TABLE OF CONTENTS

1. What products are involved?

Rheonics SRV viscometer and SRD density-viscosity meter.

2. How do we know if our Rheonics sensor needs calibration?

Rheonics sensors are factory-calibrated and do not require re-calibration in the field. However, periodic verification or re-calibration may be necessary to meet regulatory requirements (e.g., ISO, FDA).

Note: Performing a periodic air check is a simple method to determine if the sensor requires calibration.

3. Rheonics vibrational sensor technology

The SRV and SRD are based on a balanced torsional resonator (BTR), unaffected by external vibrations. Fluid properties sensors based on vibrating resonators fall into two categories: density and viscosity measurement.

More information about the operation principle can be found here Rheonics vibrational sensor technology: demystified

This “air check” is useful for quickly verifying the SRV and SRD calibration and baseline. The sensor does not use moving parts, so if readings in air are zero, there is no way that the factory calibration has been affected, or any long-term drift has occurred. 

4. Quick verification of SRV calibration in air

Figure 1. SME-TRD with SRV probe 

  1. Remove the SRV from the process
  2. Clean the SRV if the probe is dirty
  3. Leave the SRV in the air, and verify that nothing is in contact with the sensing element
  4. Verify the viscosity reading is zero. This can be checked through the SME-TRD display, RCP software, or any external integration system (e.g. PLC).

5. Quick verification of SRD calibration in air


Figure 3. SME-TRD with SRD probe

  1. Remove the SRD from the process
  2. Clean the SRD if the probe is dirty
  3. Leave the SRD in the air, and verify that nothing is in contact with the sensing element
  4. Verify the viscosity and density readings are zero. This can be checked through the SME-TRD display, RCP software, or any external integration system (e.g. PLC).

7. What to do if the air values are non-zero?

If the values are non-zero, the next step is to use the scaling tab to baseline the 0 cP. Deposits on the probe could cause drift, so it’s important to clean the probe. If the value reads zero after cleaning, the issue is resolved. 

If it remains non-zero, the scaling tab can correct the drift. open the RCP software and go to the “Scaling tab” in expert mode.


7.1. This offset can be observed in the “Measurement tab” where viscosity is a non-zero value.


Figure 4. Viscosity reading with offset.


7.2. Using the “Scaling tab” to fix the viscosity offset.


Check this support article for more information: Scaling: How to create correlation between lab and inline measurements?


Figure 5. Scaling tab, setting correct viscosity


7.3. Once properly scaled the viscosity output goes down to zero.


 Figure 6. Scaled viscosity output when non-zero viscosity reading

8. References

1. How to clean your Rheonics probe?

2. Calibration of inline process viscometer SRV in field and factory

3. Calibration for the Type-SR sensors in field, verification and re-calibration