A mercury tilt switch opens or closes a contact as its orientation changes. Explore its qualitative cross-section and translate the manufacturer-specified make and break angles into a consistent installation reference.
Tilt-Switch Threshold Calculator
Enter manufacturer-declared make angle, differential angle, installation offset and applied tilt. The worksheet shifts both declared thresholds into the installation reference; it does not predict contact ratings or internal fluid behavior.
Equation Used
- All angles share one declared reference and positive direction.
- Make occurs while tilt increases; break occurs while it decreases.
- Quasi-static comparison only; acceleration, vibration, contact wetting and fluid dynamics are excluded.
- Electrical ratings and legal suitability must come from the exact product data sheet and applicable rules.
The mounting offset shifts both specified thresholds by the same angle. Between make and break, contact state depends on the direction of approach and the previous state; the differential remains a product-specific input.
Sealed liquid contact and gravity
A mercury tilt switch encloses mercury and electrodes in a sealed envelope. Orientation determines whether mercury bridges the electrodes. Product data sheets define the relevant make, break or differential angles relative to a specified mounting reference.
The animation is a qualitative cross-section driven by the entered thresholds. It does not infer a trip angle from vial length, radius or fill.
Legacy component identification
Mercury switches remain in some older thermostats and equipment. Use the worksheet only to translate declared data-sheet angles into an installation reference. It does not establish electrical suitability, replacement equivalence, regulatory status or disposal method for a particular device.
Mounting-reference angle conversion
The model assumes increasing tilt makes the contact. A real part can use a different contact form, orientation or sign convention; follow its own drawing.
Declared-threshold example
With a 10 degree make angle, 5 degree differential and +2 degree installation offset, the installed make threshold is 12 degrees and break threshold is 7 degrees. At 14 degrees the applied tilt is 2 degrees above make.
Product-specific thresholds and ratings
Make angle, differential, contact form and electrical ratings are product-specific. The entered thresholds must come from the exact device documentation; tube dimensions alone do not establish them.
EPA guidance treats mercury-containing thermostats and certain switches as mercury-containing equipment requiring appropriate collection or recycling; intact devices should be handled under applicable local guidance.
Mercury-switch threshold questions
Does the calculator predict the vial's trip angle?
No. Make and differential angles are declared inputs from a data sheet.
What does within differential mean?
The applied angle lies between declared make and break thresholds, so state depends on approach direction and prior state.
Does this page provide wiring or disposal instructions?
No. Use the exact product documentation and local mercury-waste guidance.
Manufacturer and environmental references
- George Risk Industries 4561 data sheet: orientation diagram, On/Off positions, differential angle and product-specific electrical ratings.
- US EPA, Mercury in Consumer Products: mercury thermostats, replacement and collection guidance.
- US EPA, Universal Waste FAQ: mercury switches and mercury-containing equipment classification.
- UK government, Controls on mercury-added products: current controls and limited replacement exemptions.
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