1. Switch your multimeter to the "Diode Test" position.
2. Hold the positive lead to the JFET's gate terminal.
3. Hold the negative lead to the JFET's source terminal. The multimeter should show a p–n junction forward voltage drop ~ 650-750 mV.
4. Hold the negative lead to the JFET's drain terminal. The multimeter should show a p–n junction forward voltage drop ~ 650-750 mV.
5. Hold the positive lead to the JFET's source terminal. The multimeter should show a low voltage drop - the JFET is ON.
6. Hold the negative lead to the JFET's gate terminal. The multimeter should show a p–n junction reverse voltage drop - overrange.
7. Hold the negative lead to the JFET's gate terminal. Connect the JFET's drain terminal to the JFET's gate terminal. The multimeter should show a overrange - the JFET is OFF.
For n-channel JFET
1. Switch your multimeter to the "Diode Test" position.
2. Hold the positive lead to the JFET's gate terminal.
3. Hold the negative lead to the JFET's source terminal.
The multimeter should show a p–n junction forward voltage drop ~ 650-750 mV.
4. Hold the negative lead to the JFET's drain terminal.
The multimeter should show a p–n junction forward voltage drop ~ 650-750 mV.
5. Hold the positive lead to the JFET's source terminal.
The multimeter should show a low voltage drop - the JFET is ON.
6. Hold the negative lead to the JFET's gate terminal.
The multimeter should show a p–n junction reverse voltage drop - overrange.
7. Hold the negative lead to the JFET's gate terminal. Connect the JFET's drain terminal to the JFET's gate terminal.
The multimeter should show a overrange - the JFET is OFF.