3B SCIENTIFIC® PHYSICS - American 3B Scientific

C5F4F3A1Battery Unit- ++160V AOUT3200 mV!4HERTZ TUBE CONSOLEMAXSET V AMIN340...±1 VOLT OUT 0...±1 VOLT OUTSLOW21 SLOW 2 1 FAST 2 RUNRINGFig. 1 Experiment set-up with the control unit for critical potential tubes7.2.1 Procedure with 3B NETlog TM• At the output V A of the control unit, set theminimum voltage to about 10 V and themaximum voltage to about 35 V, by usingthe 3B NETlog unit to measure thevoltages (smaller by a factor of 1000)between socket 3 and earth and thatbetween socket 4 and earth. Alternatively,the voltages can be set up with the help of amultimeter.• Connect the 3B NETlog unit to thecomputer.• Connect the output “Fast 1” from the controlunit to input A of the 3B NETlog unit andthe output “Fast 2” to input B. (See Fig. 2)• Switch on the 3B NETlog unit and start the3B NETlab program on the computer.• Select the “Measurement lab” function andopen a new data record.• Select analogue inputs A and B and DCvoltage mode (VDC), setting themeasurement ranges to 200 mV for A and2 V for B.• Enter the formula I = -667 * “Input_B“ (unitpA).• Set the following parameters: Measurementinterval = 50 µs, Measurement duration =0.05 s, Mode = Recorder.• Set triggering on the input A with rising edge(20%).• On the DC power supply, set the heatervoltage to 3.5 V.• Start the graph-plotting of the experimentaldata.• Set up the graph with “relative time t in s” onthe x-axis and the quantity I on the y-axis.• Repeat the measurements with slightlyhigher heater voltages and vary theminimum and maximum acceleratingvoltages U A to find the optimum graph.• In the spectrum, identify the 2 3 S peak at19.8 eV and determine its position t 1 on thetime axis.• Identify the ionisation threshold at 24.6 eVand determine its position t 2 on the timeaxis.• Enter a new formula for the quantity Edefined as 19.8 + 4.8 * (t - t 1 )/( t 2 - t 1 ) withthe unit eV; in this expression enter the3