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Hi everyone. I have been busy with lots of things recently, but following my comment on Feathercurl's 'Static Electricity Detector' thread mentioning my electrometer valves I have finally got one in a circuit and I am learning.

I have Russian EM-6 dual tetrode electrometer tubes. Before I purchased, as I normally do, I obtained the relevant datasheet. It was not until somewhat later that I realised how little information there was around on using this type of tube (or maybe just how much there is on more mainstream devices and uses). After quite a bit of searching I did find some very basic information from many sources, but the only specific information often ends at valve voltmeters, which are similar but with less information / issues with input constraints. I did find enough, though, to put something together.

The basic circuit I got to is as shown. The dotted line on the circuit shows the original connection of g2b as in the skeleton circuit I found online. I thought I would try using this tube connection to balance things to zero. It is probably not recommended as the connection is also shown to screen as well and so ideally be grounded, but does appear to work in my “less stringent” application. G1 is connected to a positive potential as these appear to be basically space charge tubes. Originally I was heading a step too far, and using an op amp chip to amplify the output voltage, but ran into problems with it (this is why there is an un-connected pot in the case. I had removed the amplifier, and have now the pot). My original intention meant providing positive and negative supplies as well as 4.5V for the tube heater. I have left the power supply unchanged, but all the -5V does now is to supply the 'zero' pot. That is useful as I have found that I was able to centre the zero point on the pot by minor adjustment of the -5V. I arrived at the circuit component values by educated guesswork and trial and error to home in on the various values given in the data sheet. The material I obtained which gave the skeleton circuit also provided a small amount of information which helped. I have not shown decoupling capacitors, but the lines are decoupled.

To the present time I have only made a few observations rather than anything really specific. The photographs show a test setup with a multi-turn pot in a bridge circuit. This tested principles as I was easily able to balance the bridge and obtain what appeared to be accurate readings for known resistances. The valve itself appears very stable (particularly as compared with normal signal valves).  Although the valve does seem to need a short time to stabilize after any major change, the zero setting does not vary much. Using a cheap meter (checked with my Fluke to the least digit on it), on leaving it switched on with a link across the input for three hours, zero initially set, it was at 1.3mV after an hour and flashing between 1.3 and 1.4mV after a further two hours. The valve itself, in circuit, has little or no gain, as would be expected, but it's very high input impedance appears to more than compensate for this. It may well be likely to have far more resistance to any input stresses, and moderate temperature changes seem to have little effect (less than perhaps with FET's). As it is designed for use with 5V it should well interface with semiconductor circuitry.

My intention is to keep this unit more for test of ideas. My main intention was for use in bridge circuits. I would like to use one of these for the use in the front end of a dedicated unit using perhaps an Arduino with it's analogue ports hence the ability to get data into a PC or other display. As the Arduino is limited to around a millivolt sensitivity at best then use of op-amps may be essential.

If anyone has any circuit information for application of the EM-6 I would find it very useful to see.

Thanks

Tracy
Hi Tracy, for all things valve, you could Google Philips Technical Library. This is a collection of very many volumes in various European languages covering allsorts of different applications. It will be quite a search but I'm sure you will find the data you need.
The Frank Pocknet (DIY audio? www.tubebooks.org?)site has many of these books uploaded as well as lots of other valve stuff.

Ed
Thanks Ed

I was aware of the tubebooks site, and have found quite a bit of information there (particularly of VTVM's). I have not looked directly at the Philips Technical Library, but have a few things that are likely there. One particularly useful article was one from Mullard on electrometer tubes (principly theirs). I think that the main place I am likely to find application information on these Russian tubes is likely only on Russian sites, but it's good to know about the Philips Technical Library.

Tracy
Interesting stuff. Found this - https://www.radiomuseum.org/tubes/tube_eem-6.html - Radiomuseum has a lot of stuff unavailable elsewhere. From this page - http://www2u.biglobe.ne.jp/standard/bdli...list17.htm I found this -http://helpnik.college.ks.ua/cgi-bin/catalog/catalog.cgi?a=0&i=&p=233&f1=&f2=0 A search of " Emanometers type ЭМ-6" throws up quite a few possible sources of info. I had more success with "ЭМ-6" than "EM-6"

It's always a good idea to keep copious notes Tracey, I find I forget easily and try and keep notes of what I've done. Mike Watterson wrote a lot about Russian rod pentodes, I think here and over on the extinct VRAT (Vintage Radio and Television) forum site, there may be something there.

Andy.
Thanks Andy,

ЭМ-6 is likely to be better than em-6 as it is in Russian cyrillic characters. I use both. An issue with using the Russian though is that my Russian is not up to general reading, just some words and technical terms, so when these spam boxes come up on Russian sites I have to be very careful as I don't know what they mean, and you know how insistant they can sometimes be. This makes searching very slow. Some Russian sites are very good though, but they are as general as ours so niche topics are hard to find. I am familiar with Radiomuseum. I learnt much of my early details of Russian rod tubes there. I will have another search though. It is easy to miss a link. Similarly with the VRAT site of which I am also familiar. I have not seen the other sites you mention though. I will have a good look.

I do try to keep notes, and have a folder full of rough notes and circuits. Usually a completed project gets a full writeup (like my Pantry Tx), but I jump here there and everywhere so things do get missed (and when I get to them it takes ages to reverse engineer the circuit LOL). I have a hardback folder in which I keep spec sheets plus key circuits for the Russian valves I have as well as seperate folders with downloaded information for both Russian valves and electrometers in general on my laptop. I tend to be a magpie so have probably got more info than is on any one place elsewhere (at least as far as I have found) on these specific subjects. It's the little things that I know will be somewhere elsewhere though. Like working circuits / schematics, as well as first hand experience using them.

Thanks for the help

Tracy
Hi everyone, I just thought I would give you a bit of information which I have found, which I have not seen elsewhere (although I could be wrong, apologies if so). I am not sure if you are aware of the Russian journal ' Radio'. This did feature two articles on Russian rod tubes, which are translated and presented on the Radiomuseum site (1960 issues 7 and 10). I have found the official site (at least I think it is), which has recent issues on FTP, and one other which has earlier issues (including 1960). I give the links (no guarentees as my Russian is not 100% [and neither is the internet lol]). Well worth a look in the odd issue as they feature many branches of electronics apart from radio. I also find that Russian designers have refreshing other views on electronics. It is obviously the language issue, but worth the effort.

http://www.radio.ru/

http://www.radioman-portal.ru/magazin/radio/

Tracy