06/05-W97-Iv/Sel Instruction sheet 555 612

Demonstration triode (555 612)

1 Pin base (for cathode contacting) 2 Getter mirror (for maintaining the vacuum) 3 Grid connection 4 Anode connection 5 Anode 6 Grid 7 Incandescent cathode 8 Cathode plate

Safety notes 1 Description The demonstration triode enables basic experiments to be Danger of implosion: the demonstration triode is a high- carried out relating to thermionic emission of electrons from vacuum tube made of thin-walled glass. hot cathodes (Edison effect), determination of the polarity of - Do not expose the demonstration diode to mechanical the emitted charge carriers, triode characteristics and the ap- stress, and connect it only if it is mounted in the tube plication of the triode as an amplifier. stand. During operation, electrons are emitted from the incandescent - Treat the contact pins in the pin base with care, do not cathode. They form a space charge cloud in front of the cath- bend them, and be careful when inserting them in the ode. If an anode voltage is applied, the electrons are acceler- tube stand. ated towards the anode and a current flows. By variation of the - Treat the anode and the grid connection with care. grid voltage, the space charge cloud and thus the cross current through the tube can be influenced. During operation, hazardous contact voltages may be ap- plied: - Connect the demonstration triode with safety connection 2 Technical data leads only. Heating voltage UF: 0 ... 7.5 V (rec.: 6.3 V)

- Establish connections only while power supplies are Heating current IF: approx. 2.5 A at 6.3 V switched off. Anode voltage UA: -300 ... 300 V -5 ... 5 kV (if the cathode heat- During operation, the demonstration triode is heated by the ing is switched off) cathode heating: Anode current I : approx. 0.2-1 mA at U = - If necessary, allow the demonstration diode to cool A A 300 V/ U = 0-9 V/ U = 6.3 V down before dismounting. G F Grid voltage UG: -10 ... 10 V (in triode operation) The demonstration diode may be destroyed by voltages or -300 ... 300 V (in diode opera- currents that are too high: tion) - Keep to the operating parameters given in the section on -5 ... 5 kV (if the cathode heat- technical data. ing is switched off) Pressure: <10-6 hPa Diameter: 90 mm Total length: 270 mm Mass: 250 g

Instruction sheet 555 612 Page 2/4

3 Putting into operation additionally required: 1 tube stand 555 600 1 DC power supply 521 65 3.1 Mounting in the stand tube: 3.2 Connection to the DC power supply:

- Hold the demonstration diode horizontally, and turn it so that the two pins with the greatest distance in the pin base point downwards. - Carefully insert the pin base in the socket of the tube stand until it stops.

additionally recommended:

1 amperemeter 0 ... 30 mA for anode current IA 1 voltmeter 0 ... 300 V für anode voltage UA 1 voltmeter 0 ... 10 V for grid voltage UG 1 voltmeter 0 ... 10 V for heating voltage UF

- Connect the socket F1 of the tube stand to the negative pole and the socket F2 to the positive pole of the 4.5...7.5 V out- put to get a positive heating voltage UF (see diagram). - Connect the socket C of the tube stand to the negative pole and the anode to the positive pole of the 0...500 V output to get a positive anode voltage UA (see diagram). - Connect the socket C of the tube stand to the negative pole and the grid to the positive pole of the 0...50 V output to get a positive grid voltage UG (see diagram).

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4 Characteristics 5 Experiment examples

4.1 Characteristics IA(UA): 5.1 Polarity of the charge carriers (free electrons):

Characteristics IA(UA) for UG = -6 ... 9V, UF = 6.3 V

4.2 Characteristics IA(UG): additionally required: 1 electroscope 540 091 1 high-voltage power supply 10 kV 521 70 or friction rods

- Connect the anode to the electroscope.

a) - The cathode heating being switched off, charge the electro- scope and the anode positively, e.g. with the high voltage U = 2.5 kV or with a friction rod. - Charge the grid positively, e.g. with the high voltage U = 2.5 kV or with a friction rod.

- Switch the cathode heating on (UF = 4.5 V), and observe the quick discharge of the positively charged electroscope.

b)

Characteristics IA(UG) for UA = 0 ... 300 V, UF = 6.3 V - The cathode heating being switched off, charge the electro- scope and the anode positively, e.g. with the high voltage U 4.3 Diode characteristic IA(UG= UA): = 2.5 kV or with a friction rod. - Charge the grid negatively, e.g. with the high voltage U = - 2.5 kV or with a friction rod.

- Switch the cathode heating on (UF = 4.5 V), and observe the constant deflection (or the considerably slower discharge via leakage currents) of the positively charged electroscope.

c) - The cathode heating being switched off, charge the electro- scope and the anode negatively, e.g. with the high voltage U = -2.5 kV or with a friction rod. - Charge the grid positively or negatively.

- Switch the cathode heating on (UF = 4.5 V), and observe the constant deflection (or the considerably slower discharge via leakage currents) of the negatively charged electro- scope.

Characteristic IA(UG = UA) for UF = 4,5 ... 7,5 V (Anode and grid potential are equal.)

Instruction sheet 555 612 Page 4/4

5.2 Amplification of alternating voltages: 5.3 The triode as an oscillator

additionally required: additionally required: 1 measuring resistor 100 kΩ 536 251 1 pair of Helmholtz coils 555 06 1 two-channel oscilloscope e.g. 575 211 1 two-channel oscilloscope e.g. 575 211 1 Function generator S12 522 62 1 STE capacitor 220 pF 578 23 1 transformer 6/12 V 562 73 1 STE capacitor 470 pF 578 24 - Connect the output of the function generator and the 0...50 1 STE capacitor 1 nF 578 25 V output of the DC power supply in series. - Set up the pair of Helmholtz coils so that the coils are - Connect the measuring resistor and the 0...500 V output of aligned in parallel at a distance of approx 5-10 cm and con- the DC power supply in series. nect them according to the diagram.

- Observe and compare the AC components of the grid volt- - Connect the capacitance Cr = 0.22-1 nF in parallel to the age and the anode voltage (with probe 10:1) in the channels anode coil and apply the anode voltage UA = 100-150 V. I and II of the two-channel oscilloscope. - Observe and compare the AC components of the grid volt- - Vary parameters (e.g. UA = 100 V, UG = 0-5 V, U0 = 1 V, age and the anode voltage (with probe 10:1) in the channels arbitrary frequency) I and II of the two-channel oscilloscope. Remark: Here the ground potential is defined by the protective Remark: Here the ground potential is defined by the protective ground of the two-channel oscilloscope. ground of the two-channel oscilloscope.

LD Didactic GmbH . Leyboldstrasse 1 . D-50354 Huerth / Germany . Phone (02233) 604-0 . Fax (02233) 604-222 . e-mail: [email protected]

by LD Didactic GmbH Printed in the Federal Republic of Germany Technical alterations reserved