A magnetic float level switch is a device used to detect the level of liquid within a tank or vessel. It operates using a float containing a magnet that moves with the liquid level and activates a reed switch or other magnetic sensor to trigger an electrical signal.
The float rises or falls with the liquid level. Inside the float is a magnet that influences a reed switch or sensor located in a fixed position. When the magnet comes close to the switch, it changes state (open or closed), sending a signal to a control system or alarm.
Magnetic float level switches can monitor a wide range of liquids, including:
– Water
– Oils
– Fuels
– Chemicals (depending on compatibility)
– Coolants
Always check material compatibility with the liquid being measured.
– Simple and reliable operation
– No external power required for basic models
– Suitable for high and low-level detection
– Can be used in high-pressure and high-temperature environments
– Minimal maintenance
No, magnetic float level switches are typically used for point level detection (e.g., high or low level alarms). For continuous level measurement, consider using magnetic level gauges or other technologies like radar or ultrasonic sensors.
Common mounting options include:
– Top-mounted
– Side-mounted
– Threaded or flanged connections
Mounting depends on tank design and application requirements.
Materials vary based on application and liquid compatibility:
– Stainless steel (for corrosive or hygienic environments)
– Plastic (for cost-effective or non-corrosive applications)
– Brass or other alloys
-PTFE Coated Stainless Steel
While not designed for precise measurement, they are highly accurate for point level detection, typically within a few millimeters depending on design.
Minimal maintenance is needed. Periodic inspection for buildup, corrosion, or mechanical wear is recommended, especially in dirty or viscous liquids.
(J) – Iron vs Constantan (Most Common)
May be used in vacuum, oxidizing, reducing, and inert atmospheres. Heavier gauge wire is recommended for long-term life above 1000°F since the iron element oxidizes rapidly at these temperatures.
(T) – Copper vs Constantan (Most Common Cold)
May be used in vacuum, oxidizing, reducing, and inert atmospheres. It is resistant to corrosion in most atmospheres. High stability at sub-zero temperatures and its limits of error are guaranteed at cryogenic temperatures.
(K) – Chromel vs Alumel (Most Common Real Hot)
Recommended for continuous use in oxidizing or inert atmospheres up to 2300°F (1260°C), especially above 1000°F. Cycling above and below 1800°F (1000°C) is not recommended due to EMF alteration from hysteresis effects. Should not be used in sulfurous or alternating reducing and oxidizing atmospheres unless protected with protection tubes. Fairly reliable and accurate at high temperatures.
(E) – Chromel vs Constantan
May be used in oxidizing or inert atmospheres, but not recommended for alternating oxidizing or inert atmospheres. Not subject to corrosion under most atmospheric conditions. Has the highest EMF produced per degree of any standard thermocouple and must be protected from sulfurous atmospheres.
(S,R) – Platinum vs Platinum Rhodium (Most Common Real, Real Hot)
Recommended for use in oxidizing or inert atmospheres. Reducing atmospheres may cause excessive grain growth and drifts in calibration.
(N) – Nicrosil vs Nisil (New… Better Than “K”)
May be used in oxidizing, dry reducing, or inert atmospheres. Must be protected in sulfurous atmospheres. Very reliable and accurate at high temperatures. Can replace Type K thermocouples in many application.
| Characteristic | Thermocouple (T/C) | Resistance Temperature Detector (RTD) |
|---|---|---|
| Measurement Range | −250°C to +2600°C | −70°C to +400°C |
| Output Signal | Voltage with respect to difference in end-to-end temperature | Resistance change with respect to actual temperature |
| Accuracy | Less accurate, 2 to 4°C typical | More accurate, up to 1°C typical |
| Stability | Fair, limited to shorter periods | Good, stable over long periods |
| Sensitivity | Lower | Higher |
| Linearity | Poor | Good |
| Extension Cable | High effect, must match T/C type and is more expensive | Lower effect, can use different material, but ultimately limited by lead wire resistance |
| Response Time | Fast (≤ 0.1 s typical) | Slower (1 to 7 s typical) |
| Repeatability | Reasonable | Better & greater standardization |
| Signal Strength | Low, prone to EMI | Higher, more EMI resistant |
| Vibration/Shock Resistance | Good resistance | Less resistant than T/C |
| Sensor Dimensions | Very small to very large | Small to medium |
| Measurement Area | Small, single point-of-contact | Larger, whole element must contact, 1" typical |
| Reference Junction | Usually requires a stable ambient at cold junction | Not required |
| Excitation Required | Not required, self-powered | Yes, reference voltage or current source |
| Cost | Less expensive | More expensive |
| Noise Immunity | Lower noise immunity | Better noise immunity than a T/C |