🔍 Key Concepts
• Review how normally open (NO) and normally closed (NC) contacts are drawn in simple limit-switch symbols (contacts touching vs. separated).
• Compare the extra graphic elements (circle, triangle, semicircle) that indicate what sensing element operates the switch: pressure bellows, temperature bulb, float, or flow paddle.
• Relate device F in the upper right (mechanical float level switch) to the matching schematic symbol in the bottom row that uses the float shape.
💭 Think About
• First, identify in the bottom symbols which ones are clearly NO vs. NC without any special sensing element. Use those to decide which side means open or closed.
• Next, look only at the symbols that incorporate a circle (float) and decide which of those shows the contacts in the open position, as drawn at rest.
• Ask yourself: if the liquid level is low and the float is hanging down, would that switch’s contacts be open or closed according to the symbol?
✅ Before You Answer
• Confirm which symbol style in this figure represents NO (contacts not touching) before considering the special shapes.
• From the symbols that include a circle representing the float, determine which one shows the contacts in the same NO orientation as the plain NO contact symbol.
• Verify that you are not confusing symbols that use triangles or semicircles (often pressure, flow, or temperature elements) with the one that specifically indicates a float level element.