1、 Overview
The FT600 tuning fork level switch is a new type of level switch. The tuning fork is excited by a crystal to produce vibration. When the tuning fork is immersed in liquid material, the vibration frequency changes, which are detected by electronic circuits and output as a switch value.
The tuning fork type liquid level switch, also known as the "electrical float", can be used in situations where a float level switch is used or where a float level switch cannot be used due to scaling, agitation, turbulence, bubbles, vibration, and other reasons. Due to the absence of moving parts, the tuning fork level switch does not require maintenance or adjustment and is an upgraded product of the float level switch. This product is used in the petrochemical, light industry, food, and water treatment industries to provide upper and lower limit alarms and control for liquid levels.
Solid powders with good flowability in hazardous areas such as tap water, mineral water pulp, glue, dyes, wastewater, mud, and acidic and alkaline solutions that can produce gases, such as liquid beer, beer fermentation agents, and beverage diesel.
2、 Technical parameters　

Power supply: 24VDC (standard) 220VAC (optional)
Output mode: SPDT relay (single pole double throw)
● Output capacity: 5A@220VAC / 3A@24VDC
● Environmental temperature: -20 ℃~70 ℃
● Medium temperature: -40 ℃~150 ℃
Work pressure: less than 2MPa
● Medium density: minimum 0.6g/cm3
Fork body material: 316 stainless steel
● Action point: Insert vertically into the water at a distance of 25mm
● Corresponding time:<0.5s
● Delay: 1-50s (optional)
Power consumption: 0.5W
● High and low level alarm: It can be set to HLFS (high level alarm mode) or LLFS (low level alarm mode) on site
Electrical interface: G1/2 "
● Process connection: 1 "NPT thread installation (standard, optional BSPT); Flange installation (optional)
● Shell protection: IP65
Explosion proof: Exd II Ct4
3、 Product Features
Strong adaptability: Different electrical parameters and densities of the tested liquid do not affect the measurement. Scaling, agitation, turbulence, bubbles, vibration, moderate viscosity, high temperature, high pressure and other harsh conditions have no effect on the detection
No need for calibration: As the detection of tuning fork limit switches is not affected by the electrical parameters and density of the measured medium, no on-site calibration is required for any type of liquid being measured
● Maintenance free: As the detection process of the tuning fork limit switch is completed by electronic circuits without moving parts, it does not require maintenance once installed and put into operation

4、 Working principle:
The working principle of the tuning fork level switch is based on whether the material has resistance to the vibrating tuning fork, detects whether the material level has reached or exceeded a certain height, and sends an on/off signal. This principle does not require significant mechanical movement, has low driving power, does not require calibration, and can be quickly and cost effectively started. The mechanical structure is simple, with no mechanical moving parts, no maintenance or wear, long operating life, and is sensitive and reliable.
The tuning fork of the sensor is made of a metal with good elasticity, usually made of stainless steel such as SS316. The metal itself has a determined natural frequency, and if the frequency of the applied alternating force is consistent with its natural frequency, the fork body is in a resonant state. Due to the resistance micro waves of the surrounding air to vibration, the energy loss inside the metal is minimal, so only a small driving power is needed to maintain strong vibration.
The tuning fork of the sensor vibrates at its natural frequency. When the tuning fork touches liquid or other materials, its natural vibration frequency decreases, and energy is consumed in the friction between material particles, forcing the amplitude to rapidly decay and stop vibrating. The frequency number activates the liquid level switch, generating an on/off signal.
In order to provide alternating driving force to the tuning fork, the tuning fork level switch sensor uses an amplification circuit to apply an alternating electric field to the piezoelectric element, and generates mechanical force on the fork body through the inverse piezoelectric effect. Detecting vibration using the positive piezoelectric effect of a set of piezoelectric elements, which converts the vibration force into a weak alternating electrical signal. Then, the signal from the damping element is amplified by an electronic amplifier and a phase shifting circuit, and after phase shifting, it is applied to the driving element to form a closed-loop oscillator.
In this closed loop, there is both mechanical and electrical energy, and the fork is one of the joints. If it is still difficult to vibrate due to material resistance, the amplitude and phase of the positive feedback will change significantly, which will break the oscillation conditions and stop the vibration. As long as appropriate devices are connected to the output terminal of the amplification circuit, it is not difficult to obtain switch signals.
5、 Installation instructions
The tuning fork type level switch is usually installed on the side (on the side of the warehouse wall) to detect the upper and lower limits of the material level height on the side wall of the warehouse; When it is inconvenient to open holes on the side of the warehouse, top mounting (installed at the top of the warehouse) can be used for installation, and the position should be selected to avoid material impact during feeding; It can also be installed on the pipeline to prevent the pump from running out of material.
1- High level detection (top mounted)
2- High level detection (top mounted)
3- High level detection (side mounted)
4- Low level detection (side mounted)

Installation diagram of metal cans

Correct installation, incorrect installation
Attention: When installing on the side, the direction mark must be vertically upward or downward

Installation Diagram for Pipeline Inspection

Correct installation, incorrect installation

Attention: During installation, the direction mark must point in the same direction as the pipeline

6、 Product selection

• FT-600 tuning fork level switch.pdf