🔍 Key Concepts

• Compare how a traditional thermostatic expansion valve (TXV) senses superheat versus an electronic expansion valve. • Look closely at which valve has an external electronic sensing device with two probes instead of a single pressure bulb and capillary tube. • Identify where thermistors (temperature-dependent resistors) would physically be installed to sense evaporator outlet temperature and superheat.

💭 Think About

• Which of the four valves clearly uses a mechanical power element (diaphragm and remote bulb) to sense temperature, and which one shows electrical components instead? • On the illustration, which option includes a separate module with two small probes that could be clamped to the suction line to measure temperature? • If a valve uses thermistors, what kind of signal will be sent to the valve (mechanical pressure through a capillary, or electrical signal through wires)?

✅ Before You Answer

• Verify which drawing shows a remote sensing bulb and capillary tube only (that one is NOT using thermistors). • Look for the option that has a separate electrical module with leads/probes that could be strapped to the evaporator or suction line. • Confirm that the chosen valve has no traditional thermostatic bulb but instead appears to be controlled by an electronic sensing and control device.