A Simple, Valve Curve Plotter

[Nick]

Hi Nick, that sounds a good project. There are things like Lab Jacks that interface (isolated) to a PC and are low cost. They dump data into an XL file and graphs can be plotted directly from that.

It should also be possible to control the Sussex PSUs from a PC to step voltages etc.

If you are going to use a PC to control the voltages of a standard old-school valve tester, then use USB-connected data acquisition and export in to Excel, why not make your life a WHOLE lot simpler, cut out all the middle-man stuff and use a uTracer 3+

The uTracer it almost entirely through-hole (the small surface mount stuff is done for you before you get it) and takes just a few hours to build, all a single Eurocard format (10cm x 16cm) - the kit is very high quality with only top quality components used. The price is set to only cover costs, not to make a profit. It's a labour of love... an active project under continuous development...

The designer, Ronald Dekker, is a professor at Tu Delft & Philips - he has fully documented (in minute detail) every design decision, including failed approaches, complete with detailed explanations. He has a long-standing interest in valves - his website is a goldmine of historical information as he has access to all of Philips' archives.

   

It'll almost certainly cost less, is far far simpler, and way more powerful than any lash-up that you can put together yourself. You'll also learn a ton of stuff building and using it. I can bung a valve into it and have a set of graphs of ACTUAL, not theoretical, behaviour at my chosen operating points in just a few minutes (typically under 5) - over 400 have been built, world-wide

Just some of what it does (there is a whole bunch more, including automatic THD calculation for chosen operating points etc.) - also see What is the uTracer and What can it do?":

• Overview:
  • pulsed measurement of diodes, triodes, pentodes, etc.
    
  • 13 pre-defined measurements:
    
    1. Ia,Is versus Vgrid; stepping Vanode; Vscreen & Vheater constant
       
    2. Ia,Is versus Vgrid; stepping Vanode=Vscreen; Vheater constant
       
    3. Ia,Is versus Vanode; stepping Vgrid; Vscreen & Vheater constant
       
    4. Ia,Is versus Vanode; stepping Vscreen; Vgrid & Vheater constant
       
    5. Ia,Is versus Vanode=Vscreen; stepping Vgrid; Vheater constant
       
    6. Ia,Is versus Vscreen; stepping Vgrid; Vanode & Vheater constant
       
    7. Ia,Is versus Vscreen; stepping Vanode; Vgrid & Vheater constant (positive grid bias mode)
       
    8. Ia,Is versus Vanode; stepping Vscreen; Vgrid & Vheater constant (positive grid bias mode)
       
    9. Ia,Is versus Vheater; stepping Vgrid; Vanode & Vscreen constant
       
    10. Ia,Is versus Vheater; stepping Vanode; Vgrid & Vscreen constant
        
    11. Ia,Is versus Vanode, stepping Vg with Vs = UL(Va,k) simulating ultra-linear operation for pentodes
        
    12. Ia,Is versus Vgrid, stepping Vg with Vs = UL(Va,k) simulating ultra-linear operation for pentodes
        
    13. Ia,Is versus Vanode; stepping Vgrid; Vscreen & Vheater constant; simulating “Schade” feedback
        
  • plot transconductance (Mutual Conductance) as function of bias.
    
  • plot output resistance as function of bias
    
  • continuous measurement of magic eyes
    
  • matching of double-triodes (second anode connected to screen terminal)
    
  • Quick Test feature which measures: Inom, Rp, Gm and mu in a matter of seconds without the need to plot full curves!
    
  • ...
    
• Anode and Screen voltage sources.
  • 2 to 400 V, resolution 0.4 V
    
  • measurement pulse 1 ms.
    
  • nominal output current 200 mA.
    
  • maximum output power 60 W
    
  • hardware current limit 250 mA.
    
  • programmable compliance: 25, 50, 75, 100, 125, 150, 175, 200 mA, response time 20 us.
    
  • short circuit proof.
    
  • linear / logarithmic sweep
    
• Anode and Screen current measurement
  • 0 to 200 mA in 8 ranges with 9.5 bit resolution
    
  • fully auto ranging or manual range selection
    
  • auto averaging or manual average selection
    
  • ranges: 0-1 mA, 0-2 mA, 0-5 mA, 0-10 mA, 0-20 mA, 0-40 mA, 0-100 mA, 0-200 mA.
    
• Grid bias; negative
  • 0 to -50 V, resolution 50 mV
    
  • protected against short circuits
    
  • linear / logarithmic sweep
    
• Grid bias; positive
  • triodes only (screen supply is used source)
    
  • 0 to 200 V
    
  • 0 to 200 mA
    
  • pulsed, so no grid dissipation
    
• Heater
  • 0 to Vsupl (nom. 19.5 V).
    
  • higher voltages with external supply.
    
  • 1.5 A max, limited by fuse.
    
  • direct and indirectly heated cathodes.
    
  • soft start, 0-100% in 10 seconds
    
  • external power supply can be used for higher voltages or low voltage / high current heaters
    
• Data representation
  • On screen graphic presentation with cursor function
    
  • Automatic or manual scaling of axis
    
  • 2 to 25 order polynomial fit though data for extraction of transconductance or output resistance.
    
  • Store graph to file in bmp format
    
  • Store data in table format (several formats possible)
    
  • Storage of all tube specific measurement settings!
    
  • ...