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REED Resistance PCB Assembly
Principle of Operation :
Level transmitter works on the principle of reed resistance/permanent magnet basis. Reed switches
function like the center arm (as shown in fig. 1) of a potentiometer. As per liquid level float moves up or down, magnet inside the float operates the reed switches thereby causing a change in resistance value. Change in the resistance is measured by the electronics unit and conditioned as a current output of 4 to 20 mA. Signal conditioner is head mounted and of 2-wire loop powered suitable for 12 to 24 VDC giving output of 4 to 20 mA.
Technical Specification : Our Standard Product
Model (VMT-04-F65-AW) , (VMT-04-F92-AW) top mounted magnetic reed/resistance cascade type loop powered 2 wire level transmitter. Process Connection flange 78 or 120 mm diameter with 4 bolt holes of 6mm or 14 mm dia on 65 or 92 mm PCD respectively. Wetted parts flange & float stopper in SS 304. Float material SS 316L and diameter 41, 53 or 68 mm. Operating pressure 10kg/sq.cm and Temperature 125 deg.C. Maximum.
Salient Features :
- Reed switches are hermetically sealed-in glass under an inert gas and therefore protected from contamination.
- Reed switches used by us are suitable for maximum working voltage of 150 VDC and current 1 Ampere.But in our circuitry they are subjected to maximum of 3 VDC and current 1 mA in case of resistance output and maximum of 24 VDC and 20 mA when used in conjunction with a signal conditioner for current output. This ensures long life of the product.
- Reed switches are UL approved and ISO certified for quality management.
- Operating temperature range of reed switches are -40 deg. C. to 125 deg. C.
- Reed Switches are enclosed in a moulded glass filled nylon capsule and therefore protected from mechanical shocks or damage. Moreover the stainless steel float-guide pipe, containing the PCB of reed switches and resistances, is solidly filled with MgO Powder. Hence this is suitable for sub zero temperatures.
- Reed switches are protected against mechanical damage and contact corrosion & vibration.
- Since an outer protection tube is provided (for applications like LPG, where external cage is not possible) the reedswitch sensor assembly can be replaced without disturbing the process.
- Since the float is of 200mm dia with specific gravity -0.4 (for LPG) it will have higher buoyant force. For standard applications float shall be of 48 mm Or 68 mm in diameter.
- Above all float is the only moving part. No wear and tear.
- Applicable in environment with high temp., high pressure, strong acid, strong alkaline an hazardous locations.
- Multiple applications for textile dyeing, sewage water processing, power generating, boiler and petrochemical industries.
- Specific Gravity : Suitable down to 0.7 (upto 0.5 optional)
- Range : 0-150 mm upto 0-3000 mm.
- Resolution : Better then ± 10 mm
- Span suppression : Max 25 % span
- Zero Elevation : Max 25 % span
- Excitation voltage : 12-36 V DC
- Loop Resistance : Max 600 OHMs.