RF Admittance type Level Switches

Our RF level switch is widely applied in various products such as Building industry materials, cement, sand, lime, milk powder, flour, salt, food grains, powder, granular, chemical and mining etc. These comprise of a specially designed electronics and sensing probe using Driven Shield Coat Guard circuit and corresponding 3-Element Probe.

The electro-mechanical combination of the Coat Guard technique is there makes the system immune to the material build-up on the probe and material bridging between the probe and the hopper wall. The measured signal does not flow to the hopper wall through the probe in the backward direction but flows only through the material.

The salient features of this level measuring instrument are as follow:

• Three Element Coat Guard Technology
• Can be configured either for High or Low Level point switching
• Reduces the Inventory cost
• Ignores material build-up on the probe
• Suitable for the highly dusty environment
• High Reliability
• Fast and Easy Installation Simple Calibration
• Field selectable operation logic
• Provides economical solutions
• Various models not required 

The specifications of these point level switch are as follow:
 
Switching Unit:

• Housing: Aluminum, weather proof, powder coated. Integral with The probe/ suitable for back panel mounting
• Cable entry: 2 nos.
• Ambient temperature: 0 ° C to +60° C
• Power consumption: 1.9 VA
• Mains Voltage: 230/110 V AC (+/-15%), 50 Hz OR 24 V DC
• Output: 2 sets of potential free c/o contacts rated at 5 amps, 230 V AC for non-inductive loads
• Switching delay: Continuously adjustable From 1 to 20 sec. probe Free or probe covered (Optional)
• Safety operation: Field selected switch over for min. or max. (FSL/FSH) switching points
• Switch status display: Green LED shows Normal, Red LED shows alarm, Yellow
• LED shows power on condition 

Coat Guard Sensing Probe:

• Mounting: Screwed 1 ½ BSP (standard) Or Flanged (optional)
• Sense rod: Stainless steel
• Shield: Stainless steel
• Insulation: PTFE (standard) other on request and as per application.
• Operating Temp in: 100 deg for the integral switching vessel unit.225°C for remote switching unit  

The Principle of Working:

The major shortcoming of the conventional method is that after the level has once increased and then decreased, there may be a coating left on the probe sensed by the instrument as though the level is still on the probe. In our switch, a coat guard amplifier is incorporated in the circuit having its output exactly at the same voltage and phase at all times as its input.

The output is connected through the shield of the low capacitance co-axial cable to the concentric tube on the sense probe, called shield element. There is no current flow through the cable as both the elements, sense and shield are exactly at the same potential and phase at all times.

This results in no change in calibration due to coating on the probe and the temperature effect of the cable. This makes it possible to increase or shorten the cable connecting the switching unit without changing the original calibration.