How to Correctly Select a Rf Admittance Capacitance Level Switch

Since actual operating conditions vary, whether a radio frequency (RF) admittance level switch is selected correctly directly affects how well it matches the site conditions and the accuracy of the measurement. When purchasing an RF admittance level switch, users generally need to pay attention to the following aspects:

1.Understand the properties of the measuring medium
Select an appropriate RF admittance level switch based on the different properties of the medium:
   1) RF admittance level switches can only be used to measure materials with a dielectric constant of ≥1.6. Therefore, the measured medium must have a certain dielectric constant.
   2) Since RF admittance level switches are contact-type measuring instruments, the measured material should not be too large, as this could bend or damage the probe. Therefore, they are not suitable for media with high density and large particles.
   3) When measuring non-conductive media, probes with insulation layers should be selected as much as possible to prevent corrosion from corrosive substances mixed in the medium. For insulated probes, the effects of medium temperature and pressure must also be considered. Temperature and pressure have corresponding curve ranges; operation outside these ranges may damage the insulation layer, allowing the medium to penetrate to the探杆 and crystallize, affecting the measurement results. In addition, for non-conductive medium containers with large diameters, probes with auxiliary electrodes can be selected to improve sensitivity and accuracy, or the RF admittance level switch can be installed as close to the edge of the container as possible.
   4) If the material viscosity is high, the flow rate between the probe rod and the grounded reference electrode will be restricted, so the material level in the pipe cannot truly represent the actual material level in the tank. Therefore, extra caution is needed when selecting an RF admittance level switch.
2.Insertion depth and guard electrode length
RF admittance level switches are point-contact measuring instruments. Once the installation position is determined, the insertion depth and guard electrode length should be selected according to the tank conditions. Insertion depth is key to accurate measurement; generally, the probe should be able to fully contact the material. The length of insertion also depends on whether the instrument will be affected by or damaged due to material impact.

In harsh operating environments, such as when used in hoppers of power plant ash-handling systems, RF admittance capacitive level switches equipped with stainless-steel protective sleeves should be selected to minimize probe damage from material impact. The guard electrode of such instruments generally needs to extend at least 50 mm into the silo.
The guard-electrode lengths of Nuoying NYSP protective RF admittance capacitive switches are typically 300 mm and 590 mm. Custom lengths can also be provided to meet specific site requirements.
3. Process Temperature and Pressure
Operating conditions vary, so the instrument’s temperature rating must match the process temperature.
1) Due to probe-material limitations, temperatures above 260°C require an ultra-high-temperature model. Nuoying’s ultra-high-temperature RF admittance capacitive switch can withstand up to 400°C, making it suitable for most industrial environments.
2) Probe construction generally limits the pressure rating to within 2 MPa. Therefore, these switches are usually applied under atmospheric or low-pressure conditions.
4. Process Connection
Common process-connection types include threaded, flanged, and clamp connections. Selection and customization should be based on the required dimensions, thickness, and material for the tank or pipe.
5. Ingress Protection
In dusty or highly humid environments, an instrument with a high Ingress Protection (IP) rating should be selected. Poor sealing could otherwise affect performance and service life. Nuoying RF admittance capacitive switches feature an IP68 protection rating, providing high sealing performance for dusty and highly humid applications.