Added some HV cable... actually this wire is sold by conrad as test leads. Connector, what is a connector?
- posted
12 years ago
Added some HV cable... actually this wire is sold by conrad as test leads. Connector, what is a connector?
Dude, that's no fun! We want to see dynodes!
;-) Rich
On a sunny day (Sun, 06 Nov 2011 11:27:23 -0800) it happened Rich Grise wrote in :
At least they were clever enough to prefer black over a fancy display of metal.
Added some HV cable... actually this wire is sold by conrad as test leads. Connector, what is a connector?
Got this PMT working with the circuit described in the other thread. With the Na TL crystals I have a huge signal. Am trying to improve a bit on the pre-amp, and as a variation on the PNP darlington, I today tried this; out | | c cathode .... dynodes...... anode b ---- } |------ e | | NPN ///
-1250 V BFR91
No noise! Just signal, That BFR91 is a 5 GHz NPN, and its function here is impedance transformer. The circuit is sensitive to hum on the emitter, no screening in test setup. Added a very small capacitor from emitter to ground to slow it down a bit, and remove some RFI from the HV converter. In the final setup a few cm of screened cable should do the same. Anyways, again, in this circuit, every electron from the PMT is used!
Still experimental, but already more than good enough!
The PMT is a constant current source. You are feeding it into a short circuit. The collector output of the BFR91 is a constant current source.
So you go from a constant current source into a short circuit, then back to a constant current source. What is the purpose for doing that?
Why should that improve things? It seems you should get the same results with a resistor on the output of the PMT instead of the BFR91.
Also, what is the meaning of the -1250V connection near the base? Should that value be placed closer to the cathode?
Mike
Mike wrote:
I did a small LTspice analysis. I don't know your illumination source, but for brief low level pulses, the transistor doesn't turn on fast enough to transfer the PMT output to the load. So if you are looking for fast pulses, this may not be the way to go.
Here's the LTspice files. First is the ASC, then the PLT
Mike
Version 4 SHEET 1 880 680 WIRE 224 160 32 160 WIRE 384 160 224 160 WIRE 32 176 32 160 WIRE 224 176 224 160 WIRE 384 192 384 160 WIRE 32 304 32 256 WIRE 64 304 32 304 WIRE 128 304 64 304 WIRE 384 304 384 272 WIRE 464 304 384 304 WIRE 32 320 32 304 WIRE 128 320 128 304 WIRE 464 320 464 304 WIRE -32 368 -48 368 WIRE -48 384 -48 368 WIRE 32 432 32 416 WIRE 80 432 32 432 WIRE 112 432 80 432 WIRE 384 432 384 304 WIRE 448 432 384 432 WIRE 464 432 448 432 WIRE 32 448 32 432 WIRE 384 448 384 432 WIRE 32 544 32 528 WIRE 384 544 384 528 FLAG 32 544 0 FLAG -48 384 0 FLAG 224 256 0 FLAG 64 304 Q1C FLAG 80 432 Q1E FLAG 384 544 0 FLAG 448 432 R2O FLAG 128 384 0 FLAG 464 384 0 SYMBOL npn -32 320 R0 SYMATTR InstName Q1 SYMATTR Value BFR92 SYMBOL res 16 160 R0 SYMATTR InstName R1 SYMATTR Value 100 SYMBOL voltage 224 160 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL res 368 176 R0 SYMATTR InstName R2 SYMATTR Value 100 SYMBOL current 384 448 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I2 SYMATTR Value PULSE(0 {IS} 0 {IR} {IR} 2n) SYMBOL current 32 448 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I1 SYMATTR Value PULSE(0 {IS} 0 {IR} {IR} 2n) SYMBOL cap 112 320 R0 SYMATTR InstName C1 SYMATTR Value 5pf SYMBOL cap 448 320 R0 SYMATTR InstName C2 SYMATTR Value 5pf TEXT 8 88 Left 2 !.tran 0 10n 0 10p TEXT 0 56 Left 2 ;'Jan Panteltje's PMT Impedance Converter TEXT 344 88 Left 2 !.param IS=4u TEXT 344 112 Left 2 !.param IR=0.5n
[Transient Analysis] { Npanes: 1 { traces: 2 {589828,0,"V(q1c)"} {524291,0,"V(r2o)"} X: ('n',0,0,1e-009,1e-008) Y[0]: (' ',5,4.9996,4e-005,5) Y[1]: (' ',1,1e+308,0.4,-1e+308) Volts: (' ',0,0,5,4.9996,4e-005,5) Log: 0 0 0 GridStyle: 1 } }On a sunny day (Mon, 07 Nov 2011 23:33:25 GMT) it happened Mike wrote in :
Right, you are right. I will play with it some more later.
On a sunny day (Mon, 07 Nov 2011 22:31:24 GMT) it happened Mike wrote in :
This is exactly the point. That eleimites most if not all noise.
Yep And it now goes into the base of my PNP darlington.
Experimenting.
Maybe your newsreader somehow folded the ASCII art?
I suggest you not use tabs, only spaces. I duplicate lines of blanks, then overtype the ascii-art, no distortion in reader's message providing all ines have a leading blank, and all are under 72 chars length ;)
Grant.
On a sunny day (Tue, 08 Nov 2011 22:56:18 +1100) it happened snipped-for-privacy@grrr.id.au wrote in :
There are no tabs in the original posting.
I have deliberately added some threshold, so only the strong signals light the LED:
It is very difficult to capture that from an analog scope trace with a camera, but there are several HUGE pulses, and those light that LED:
This thing is very sensitive to light, so I found a rectangular box normally used for kitchen foil, put the crystal, the PMT and the HV generator in it, the darlington 'preamp' are the 2 transistors next to the scope probe point, that potmeter sets the HV, the no longer used BFR91 with capacitor bottom, the bobbin with wire holds things light-tight:
The preamp will of course go onto the HV board.
I am glad I get such a nice signal out of this PMT, as it is a small one with only 8 dynodes, unlike the other Photonis one I used in first tests that has 10.
As you can see there is a lot of radiation and co[s]mic rays around. Also sensitivity can be set nicely with the HV voltage, this will be controlled by the filtered PWM (AD) from a PIC (at top in picture).
So that was fun, need to order some more of those multimeters though:-)
On a sunny day (Tue, 08 Nov 2011 15:34:27 GMT) it happened Jan Panteltje wrote in :
I wanted it to tick, or be able to tick.
I bought some simple piezo tickers. But these seem (in contrast to their specification) to give only a very faint ticking sound.
So I remembered that a good audible 'tick' sound actually consists of some periods of some frequency, say a few kHz, not just one period. So, and it needs more voltage than 5 V too it seems. So then I decided to try one of those 330 mH inductors have in the box.
+5 +5 | | L 330 mH O|| | | piezo beeper |-------------- 470n c -------||----------- b 5 V C1 | e BC547-B positive pulse 47k | from LED driver | R1 | /// ///Transistor is normally off.
Piezo waveform:
The sound:
Jan Panteltje Inscribed thus:
You could use one of those half inch diameter speakers that they like to use on modems and mainboards. ;-)
-- Best Regards: Baron.
That's as clear as your drawings :-) Sorry, I couldn't stop yself. ikek The ( ) on y keyboard has stopped working
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