Frequently Asked Questions

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Digital Panel Meters

Determine what you want the panel meter to display for you. Know your input power requirements. Know what signal you are trying to display on the meter and if you require output voltage from the meter or relay contacts to aid in your application. Click here to view additional information on available panel meter selections. If you are having difficulty determining the best panel meter, please fill out our Application Submittal here – this will give us some preliminary information to work with before you contact us.

A panel meter is used to display relevant information about the system being monitored. Having the right digital panel meter can provide an effective tool for sensing and viewing critical process and tank levels.

The desired digital panel meter should be field programmable to display as percent, inches, gallons or other customizable values. In addition, the viewable LED panel meter display should be easy to read from a distance.

Float-Type Sensors

If you are having difficulty determining the best float-type sensor for your application, please fill out our Application Submittal here – this will give us some preliminary information to work with before you contact us.

In most applications, a relay is required to isolate the float switch from the device. The float switch will be connected in series with a relay input coil that typically draws less than 500 mA. When the switch is closed, the relay coil is activated and closes the output contacts. These contacts turn on or off the high current required by the device.

Madison can provide solutions to control the liquid level between a high and a low point. By combining a controller with two float level switch points, a pump or valve can be switched on/off automatically. Two single point float switches, or a custom multi-level float switch with the levels set an appropriate distance apart in the tank can be utilized for this application.

A Double Pole Double Throw (DPDT) relay can be combined with two level switches as shown below for "pump-up" or "pump-down" applications.

Madison stocks an R2-120 Vac pump controller that can be used with float switches or conductivity probes. Madison also 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.

The "Normal" position refers to a float switch in an empty tank, before liquid has affected the float. Each style switch is equipped with a means to identify which type of operation to which the float switch is set.

Vertical: the float's witness mark (stainless steel models) or magnets (plastic models) indicate the NO/NC operation

  • 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: the direction of the arrow on the hex indicates the NO/NC operation

  • NO is indicated by arrow up
  • NC is indicated by arrow down

Use an ohmmeter or continuity meter to verify the switch setting and operation. For vertical switches, 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.

Most stock Madison float switches ship in the Normally Closed (NC) position, unless otherwise specified. To change the contact operation for vertical switches, remove the retaining clip and float, and reverse the float on the stem. The only exception to this is the operation of the subminiature switch (M3326/M3326-NO), which must be specified when ordered, since the float is not reversible on this model. For horizontal switches, simply rotate the switch 180° in the tank installation.

Stock Float switches are accurate to within 1/8” of the center of the float travel, with a hysteresis of 1/16”.

Each individual switch will switch repeatably within 1/32”

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.

Full-Size Floats Miniature Floats Side-Mounted Floats
Stainless steel — 0.55 SG, & 0.70 SG Stainless steel — 0.70 SG M5900 — 0.60 SG
Polypropylene — 0.75 SG Polypropylene — 0.80 SG Polypropylene — 0.60 SG
Buna-N — 0.45 SG Buna-N — 0.45 SG PBT — 0.75 SG
Kynar — 0.75 SG Kynar — 0.85 SG Kynar — 0.75 SG
  • 316 Stainless Steel: For high-temperature (to 250°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.

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.

Click here for details on Madison's approvals.

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 Product Specification Worksheet for easy configuration and ordering.

Yes, as long as the proper wiring is in place as shown below:

Non-Contact Sensors


  • Non-contact – never touches the fluid, ideal for thick, sticky, & semi solid medias, or liquids that should not be touched, as in food processing and acid tanks.
  • Good for waters, oils, chemicals or foods used in industrial, pharmaceutical and food processing applications where non-contact is preferred
  • Good choice for flood monitoring and lift stations, including open channel flow applications
  • Detect liquids or solids through air, or in vented tanks from 4in. to 33ft. depending on model’s range
  • Smaller size and lower cost, ideal for larger tanks, indoor wells, or outdoor ponds

No, ultrasonic sensors will not provide accurate or in some cases, any readings when there are dusts or foams. They can be used with solids, like sands, where the particles settle quickly. They should not be used to measure grains, flour, or materials that produce suspended particles which will interrupt the signal as it travels through air. Radar is recommended for these types of dusty, vaporous, and pressurized applications.

Yes, our standard sensor housings are made of polypropylene or PVC, which are good materials in most food and water applications. We can even offer sensor models with stainless steel sanitary fittings for processing and even PTFE (Teflon) for higher temperature applications upon request.

If the tank vent becomes blocked, pressure can build in the tank. The ultrasonic sensor fitting seal may fail to hold back the increasing pressure if this pressure exceeds the maximum pressure rating.

Yes, but they should be mounted away from the center, where reflected signals concentrate. The sensor should be installed at least 1’–1.5’ ft. from the vertical tank wall or center of the tank.

Yes, but use a protective cover to shield the sensor from weather and direct sunlight is required to protect the sensor from overheating in the sun, or gathering condensation as it heats and cools with large temperature changes.

Yes, but the sensor should be mounted away from the direct material path, or a Down Tube with a venting hole should be used to smooth the reading.


  • Ideal for large tanks or applications up to several hundred feet (specific models only)
  • Good choice for flood monitoring and lift stations, including open channel flow applications
  • Detect chemicals, gases, oils, or hot waters, sees through vapors, steam, foams, and can be adjusted to detect the oil/water interfaces.
  • Accepts 24vDC or 120vAC input power for process tanks and industrial applications
  • Automatically adjust power for environmental conditions or materials
  • Available for explosion proof and sanitary applications.

Ultrasonic and Radar

When compared to other level sensors, ultrasonic or radar level sensors do not contact the material and are not affected by the color, thickness, or composite of the material being measured. These sensors:

  • have varying distance ranges that are field programmable and can detect many types of materials
  • have varying distance ranges that are field programmable and can detect many types of materials
  • provide 4-20mA output and are available with optional RS232, 485 or Hart communication

For more complete information Click Here

Even though these sensors are easily programmed via push button, some models are equipped with MODBUS communication which can be connected via a standard USB connection.

The catalog specifications for each sensor lists the thread type for each Madison sensor model.

The standard Madison ultrasonic and radar sensor housings are PVC. Other models are available with aluminum, Teflon and 316 stainless steel materials. The standard radar antenna is PTFE (Teflon®), but models with a stainless steel reflective cone are available for increased signal strength when required.

Pressure Transmitters

If you are having difficulty determining the best pressure transmitter for your application, please fill out our Application Submittal here – this will give us some preliminary information to work with before you contact us.

0 – 2.5 PSIG to 0 – 150 PSIG, and custom models can be configured to read up to 300 PSI. Stock models are designed for tanks and other low pressure applciations to read continuous fluid levels typically 0 to 5 PSI range (0 to 11.5ft water tanks / well water levels) Ses our stock PH4201-005-P025 model.

PSI (pounds per square inch)
Inches of H2O (1" H2O = 0.0361 PSI. Also, 1.0 PSI = 27.68" of H2O)

Standard models come with CE approvals, but others can be manufactured with FM agency approvals for hazordous locactions and applications.

Long-term stability is normally associated with the change in zero offset due to aging of component and relaxation of the metallic diaphragm over a period of time. It normally causes the zero reading to go high or low over time. Independent tests carried out on these products have shown this number to be 25% under the influence of temperature and pressure cycling for 1500 hours.