in SME. 

 Figure 6. Saving lab value 1 of the expected value.

2.4. Click “SCALE” to use the stored samples to scale the SME output. In this example notice that the software automatically shows the value that fix the parameter to the closest value to the desired value.

Figure 7.  SCALE BUTTON to load the stored samples, we noticed the closest value to fix the expected value.

2.5. Read the Scaling Coefficients

3.1. After selecting the “Two Point Scaling”, click in the read button, this will populate the “Sensor Read Out” box with the correct raw value and save these values.

As for the single-point scaling, the user can directly write in the "Read Out" boxes specific values of viscosity that were previously determined to create a correlation and not use the "Read" button (i.e. the real-time value is not the only input possible). 

Then click the “Set” button.

Figure 8. Saving Sample 1 by click-in set button in Two-point Scaling

3.2. Add the expected values and click the “Write" buttons.

Figure 9. Click to save LabValues in Two-point Scaling

3.3. Click "Scale" so the SME calculates the coefficients and outputs the scaled/calibrated value. 

For this example, the scaling will 100x the actual viscosity.

Figure 10. Scaling 100x the current viscosity value.

The two-point calibration allows offset and slope calibration, below find an example with this. In this example, the Scaled value will be 84x the viscosity with an offset of 20.

Figure 11. Scaling of both offset and slope.

Resources:

Theory behind scaling: https://support.rheonics.com/support/solutions/articles/81000391533-scaling-sme-parameters 

To enable expert mode: https://support.rheonics.com/support/solutions/articles/81000289485-set-density-input-to-srv-inline-viscometer-for-dynamic-viscosity-and-kinematic-viscosity-outputs