The VLS series is a piezoelectric driven vibration type level switch that detects the level in bins, silos and hoppers, filled with grained or powdered materials (bulk solids). The instrument can be used for overfill protection, for high or low level alarm.
The blade of the probe vibrate on its resonance frequency. When filling material covers the blade of the probe, the vibration stops. This is sensed by the electronic circuitry and the output relay switches. When the blade gets uncovered, the vibration will restart and the relay will switch back. As only the tip of the vibrating blade is sensitive and not the base, build-up on the container wall has no influence on the function of the instrument. The shape of the blade and its vibration have a self-cleaning effect.
The vibration technique of the VLS offers many unique advantages over alternative level sensing technologies:
• No - Moving parts, maintenance required and calibration required.
• Unaffected by - Environmental changes (e.g. temperature, pressure, humidity), material changes, dust clouds and agitation.
• Maximum - Versatility.
• Design - Single Prong - The single prong design with its sharp edged vibrating blade prevents material build-up typically associated with the dual prong “tuning fork“ design. The
VLS can be used for light material with densities as low as to 10 g/liter. Strong stainless steel construction makes the VLS tough for the use with heavy materials such as
• Fail-safe - The electronic circuit of the VLS indicates power failure. If power supply fails the relay drops into alarm condition.
VLS designed for the detection of all kind of dry bulk solids, powered grain or granular state.
The following list shows some of the materials the VLS has been successfully used for:
a. Powdered milk f. Granular plastics
b. Tea (leaf) g. Frozen chips
c. Wood shavings h. Salt
d. Coffee beans i. Chalk
- Powder coated die-cast aluminum
- Protection IP 66 and IP 67
- 1 cable entry (option: second cable gland)
• Power Supply: Wide range power supply: 20 ... 250V AC/DC
• Power consumption: 3VA
- 2 potential-free change-over contacts (DPDT)
- Max. switching datas AC: 250V-AC, 8A, 2000VA, cosΦ = 1
- Max. switching datas DC: 8,0A at 24V-DC / 1,5A at 48V-AC
- Min. switching datas DC: 24V / 100mA
• Time Delay:
- 1 second from stop of vibration
- 2 to 5 seconds for start of vibration
• Probe Material: Stainless steel 1.4301 / AISI 304
• Process Connection:
- VLS100:1” NPTM
- VLS200/300/400: 11/2” NPTM
- Optional : Screw on flange accordingly to DIN, ANSI or JIS
• Max. Load: Max. vertical and horizontal load upon the end of the blade:
- VLS100: 80N
- VLS200/300/400: 100N
- Max. tensile load of cable VLS400 : 200 kg
• LED Indication (On VLS200, 300 & 400):
- Relay On: Red LED continuous blinking
- Power On: Red LED
• Min. density of material:
- VLS100: 50g/liter
- VLS200/300/400: 20g/liter
• Max. pressure inside bin: 10 bar
• Ambient temperature electronics: -40°C ... + 60°C
• Process Temperature (Probe): -40°C ... + 80°C