建立FET電壓表（KP303E，BF245，2N3823）

Update: The refreshed article from elektor electronics magazine, issued 1970 (German language) Cotruction of a FET-voltmeter It gives you a very good undetanding how those circuits work. . This thing is primarily about making a MOSFET voltmeter. The shortest possible description after a proposal given by reader Greg: DIY MOSFET Voltmeter with PCB Design Layout (double sided) uses KP-303E (USSR) or 2N3823 or BF245-247 SiemePhilips Source : article by author Dipl.Phys. Frank Tuengler "Ein univeelles FET-Voltmeter" (A univeal FET-voltmeter) The book: "Elektronisches Jahrbuch 1981", Militärverlag Berlin, GdR Update: Now it gets closer to make something real. I have etched the doublesided pcb. The FET traistor KP303 According to the autho recomendation the FET traistor should have high gain. If you are looking for the KP303 the appendix E should be given. datasheet online:https:rudatasheet.ru/traistokp303/ Now the files section has some files for download, mostly russian language One file has a replacement table in just in case the datasheet website vanishes. Reed Relais (general) It has a contact iide of the tube. The tube has the air evacuated or it is filled with protective gas. Outside sits a coil that agitates the contact iide the tube magnetically. You are on your own finding a suitable reed relais. The contact should be closed normaly (when the coil is not activated). If it has the contacts normally open the default mode seen in the schematics will be reveed. (AC veus DC) The relais of my interest RGK series Amateu rule No.1: take what you have fit! Some GdR made reed relais families varying in mechanical and electrical specs do exist still. I.e. the RGK13 / RGK20 (pin distance) can be found. The RGK20 series has one/two normally open contacts. This does not match n.c. relais contacts as depicted in the schematic. Anyway, I have no problem with reveed AC/DC mode when not activated. Literatur: Online description:http:www.ddr-rft-elektronik.de/relais/rgk-relais-20-1-und-rgk-20-2-relais-mit-schutzrohrkontaktsystem-tgl-32441/ The PDF file has the GdR made "DILIL RGK ReedRelais series" description taken from the former GdR based "Funkamateur" univeal electronics magazin I had started buying and reading 1973. Source: Funkamateur, Heft 2-1988 (abbreviation: FA) The "FA" is now a western owned magazine, exists still. It provides now HAM operato mostly. If they do complain I could find the sources from the manufacturer published in the "radio ferehen electronic" as well. F'*** IP shit (German word: Kacke). The RGK relais do exist still. Can be had on ebay. a few hits below: RGK20 9volt veionhttps:www.ebay.dech/i.html?_from=R40&_trksid=m570.l1313&_nkw=251127931070&_sacat=0 RGK20 12volt veionhttps:www.ebay.de/itm/12V-DDR-REED-RELAIS-RGK-20-1-1-112-01/181855073688 RGK20 18volt veionhttps:www.ebay.dech/i.html?_from=R40&_trksid=m570.l1313&_nkw=230837259141&_sacat=0 Take care on the coil voltage, there do exist many different veio. I will use two 6volt relais in series with a resistor to fit the 20 volt from the psu. The 24volt relais (or 2x12volt in series) is possibly a bit over to much, do not know. Making of the pcb: Trafering to both sides concurrently was a one shot only job. Made a bag from the two sides sheets. Put the copper clad in, fed it through the laminater. Unfortunaly the bag has gotten ripped off by feeding through. But the toner had grip enough to not fall off. Did a number of following passes using freshly cut to size blank baking paper sheets then. If it would work like in laserprinter this could be done by simply feeding the pcb trough. But I wanted not to put risk on the work done before. It worked anyway. Tonertrafer works good enough, helps avoiding using much chemicals or making noise and dust on the cnc mill. The files Some graphics can be read better by selecting the expanded full view. Tick the 45 degree tilted cross overlay in the upper right corner of a picture. Having opened the expanded view there is a line "View Original". Ticking this should bring up the saved file in full size to the screen. Stupid, but if it works for you this way, go with it. Oh my. improved pcb black/white files The ZIP-file has the individual layer files, 1200dpi Some pictures from the book are realy poor to view or even missing. Have made new design files using "Sprint Layout" (Abacom Germany) I'm not about to build the case as shown by the pictures. The MOSFET voltmeter build: This build is not intended to compete with digital voltmete regarding accuracy. You might own a bunch of them. It is about rebuilding a very well made DIY project from the late 70s. Get back the benefit of using analog gauges, perfectly showing trends. It is dead easy to see if a value is iide a specified range. Hard to see from digital multimete. To keep the input impedance high and reduce leakage some industrial grade parts are required. The input selektor should be made from ceramic The mode switch relais should have the contacts perfectly separated when opened. Look for "Reed contact Relais". The name depends on your language a bit. The author gave itructio how to make one DIY. The required power supply can be made using any stable linear voltage regulator with 20volt output. Avoid using switch mode psu. Specs as of the autho build. DC mode Input resistance 10MOhm Linearity deviation less 1% max value error less 2% zero point shift less 0.1% AC mode Input resistance 10MOhm/20pF Linearity deviation (readout is nonlinear) max value error less 2% zero point shift less 0.1% The measuring ranges: AC/DC (AC up to 110kHz) 0.6 Volt 1.2 Volt 3.0 Volt 6.0 Volt 12 Volt 30 Volt Undetand the schematics Feel free to modify the input devider resistor network. The schematics could be simplified if you want DC mode only. Some explanatio on the parts used in the schematics: The KP303 FET-traisto (made in the USSR) can be replaced with western BF245/BF247 or 2N3823. The other traisto are very similar to BC547/BC548 and many other. Germanium diodes could be replaced with low power shottky diodes probably. The univeal switching diode SAY17 (Urevee=50 volts, If= max 175mA, switch delay time =4 nanoseconds) probably has a suitable replacement: Diode 1N4148 (Urevee=100 volts, If= max 200mA , switch delay time =4 nanoseconds) I have no info about the revee current and I will not go into the matter further. Find a data sheet and check it out. If looking for something else take care on leakage current in revee mode. Should be as low as possible. The diodes are grouped in antiparellel series 4 each. This builds the input overload protection. Why not using Z-diodes? Silly question? Z-diodes would reduce the impedance because of leaking current. more to come The PCB The PCB size is 80x50mm fiber glass epoxy material, FR4 recommended I will put the basic itructio regarding some cotruction details and the inital adjustment here later. The chassis/case The input impedance of the circuit is high. Coider using a matall chassis of the same type as used in tube amplifier builds. See the pictures of the completed build made by the author. But details of the mechanical build are hard to see. Hints Take traisto from the same production lot. If you have the tools select the traisto by gain and current. The autho specs are pretty good. But matched pai can improve stability. For best result thermal coupling of the traistor pai seems to be ok. I made a simple build many yea ago uhielded. The meter had the frontplate made from a sheet of aluminium only. It was extremely seitive agait changes of the near field. It moved the pointer in the itrument even by moving my hand toward the meter. Same effect can be seen with radio frequency circuits. Make a good looking representation of your desig and skills ;-) Show off your design work (not limited to pcb desing) even animated in 3D Method 1 making a representation of your design artwork the traditional way, processing pictures in pixelgraphics software only. Have repaired the graphics using the layer mode in Gimp. Pictures of both sides of the pcb loaded into Tinkercad. A screehot makes the picture suitable for presentation purpose. For some details see Method 2 below. Method 2 making a representation of your design artwork using old pictures as template loaded into PCB CAD software and Gimp Scan in the pictures using a good old flatbed scanner or take pictures from digital source Do some postprocessing using free Opeource "Gimp". Cleanup , remove unwanted parts , remove colou, increase the contrast, convert it into 1bit depth black and white picture. Take a picture from a selected layer only in the PCB CAD you are using. Many have an "export layer to picture" function. The green top layer picture comes from the new pcb design. I have made it using "Sprint Layout" made in Germany. It is round about 60 Euro. The beginner friendly software has been pirated in Russia and Asia often. I know. have converted both pictures to 1bit bmp graphics load the pictures as objects into "Tinkercad" stack them up with some clearance set the objects hight to 0.1mm gives a pleasing good result Big benefit of using Tinkercad: -the objects can be displayed easily with several colo and tralucency effect -Tinkercad gives them a light drop shadow. make a screehot to get the final picture. The Tincercad built in "export to picture" does not satisfy my needs. On Tincercad.com a 3D animated visulization of the 3D object you have created can be watched through 3D capable webbrowse. On request the full article can be provided for individual NO COMMERCIAL use only. If it gives you some joy and ipiration, then all is good. Worth the effort. Thats what it is what I'm about. All the time.