Madison offers several solutions to control fluid levels in custom applications. The most common is by using a Double Pole Double Throw (DPDT) relay combined with a custom two-level float switch or two independent Normally Open float switches placed at the levels to turn the pump on and off.

The diagrams below illustrate typical circuits for these "pump-up" or "pump-down" applications.

For Pump-Up Applications	For Pump-Down Applications

Madison also stocks an R2 pump controller that can be used with float switches or conductivity probes. Madison stocks relays and controllers to activate pumps, solenoid valves, motors and alarms. Our fluid control engineers are on-hand to assist you with these applications.

Each style switch is equipped with a means to identify which type of operation to which the switch is set.

Vertical: NO/NC operation is indicated by the position of the witness mark (stainless steel models) or magnets (plastic models). NO is indicated by circle up (stainless steel) or magnets down plastic); NC is indicated by circle down (stainless steel) or magnets up (plastic).

Horizontal: NO/NC operation is indicated by the direction of the arrow on the hex. NO is indicated by arrow up; NC is indicated by arrow down. An ohmmeter or continuity meter can be used to verify the switch setting and operation. Simply connect the meter to the leads and, with the float hanging down away from the fitting, measure the switch. If the meter reads a short, then the switch is normally closed and will open on rise.

All switches are shipped in the Normally Closed (NC) position, unless otherwise specified. To change the contact operation, simply remove the retaining ring and float and reverse the float on the stem. The only exception to this is the subminiature switch (M3326/M3326-NO), for which operation must be specified when ordered, since the float is not reversible on this switch.

Madison can furnish an Interface Float that, given two mediums, is designed to sink in one medium and float in the other. A typical application would be one where oil and water accumulate in one tank, and sensing of only a fall in water level is required (oil level is not an issue). Since a standard float of any material will float in any liquid with a specific gravity higher than the specific gravity of the float, Madison would “weight” the float to a specific gravity of 0.95. Since the specific gravity of the oil is 0.8-0.9 and that of the water is 1.0, the float will sink in the oil and float in the water. Both full-size Buna-N and polypropylene floats can be modified in this manner.

One of the main considerations when choosing a switch is the specific gravity of the float. To make sure the float will function properly in the application, the specific gravity of the fluid must be greater than the float's specific gravity at the maximum temperature range of the application. For reference, below are specific gravities of some of our floats. See our standard floats page for details.

Full-Size Floats:
Stainless steel — 0.55 SG, except M5600-PR float is 0.70 SG
Polypropylene — 0.75 SG
Buna-N — 0.45 SG
Kynar — 0.75 SG

Miniature Floats:
Stainless steel — 0.70 SG
Polypropylene — 0.80 SG, except M3326 is 0.60 SG
Buna-N — 0.45 SG
Kynar — 0.85 SG

Side-Mounted Floats:
M5900 series (stainless steel) — 0.60 SG
M5970 — 0.70 SG
M5010 — 0.60 SG
M4010 — 0.45 SG
Polypropylene — 0.60 SG
PBT — 0.75 SG
Kynar — 0.75 SG

316 Stainless Steel: For high-temperature (to 300°C), high-pressure (to 300 PSIG) and corrosive conditions. Commonly used in food processing, medical, heating and cooling equipment.

Polypropylene & Polysulfone: For acidic conditions, such as found in electroplating and metal cleaning. Another choice for lower-temperature (to 105°C) food processing applications (Madison Company uses only polypropylene that is FDA-approved for food contact). Also a good choice for general-purpose applications in commercial or consumer appliances and equipment.

Brass & Buna-N, PBT & Buna-N: The selection for petroleum-based liquids, such as lubricating oils, gasoline and diesel fuels. Widely used in storage tanks of vehicles, generators, transmissions and hydraulic systems. Other uses are in lubrication, recovery, refining and fuel processing equipment. PBT is not suitable for use at temperatures above 130°C.

Kynar: Chemical- and solvent-resistant properties make this material a problem solver for many applications. Its high-purity nature is ideal for food handling and sensitive laboratory or test equipment.

Madison products can be ordered direct from the factory. Minimum order is $300. We accept payment by credit card (Visa, MasterCard and American Express) or COD. Please contact Madison to set up an account on open terms.

We also have a network of distributors located in various regions across the U.S. and Europe. Click here for our directory of Sales Representatives.

Turbulence, which can be caused by a vibrating tank, intensive mixer agitation or surging of liquid during tank filling, can result in premature failure of both the switch and the relay, due to chattering. A very low-cost, reliable solution to this problem is the use of a slosh shield. This device is equipped with fluid and vent holes and surrounds the switch float to prevent erratic switch operation.

Madison stocks a complete selection of slosh shields for vertical and horizontal switches in stainless steel, polypropylene, PBT, brass or Kynar.

Madison Company offers a full range of value-added options, including terminations and connectors; extra-long or -short lead lengths; special cable or wire; shrink tubing for wire protection; and special sealing materials, such as Viton or Buna-N gaskets and O-rings. We can also meet special requirements with our temperature sensors, slosh shields and weather-proof or explosion-proof junction boxes.

Our vertical M5600 series and our horizontal M5900 series are rated explosion-proof by UL and CSA for use in Hazardous Locations, Class I, Groups A, B, C, D; Class II, Groups E, F, G; Class I. These switches are also approved by DEMKO for use in potentially explosive atmospheres EEx d IIC T2 and carry the Ex mark.

Yes, standard float switches may be affected by these conditions because such particles can cause a float to stick or to not operate at all. Instead, we recommend using a conductivity switch, such as our multi-point model M3784 or single level model M3850. Because our conductivity switches have no moving parts, operation of these switches is not interrupted. Furthermore, the M3827 side-mounted switch is engineered such that the magnetically actuated reed switch will not come in contact with the fluid being monitored. The float is attached to an extended pivot arm that, when moved, triggers the switch function. This switch is ideal for use in heavy-bodied liquids or in fluids containing metal particles that would otherwise be attracted to a conventional style float.

We have a continuing program to upgrade our list of UL and CSA approvals. Madison Company's liquid level switches have general-purpose approval as recognized components granted by UL under file number E54633 and CSA file number LR56150.

Some Madison switches are also NSF-certified for food applications.

In addition, we are self-certified for CE under the following directives:

EN60730-1 — Automatic Electric Controls for Household and Similar Use - Part 1: General Requirements (1995)

EN60730-2 — Automatic Electric Controls for Household and Similar Use - Part 2: Particular Requirements - Section 2-15: Automatic Electrical Water Level Sensing of the Float or Electrode-Sensor Type used in Boiler Applications (1996)

Low Voltage Directive (72/73/EEC)

Our M5600 and M5900 switches are certified explosion proof by DEMKO

No. 99E.126064X EEx d IIC T2: Protected for use in potentially explosive atmospheres.

Click here for details on Madison's approvals.

Madison Company periodically life tests the reed switches used in its liquid level switches. This is done to ensure that the reed switches, as obtained from our vendors, have not had a shift in operating characteristics. The reed switches are tested, rather than the complete assembly, because they are the principal electrical component of the liquid level switch.

The testing is performed by cycling the switch, using a standard coil, one million times. The load on the switch is an incandescent light bulb rated for the maximum wattage of the reed switch (i.e., a 60-Watt bulb is used to test a reed switch rated at 60 Watts maximum).

A resistive load (light bulb) is used because it provides a uniform standard against which comparisons can be made. Inductive loads vary greatly from device to device, making comparative analysis very difficult.

The degree of deterioration of a reed switch after life cycle testing is measured by determining the changes in contact resistance, pull-in force and drop-out force as compared to those same measurements made before testing commenced.

Madison Company has the capability of doing life-cycle testing of reed switches using specific electrical loads, such as relays or solenoids supplied by our customers. Please contact the factory for more information.

Our sensors are warranted for one year from date of manufacture. We only accept returns that are authorized by the factory. Please contact the Sales Department for a Return Authorization Number.

Yes, we offer a variety of custom packaging – bar coding, special unit packs, etc. Please contact the factory for more information.

In order to better serve our customers, we continually review our Lean Manufacturing techniques and Kanban systems to meet demands. These systems eliminate both overstocks and stockouts and allow us to maintain the proper level of inventory for both standard switches and custom fittings.

Standard switches have a lead time of one to two weeks. Custom switches have a three-week lead time.

Yes, Madison offers multi-point switches in many configurations. Our full-size multi-point switches can be set for up to six levels, and our miniature switches can be set for up to four levels. They can be mounted within any vessel, utilizing male pipe threads, pipe plugs, flanges or bulkhead fittings. The length of each switch, as well as the location of the floats, can be established by the designer. For those users who want to design and install their own systems, multi-point switch kits are available in three different materials. Click here to fill out our multi-level switch specification sheet for easy configuration and ordering (PDF format).