Model Boat Mayhem
Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: barryfoote on September 04, 2008, 01:29:14 pm
-
Guys, Some of you....names not be mentioned......put me up to buying one of these little boxes....Well I have done so. The only problem is that do not have a clue how to use them and all the technical gubbins in the instructions, leave me dead. I don't know the difference between AC current and DC Current, just to give you an idea of my ignorance. Now please don't laugh too much at me as there must be others in my position who would benefit from simple and clear destructions :D...sorry I mean instructions...
I Need Help.... :embarrassed: :embarrassed:
Looking at the photo I have worked out that the section marked with a V (top left) is to test volts and indeed when I connect it to a battery I do get a reading that looks like volts i.e 1.5 on a 1.5 battery and 6.1 on a 6 volt battery.... The section top right marked with an A, I assume is for amps, but I do not know where to stick my prongs to get a reading (No rude remarks please)or what setting to use in that section. Help :embarrassed: :embarrassed:
I also assume that the bottom left section measures resistance, but don't know what this means or how to use it. Any help will be gratefully received.
Other questions are:
How do I measure what charge a battery has left in it?
With regards to mains electricity...How do I test whether power exists in a particular cable or not? Using those illuminating screwdrivers is not really an option out here in bright sunlight!!
Now please don't use anything that remotely resembles technical jargon.....Imagine you are talking to the village idiot.......but then again maybe you will be... :D
Cheers guys in advance.
Barry
-
Great Barry, thats the one I've got, now I might find out how to use it. O0
-
Looking at the photo I have worked out that the section marked with a V (top left) is to test volts and indeed when I connect it to a battery I do get a reading that looks like volts i.e 1.5 on a 1.5 battery and 6.1 on a 6 volt battery....
Hey Barry - you're an expert! That's fine for DC volts. With the prongs where they are you can measure the voltage across things: batteries, motors, etc.
The section top right marked with an A, I assume is for amps, but I do not know where to stick my prongs to get a reading (No rude remarks please)or what setting to use in that section. Help :embarrassed: :embarrassed:
Here you need to put the probes in line with things. Between a motor terminal and the wire leading to it, for example, making sure that the multimeter is taking all the current. And in that instance (big amps) imove the red cable to the 10ADC socket and turn the dial to that 10A position. Don't try to measure thirty amps with it!
I also assume that the bottom left section measures resistance, but don't know what this means or how to use it. Any help will be gratefully received.
In the resistance mode stick the red cable back in the V/ohms/mA socket, and measure the resistance of an item by touching the component's terminals with the probe. You could have a couple of minutes of fun by measuring your skin resistance on the highest sensitivity settings! Before the novelty wears off. :D
How do I measure what charge a battery has left in it?
I'm open to others' suggestions on this - but I'd measure a charged battery voltage and a flat battery voltage and determine where on that scale your "unknown" (but same type of) battery voltage is.
With regards to mains electricity...How do I test whether power exists in a particular cable or not? Using those illuminating screwdrivers is not really an option out here in bright sunlight!!
Be very very very careful with mains electricity. :o
The safe way to test it: plug a fused tool or light in that you've tested elsewhere. Do not use meters like this for mains. I know it can (we're all looking at that 500 V AC bit at the top right) but please don't, if you've any concerns about your knowledge.
Regards,
Andy
-
Footski
I've grabbed the pic, and will mark it up a bit and repost it with some Janet-and-John step-by-steps.
In the meantime PLEASE don't go anywhere near mains voltage with it. It will detect and measure mains, but you do need to know what you are doing, and the consequences of getting it wrong could be exciting
It won't btw directly measure what is left in a battery (unless its one of the many Lithium batteries) but it will help in this task - tell us what kind of battery and what its doing ( example 6-cell Nimh drive battery, or 7AH SLA or whatever) and I'm sure lots of experts will pitch in and make it crystal -simple.
andrew
-
Voltage and current connection for a meter:-
http://www.doctronics.co.uk/meter.htm (http://www.doctronics.co.uk/meter.htm)
-
Many thanks for that link, Sandy. It should be mandatory reading for all R/C boat modellers.
FLJ
-
Lesson 2 in the series {-)
http://www.doctronics.co.uk/scope.htm
-
Barry as far as this unit is concerned don't get too wrapped up in resistance at this stage. Suffice to say that resistance is nothing more than that, the resistance to current flow.
I always think of electricity in terms of water in a hose because it is exactly the same.
Voltage is pressure, and is even referred to in that way in some circles. Think of the pressure in the hose pipe as the same as voltage.
Current is the same as flow in the hose. You can have a high voltage (pressure) but a low current (flow) or a low voltage but a high flow and you can even have a high voltage and a high flow but think of them in terms of the hose pipe.
Now add the resistance bit!! Restrict the hose with your fingers and the pressure goes up and the flow goes down. In just the same way increase the resistance and the voltage goes up and the current goes down. You can therefore see that they are all related but for the purposes of what you want you are very unlikely to be measuring specific resistances. You will however find the resistance range usefull for continuity testing. If you measure the resistance between two points in a circuit and you get zero resistance then you know you have electrical continuity between those points. If you get an infinate resistance reading then you know that you have a break in the circuit.
You can use this for testing fuses quickly and easily. If you get zero resistance the fuse is OK but if you get an infinity reading the fuse is blown. Just to familiarise yourself with this range put the probes across a micro switch and flick the switch on and off. You will see the resistance reading vary from zero to infinity.
For the sake of what we do in a model boat just think of DC current. A battery generates DC (direct current) as the current flows around the circuit in the same direction all the time from the positive to the negative terminals on the battery.
AC (alternating current) is found in your mains and flows backwards and forwards at a rate according to the frequency of the circuit, round about 50 times a second, or 50 htz.
In any electrical circuit there is always a relationship between violtage, current and resistance according to V=IR but for the sake of your model boat applications just think of the hose pipe and the volts and current and simplify resistance to either zero or infinity for now.
A couple of things to remember:
Voltage must be measured across a load or supply, i.e. in parallel to the load and current must be measured in line with the load or in series. For a simple motor, switch, fuse and battery circuit the voltage must be measured across the battery terminals (parallel) and current must be measured by disconnecting one of the battery terminals and putting your meter leads one to the battery and one to the disconnected wire (series)
I would set up a small motor with a 1.5 volt battery and a switch and have a play with your meter in varying different ways around this simple circuit. You will soon get the hang of it and find it quite interesting.
Never measure resistance across a live circuit, most modern meters have protection but older ones will go bang and you've lost the meter. Trust me, I've done it!!
Always check the scale is set correctly before you touch the probes to anything. Once again most meters nowadays have protection but putting the meter set at 12 volts across 240 volts would have traditionally been quite entertaining.
When testing resistance or continuity touch the probes together to check they read zero ohms first.
A battery voltage should only be measured when it is under load, measuring a battery voltage across it's two terminals may give you a suitable voltage reading but as soon as you connect it to a load, if the battery is not fully charged the voltage will immediately drop off.
Battery charge is a measure of current not voltage, don't get too wrapped up in volts anyway as you know what it should be by what it says on the cover! You need to know a battery's state of charge however by measuring it's current and you can only measure that when it is discharging to a load.
I hope this all helps a bit. Apologies if it makes things more confusing but if so than ask more questions!
-
Looking at the photo I have worked out that the section marked with a V (top left) is to test volts and indeed when I connect it to a battery I do get a reading that looks like volts i.e 1.5 on a 1.5 battery and 6.1 on a 6 volt battery....
Hey Barry - you're an expert! That's fine for DC volts. With the prongs where they are you can measure the voltage across things: batteries, motors, etc.
The section top right marked with an A, I assume is for amps, but I do not know where to stick my prongs to get a reading (No rude remarks please)or what setting to use in that section. Help :embarrassed: :embarrassed:
Here you need to put the probes in line with things. Between a motor terminal and the wire leading to it, for example, making sure that the multimeter is taking all the current. And in that instance (big amps) imove the red cable to the 10ADC socket and turn the dial to that 10A position. Don't try to measure thirty amps with it!
I also assume that the bottom left section measures resistance, but don't know what this means or how to use it. Any help will be gratefully received.
In the resistance mode stick the red cable back in the V/ohms/mA socket, and measure the resistance of an item by touching the component's terminals with the probe. You could have a couple of minutes of fun by measuring your skin resistance on the highest sensitivity settings! Before the novelty wears off. :D
How do I measure what charge a battery has left in it?
I'm open to others' suggestions on this - but I'd measure a charged battery voltage and a flat battery voltage and determine where on that scale your "unknown" (but same type of) battery voltage is.
With regards to mains electricity...How do I test whether power exists in a particular cable or not? Using those illuminating screwdrivers is not really an option out here in bright sunlight!!
Be very very very careful with mains electricity. :o
The safe way to test it: plug a fused tool or light in that you've tested elsewhere. Do not use meters like this for mains. I know it can (we're all looking at that 500 V AC bit at the top right) but please don't, if you've any concerns about your knowledge.
Regards,
Andy
Andy,
Thanks for that and I will not go near the mains.....Been banned by SWMBO..
Barry
-
Footski
I've grabbed the pic, and will mark it up a bit and repost it with some Janet-and-John step-by-steps.
In the meantime PLEASE don't go anywhere near mains voltage with it. It will detect and measure mains, but you do need to know what you are doing, and the consequences of getting it wrong could be exciting
It won't btw directly measure what is left in a battery (unless its one of the many Lithium batteries) but it will help in this task - tell us what kind of battery and what its doing ( example 6-cell Nimh drive battery, or 7AH SLA or whatever) and I'm sure lots of experts will pitch in and make it crystal -simple.
andrew
Andrew,
Thanks that would be very useful. The batteries I am using are both 6volt 4.6amp lead acid.
-
Thanks for that and I will not go near the mains.....Been banned by SWMBO..
Now you know she REALLY loves you. (or relies upon the cash flow....) ;)
-
Barry as far as this unit is concerned don't get too wrapped up in resistance at this stage. Suffice to say that resistance is nothing more than that, the resistance to current flow.
I always think of electricity in terms of water in a hose because it is exactly the same.
Voltage is pressure, and is even referred to in that way in some circles. Think of the pressure in the hose pipe as the same as voltage.
Current is the same as flow in the hose. You can have a high voltage (pressure) but a low current (flow) or a low voltage but a high flow and you can even have a high voltage and a high flow but think of them in terms of the hose pipe.
Now add the resistance bit!! Restrict the hose with your fingers and the pressure goes up and the flow goes down. In just the same way increase the resistance and the voltage goes up and the current goes down. You can therefore see that they are all related but for the purposes of what you want you are very unlikely to be measuring specific resistances. You will however find the resistance range usefull for continuity testing. If you measure the resistance between two points in a circuit and you get zero resistance then you know you have electrical continuity between those points. If you get an infinate resistance reading then you know that you have a break in the circuit.
You can use this for testing fuses quickly and easily. If you get zero resistance the fuse is OK but if you get an infinity reading the fuse is blown. Just to familiarise yourself with this range put the probes across a micro switch and flick the switch on and off. You will see the resistance reading vary from zero to infinity.
For the sake of what we do in a model boat just think of DC current. A battery generates DC (direct current) as the current flows around the circuit in the same direction all the time from the positive to the negative terminals on the battery.
AC (alternating current) is found in your mains and flows backwards and forwards at a rate according to the frequency of the circuit, round about 50 times a second, or 50 htz.
In any electrical circuit there is always a relationship between violtage, current and resistance according to V=IR but for the sake of your model boat applications just think of the hose pipe and the volts and current and simplify resistance to either zero or infinity for now.
A couple of things to remember:
Voltage must be measured across a load or supply, i.e. in parallel to the load and current must be measured in line with the load or in series. For a simple motor, switch, fuse and battery circuit the voltage must be measured across the battery terminals (parallel) and current must be measured by disconnecting one of the battery terminals and putting your meter leads one to the battery and one to the disconnected wire (series)
I would set up a small motor with a 1.5 volt battery and a switch and have a play with your meter in varying different ways around this simple circuit. You will soon get the hang of it and find it quite interesting.
Never measure resistance across a live circuit, most modern meters have protection but older ones will go bang and you've lost the meter. Trust me, I've done it!!
Always check the scale is set correctly before you touch the probes to anything. Once again most meters nowadays have protection but putting the meter set at 12 volts across 240 volts would have traditionally been quite entertaining.
When testing resistance or continuity touch the probes together to check they read zero ohms first.
A battery voltage should only be measured when it is under load, measuring a battery voltage across it's two terminals may give you a suitable voltage reading but as soon as you connect it to a load, if the battery is not fully charged the voltage will immediately drop off.
Battery charge is a measure of current not voltage, don't get too wrapped up in volts anyway as you know what it should be by what it says on the cover! You need to know a battery's state of charge however by measuring it's current and you can only measure that when it is discharging to a load.
I hope this all helps a bit. Apologies if it makes things more confusing but if so than ask more questions!
Thank you very much for your efforts. it must have taken some time to type all that out and I do appreciate it. I have tested resistance as you suggest. I get a reading of either 000 or 1. I assume 0 is fine and 1 is the infinity you talk about, meaning the circuit is broken?
Now to test the current of say a boats motor. Do I set the dial to say 20m and put the positive prong to the positive of the battery and the negative prong to the negative of the motor, thus getting a reading in amps? Sorry to be a nuisance but I am learning....slowly.
Barry
PS Colin,
If I was brave enough I would ask her which it was!!!!
-
It did and that was my lunchbreak!!
Zero resistance should be a completed circuit, I'm not sure about the 1 as it should read infinity if the circuit is open. Have a look in the book!
For your motor, disconnect the positive wire and connect the positive lead fromm your meter to the positive of the battery and the negative lead from the meter to the cable that you disconnected. Then run the motor and your meter should show the current draw. Obviously in this scenario the motor is not loaded and the current should be low but with this all set up and running put your fingers on the motor shaft and slowly apply pressure. The motor will slow down and the curent will rise on your meter. If in doubt set the current to the highest range and then bring it down until you get a usefull reading.
-
Barry
When measuring the current as Bunkerbarge described, you must also put the positive probe in the (10A) Amp socket on your meter. (Leave it in the normal socket for all other measurements.)
Best wishes
Jules64
-
000 = Zero
1 = the AVO that you are measuring is beyond the scale of the meter, or change to a higher setting.
So if you look at the DC volt range you will see several settings. Best to start at a higher setting and work down. The further down the range the more accurate the reading.
Exactly 1v would read 1.00 or 1.000 etc depending onn the range you are in.
A reading of ' 1' for anything is out of range. This might be your infinity, but it may not.
-
Hey thanks guys, got that bit and will do Bunkerbarges test in tomorrow.....Had a bit too much vino tinto to start with electrics now..
The resistance reading on any setting is either 1 or 000, so I assume on this model that 1 is infinity.
I really appreciate all the effort and hpe Dickyd is also learning from thi!!
Barry
-
Barry, everyone is pitching in for you here... I told you they would and before long you will get the hang of things. A small but important point worth mentioning when measuring current: When you have finished using the current reading facililty on the meter... ALWAYS take the red lead out of the 10Adc socket and put it back into the V,A, ohms socket! If you leave it there and inadvertantly try to read volts.. say your 12v drive battery, it will not like it and will blow the internal fuse rendering the Adc socket inoperable. Should you do this (we all have at some time), you can undo the small screw on the back casing and having prised it off you should find a small glass fuse in there which will have blown. The size of fuse will be stamped on one of the metal end caps so the next trip out will be off to a stockist of 20mm fuses. Buy a pack of five as you WILL do it again some time, there is no shame in this.. it's a fairly common error.
Here's a good test for your boat:
Red lead in 10Adc
Black lead in com
Meter knob set to 10Adc
Remove the red + lead from your boat battery and connect black meter lead to it.
Connect red meter lead to your meter to the + battery terminal.
With boat in bath, slowly open the throttle and watch the reading (in Amps) slowly rise on your meter scale and note how many Amps the boat is drawing from your battery at full throttle.
Now you have a maximum current reading (Amps) which is great but fairly meaningless unless you know what to do next.
Look at your battery, somewhere on it, it will state the voltage and current capacity of the pack. IE '12 Volt 5Ahr'
Now divide the battery capacity (5Ahr) by the max current reading you obtained from your meter.
If for example your meter reading was say.. 2.5Amps then 5Ahr(battery) divided by 2.5Amps (motor reading) equals 0.5. Therefore, at full throttle your boat should theotretically run for 0.5 hrs on a fully charged battery!
You may well say, "I knew that anyway, Iv'e bin running the thing for the past year!" but now at least you have the means to determine how long your boat should run on any given battery.
Another small test whilst the boat is in the bath:
Re-connect red + wire for motor to boat battery as per normal boat running set-up
Place red meter wire back into V,A,ohms socket
Set meter to read 20 Vdc (your battery is lower voltage than that on the scale so the meter will not be overloaded).
Black meter lead to Neg battery terminal.
Red meter lead to Pos battery terminal
Note the battery voltage
Now fire up the boat and go for throttle up with the meter still connected and watch the battery voltage.
You will notice it will fall off very slightly .. even on a fully charged battery.
Give the boat a good caning at full throttle for a few mins and keep an eye on the voltmeter.
If the battery is fully charged and in good nick, the voltage will not be seen to drop very much and will hold up for a considerable period. If the battery is in poor condition or low on charge, the voltage will start dropping quite dramatically.
I hope this helps with the basic idea of using your meter and even if you never bother with the other functions on the front scale, these two functions on their own will tell you most of which you need to know about your boats setup and and running times.
Sorry Barry if it all sounds a bit long winded but it's easier to do than write about.. in fact doing it takes moments when you are familiar with it. Keep us posted on progress.
REMEMBER TO TAKE THE RED LEAD OUT OF THE 10A SOCKET!!
-
Thanks Sheerline.
Let me put it this way. now know more than I did a few hours ago, so that is progress thanks to you chaps. I will give your plan a go tomorrow too. All in the name of science and learning.
Barry
-
Barry, avoid doing it with a hangover!!
Good luck..........Chris
-
Barry,
Just to confirm your assumption, on all the "cheap" Digital Multi-meters I have seen, on the Resistance Ranges 1 is infinity. It is cheaper to display a 1 than try to display the infinity sign, which would probably require a special LCD {-)
Barrie
-
The really nice thing about a digital meter is that when you connect the leads back to front, it still gives a reading, it just puts a "-" in front of the number, rather than doing the needle type meter thing where the needle tries to go the wrong way and crimps itself round the stop.
It helps to remember to switch it off after use (and switch it on before - dont ask) as the battery will last a long time, but its not infinite.
-
Ah, bent needle references Malcolm, do I detect an ex AVO man in that remark? 'Bin there done that' as they say and I was also responsible for filling the scale area with smoke when I was an apprentice!
-
It was an absolutely beautifull huge old Avo meter that I once put across a power supply while it was still set to resistance. It didn't half make me jump :o
The electrical engineer was not a happy teddy!!!
-
The little pop up button designed to protect the meter movement just wasn't fast enough for the likes of us, eh Bunkerbarge!
I have to say that I suddenly discovered that I no longer posess a moving coil multimeter and recently had desperate need of one.
I was working on my re-built Morris Vedette boat engine, trying to sort out the dynamo charging arrangements with the engine running. This engine has a magneto and using a digi meter in close proximity to that unit was as much use as a chocolate firegaurd as the radiated interference drove the digi nuts, with spurious readings all over theplace. The leads act as aerials and pump all sorts of muck into the sensitive measuring circuitry. I found an old Sparkrite dwell meter with a proper moving coil unit and used it as a voltmeter instead. Digi meters are great bits of kit but they can have their own little set of limitations.
-
<Footski> "Wife, wife! Come quick! Look... I finally got the hang of this multi-met....................."
-
PMK, I saw a picture like yours in an ad in yellow pages... it was the electricians logo!
-
Hi, Mr. Sheerline.
Well, that logo ain't I. All I done was googled "electric shock" images and found it right there on the first page.
Reason being is because I don't think anybody told Footski that he won't really get to know and love his DMM until he's had at least a couple hefty belts from two-forty a.c while he's dabbling with the thing.
Bas - if you're earwigging - I don't wish to add more confusion to the issue, but like they said already.... REAL men are using AVOs.
::)
-
No No PMK, don't start him messing with the mains... not yet anyway! You've already got me laughing as I have mental images surging through my brain of past belts I have received whilst working as a tv engineer in the 70s and my reaction to them, two spring to mind:
First, 25kV from the final anode cap of a Philips 25inch colour tv ... the swine didn't wait till I touched it... it just leapt out and got me, threw me up against a wall and as I slid down to the floor, the lady of the house appeared with a cup of tea and said "oh, have you finished already".
Second, whilst making an adjustment to the HT on a very badly designed set which requied one to reach down behind the chassis where the valves (yes valves) faced inward towards the back of the tube. I received a super mains belt which caused my arm to fly out in an upward direction, dragging half the valves with it and showering them around the room.
No matter how self controlled and guarded about foul language in a clients home one is, the slang word for excrement will be heard echoing around the four walls in an instant.
Strangely, I found over the years that I became more tolerant of short sharp mains belts as time went on... you kinda got used to it in a way. Those old sets were badly laid out and difficult to work on without receiving ones weekly dose of mains.
-
So don't all shout at once but who knows (without looking it up!!) where the name Avometer comes from?
-
I became more tolerant of short sharp mains belts as time went on
I used to work with an electrician who would work on 240V lighting circuits live. If he split the neutrals at a lighting fitting he would get a belt if he touched both wires simultaneously, but he could tolerate it without any apparent ill effects.
The poor blighter died of a heart attack eventually... :(
Malc
-
Mercy sakes! What a neat tale YOU tell, Mr. S. Nice one!
TV engineer, eh? See?... I knew all along there was summat suspect about you. I mean, I knew you were an engineer of sorts, but I didn't know you were into servicing tellies.
Now this is really weird, because just 10 mins ago I was outside having a quick puff when the memory of our old TV engineer suddenly popped into my bonce.
And now there's you suddenly telling me that you're also an engineer.
Well in that case, take yourself another 'Respect!'.
I'm curious about that 25Kv leaping at you though. I wish I could sit and have a chin-wag with you. I wanna ask you LOADS of questions.
Are you anywhere near me?
Fancy a pint somewhere?
The most Vs I've ever seen in one day is 415 @ 3-phase.
Blimey, little I did I realise that you HT boys had to actually stick your HAND in there!
I'm in the chair. What you drinking?
(Bring your mate Sweeper along and all).
-
"If he split the neutrals at a lighting fitting he would get a belt if he touched both wires simultaneously, but he could tolerate it without any apparent ill effects."
There is a lot of truth in what you're saying. Maybe the human body gets acclimatised to it or something. Or maybe some folk have a natural hiigher body/skin resistance than others.
When I were a nipper I removed the insulation from a couple bits of wire with my teeth. The other end of the wire was connected to a 13A plugtop... plugged in and switched on. Stripping the neautral was fine, but as soon as I shoved the live in my mouth..... Boooom! SInce then, loads more shocks. I think you just kinda get used to it after a while. I mean, it still stings, but sometime it's just so much easier to work on a circuit when it's live.
I think it's good that at least your mate died of a heart attack, rather than electrocution.
-
<Footski> "Wife, wife! Come quick! Look... I finally got the hang of this multi-met....................."
Brilliant....
Only went out for an evening and missed all this fun...... O0 O0
Having read it all I have packaged up the meter and put it away for a while........My brother is coming out here for a week on Monday so will be busy anyway.....Then with a clear head I am going to start reading the replies through and trying all the Advise given.......I have to learn somehow.
Now....What on earth is an AVO????
Barry
-
but sometime it's just so much easier to work on a circuit when it's live.
Then I wish you a long and happy life - and a shedload of extremely good luck!
(Please guys, DON'T try this at home).
Malc
-
I'm curious about that 25Kv leaping at you though.
Its happened to me as well mate. Back in my "National Service" days I was a Radar Mechanic in the RAF. Instructing a new Mech. one day with the back of the Radar Cabinet open, I said, pointing at a 25Kv power pack, "never touch that". Next thing I knew I was flat on my back two yards away with the rest of the crew laughing their heads off. You dont forget something like that :o
Don B.
-
25KV, hardly worth getting out of bed for!
Now if you want high voltage power supplies try these
http://www.technosinfin.com/hv.html (http://www.technosinfin.com/hv.html)
Live-line working is essential at some points, however when said line has 1600KV on it, then a certain amount of caution is in order. As Welsh_Druid and Sheerline found out, high voltage jumps - at 1600kV it jumps a long way (measure it in meters not inches). Standard first aid kit for an HV lab is a dustpan and brush.
Wombat's 3 rules for high voltage areas
1/. You can't assume that just because it is switched off, it is safe - always go into the test area second
2/. Lightning follows the shortest path - always make sure the person who goes in first is taller than you
3/. Always carry spare underpants
AVO - Amps-Volts-Ohms, became a brand name for multimeters. They are still out there trading as AVO-Megger (another trade name - this time for insulation testers) The classic meters were the AVO 7 and AVO 8
http://www.richardsradios.co.uk/avo7.html (http://www.richardsradios.co.uk/avo7.html)
Wom
-
A lovely toy, but the latest list price of the AVO8 is an eye-watering £935!! Who cares if that includes VAT...........Mrs J would simply NOT countenance my purchasing such a luxury.
Mind, if I keep banging on about an AVOmeter then she might cave in later to something else which I really do want and which costs a lot less..............one needs low cunning with a wife as smart as mine!
FLJ
-
AVO - Amps-Volts-Ohms, became a brand name for multimeters. They are still out there trading as AVO-Megger (another trade name - this time for insulation testers) The classic meters were the AVO 7 and AVO 8
http://www.richardsradios.co.uk/avo7.html (http://www.richardsradios.co.uk/avo7.html)
I have both the AVO 7 & AVO 8, which I tried to sell on Ebay. Unfortunately there were no bids at all. I can see now, with a value of £2 & £10, according to that website, Wombat. The postage alone would have exceeded their costs.
Funny how the value is in the eye of the beholder. ;)
ken
-
AVO's were a rare sight in telephone engineering circles. Just too big and cumbersome. In clockwork, the weapon of choice was a test lamp pluged into a handy battery jack. Getting a bit more technical with yer actural elertonicery, a meter, multi-range 12a, technicians for the use of, was favourite. As sensitive as the AVO, about a tenth the weight and it came in a nice solid pigskin case, essential armour when reading something with it balanced on the top of a rack. Almost all our work was on live gear, as it was either solidly wired in, could only be faulted when in a live working condition, and you couldn't just switch an exchange off. Complaints would arise.
Lethally high voltages were rare outside of the power units, even then they would'nt chase you round the room, but potentially lethal currents were readily available. DC busbars just dont let go until either the battery goes flat or something vaporises.
Being a lineman in a rural area with wartime issue metal poles, reaching through a bed of wires and finding somebody ringing with your ear'ole had its moments.
-
Hi PMK, I'm up here in Norfolk, miles away from you unfortunately. I reckon if we ever had a get together we would probably end up laughing our heads off all night....great!
One of the nastier aspects of e.h.t (extra high voltage) as found in televisions is that it is used to feed the tube (screen) and the lead which carries it is the thick cable with a silicone rubber flat insulator which fits onto the glass at the back. The tube itself is actually like a giant capacitor and even if you disconnect the lead, the tube will hold the charge for a very long time so if you ever had call to disconnect the lead you had to ensure you discharged the tube thoroughly before handling it otherwise.... BLAM!
In my particular case the set was running but the rubber silicone seal obviously had a tiny pihole somewhere and the last thing I saw was a 3inch blue spark which shot out of it and got me. It wasn't the first or the last time this happened but on the other occasions it was only 10kV from the old black and white sets. A hazard which went with the job I'm afraid so we were always aware and very careful but it's the old story, 'familiarity breeds contempt' and sad to say, in some professions where high voltage and high currents are experienced it could prove fatal. I was younger, had a strong heart and like all young men was fearless and contemptable.... oh, and I always wore thick rubber soled shoes in case I got between mains live and earth!
It's probably my fault but you know we have deviated from the digi meter thread here and its probably scaring the life out of Barry if he's reading this lot but perhaps he will stay away from the mains and stick to 12Volts for the time being.
Stay safe chaps........ Chris
-
12 volts.........After reading all this that is a tad too high :o :o :o :o
I have put the thing away for a while till I pluck up the courage to try all your ideas...........maybe next year!!!!
Or........next week O0 O0
-
Perhaps this forum section should be renamed: ' Electrics and all things black out!'
-
"It's probably my fault but you know we have deviated from the digi meter thread here..."
At the risk of sounding like a brown nose, the way you pen your words is dead easy on the eye anyway. It all makes for damn interesting reading, so I don't think Bas will mind the slight deviation. Besides, his bro' is arriving on Monday - he's gonna be too busy with the sangria to even *think* about DMMs for a while.
Norfolk, eh? Nice part of the world. It's not exactly local to my neck of the woods, but who knows?.... maybe Ma Nature might intervene. Twould be good to share a puff, a pint and swap a few lies together. For instance, if ever we did get to rendezvous, the first thing I would ask you is why 6MHz? Why did they stick a 6MHz I.F. in there? It's fascinating. I mean, why that particular number? You know already, radio hams, etc, use their standard 10MHz / 455KHz, etc, itermediate frequencies, right? But why did they decide upon 6MHz for TV?
Naff question?
Yeah, sorry dude. But it's one of those Qs that nobody has ever explained - no reference books have been able to explain, neither.
So once you get past 6MHz, do you then drop down to the more usual 455KHz?... or am I confusing the audio I.F. with that of the visual I.F? (if you see what I'm struggling to ask).
I'll get a couple crates of apple juice sent your way if you don't mind taking time out to teach me something here.
All Rx'ed on what you said about wearing rubber shoes and all. I think we all get the point now. It's just, as Malcolmfrary said, working on a live circuit is sometimes the only option - exceptionally so in your case. My trade is the same as Malc Reade's late mate, so I can understand why he would have been working with live cables sometimes. Besides, the apprentice would normally take an hour just to go isolate the ciircuit, by which time it was quicker to work with it live anyway. It can still give you a tickle, but nowhere near as ropey as the sort of Vs you're playing around with.
Come to think of it, our old TV engineer, he gave me his copy of the Newnes transistor data book when I was around ten, maybe eleven. Funny how this memory should suddenly come home, but his words were along the lines of, "Keep one hand in yer pocket."... even though he never followed his own advice. I mean, he didn't have to, did he? He was the TV man, right? So he obvioulsy KNEW what he was doing. As far as I was concerned he was a God, so he could do whatever he wanted. Not only that - he was the dude that inspired me to buy one of those screwdrivers with a neon in the handle. My old momma went nuts when she the saw me jabbing the thing in the back of our TV. "Get outta there or you'll get yourself all kilt and frazzled!", blah. "Nah, I'll be okay. Watch THIS!....".
That warm glowey neon glow attracted me like a moth to a naked chick's bedside lamp.
When you stop to think about it, that little gun inside the tube, bombarding the screen with all those tiny electrons, scanning the entire screen at the rate of................. HOW many times per second??! Wow!... Now that IS clever.
Same deal with oscilloscopes if you think about it. Compare how they are now to back when the radar boys were first dabbling with those squigly traces on their CRTs.
Which is why I'm wondering why Don B hasn't mentioned sooner that he was a radar operator!
Jeezus Kriced! Where have you blokes been all these years??!
I need to lie down and smoke some medicine now.
I'll be moving to my new house enn-neee day now. Been busy scrubbing, painting, blah, and right now I'm cream-crackered. Not only that, since FLJ said: "she might cave in later to something else which I really do want....", I can't keep meself from wondering what the dude is up to now.
Let's us continue this conversation as soon as I'm in and back online.
Until then, keep your high tensions off her suspensions......................................
-
"Which is why I'm wondering why Don B hasn't mentioned sooner that he was a radar operator!
Hey PMK are you trying to insult me ? {-) A radar OPERATOR ? naw - I wa a radar mechanic complete with lightning flashes on my sleeve. All the operators had to do was watch those green wriggly lines on the screen. WE had to fix things when they went wrong. >>:-(
Mind you they were good blokes. On the night shift, as long as I cooked the supper for all of us, I could go to sleep secure in the knowledge that they would wake me up if anything went wrong, and even start the standby generator before I could get there if the mains failed, and that meant I could have the next day off instead of sleeping and my girl friend could pick me up in the family Rolls-Royce for a day out. Oh - happy days {-)
Why have I never mentioned it before ? - simply because I have forgotten almost everything I learned about radar.
Sorry Folks this is really way off topic !!!
Don B.
-
"Which is why I'm wondering why Don B hasn't mentioned sooner that he was a radar operator!
Hey PMK are you trying to insult me ? {-) A radar OPERATOR ? naw - I wa a radar mechanic complete with lightning flashes on my sleeve. All the operators had to do was watch those green wriggly lines on the screen. WE had to fix things when they went wrong. >>:-(
Mind you they were good blokes. On the night shift, as long as I cooked the supper for all of us, I could go to sleep secure in the knowledge that they would wake me up if anything went wrong, and even start the standby generator before I could get there if the mains failed, and that meant I could have the next day off instead of sleeping and my girl friend could pick me up in the family Rolls-Royce for a day out. Oh - happy days {-)
Why have I never mentioned it before ? - simply because I have forgotten almost everything I learned about radar.
Sorry Folks this is really way off topic !!!
Don B.
Neatishead, Boulmer, Staxton, Buchan, Bishopscourt or Saxaford?
T84, HF200, T85,
I is ...notta 'Scopie!' either!
Rex
-
Hi Rex this is still of topic but I guess were just chatting amongst ourelves till Barry gets back!
Neatishead is just up the road from me and is now a radar museum, we visited it last year and it was very fascinating.
I have to say you are not alone in forgetting much of what you learnt about radar, what I can remember of tv servicing wouldn't fill the back of a fag packet now and given the modern technology in the present day sets, my retained knowledge is absolutely worthless.
Some of my experience does still come in handy from time to time as I did manage to restore the old Austin radio to full working condition a year or so ago and it sits proudly in its own large box under the bonnet of the car, complete with vibrator ht supply humming away. It has one MW band and six short wave bands... we reckon it was probably a bit of surplus wartime kit which was pressed into use for post war domestic vehicles. Lovely old bit of kit and smells great when it has been running for a while and gets heated up.
-
Mind if I ask another question?...
I'm guessing, T's 84 and 85 are probably transmitters, and the 200 is a HF receiver?
Right so far?
And Neatishead, Boulmer, Staxton, etc, are all the places where you were posted.
Am I still on the right track?
Sounds dead interesting.
What were you doing?
Hi, Mr. Druid.
Did I say radio operator? Mate, what's a few thousands volts between sparks. To my mind, part of the fun of reparing 'em is actually using 'em as well. Imagine how it must have been when your Op boys were ogling all them blips... all them tell-tale clues/proof that radio frequency signals actually does bounce off metal.
And imagine how it must have been when you mech' blokes were actually repairing them.
You paint a pretty neat picture, Mr. D.
Why did you have to cook supper?
-
Hi Rex this is still of topic but I guess were just chatting amongst ourelves till Barry gets back!
I will be keeping an eye on things, but will not have much time, so you guys enjoy yourselves....It is very interesting to read....
Right....Off to the airport now....Hasta Lluego,
Barry
-
[
Neatishead, Boulmer, Staxton, Buchan, Bishopscourt or Saxaford?
T84, HF200, T85,
I is ...notta 'Scopie!' either!
Rex
Nope - RAF Barkway - on the highest hill in Hertfordshire.
The monitoring station for the GEE (AMES Type 7000) chain of TXs which transmitted from Daventry (main signal), Stenigot ( nr Louth), Gibbet Hill (Somerset ?), Clee Hill, (Shropshire) - all slave stations to Daventry.
PMK - Supper. As the GEE system was a navigation aid it had to be working round the clock. Our job was to monitor the accuracy of the phasing of the signals otherwise the aircraft got lost !!
So we worked three eight hour shilfts. At night there were four operators plus one mechanic.on duty. There was rarely any work for the Mech. (all the routine maintenance was done by the day shifts) except that if the mains power failed he had to start the standy-by diesel generator (big powerful beasts that took a lot of swinging). We were issued with food ( egg, bacon etc) to cook for our supper and we came to an arrangement that the Mech. would cook for all the shift and then he could go to sleep on a camp bed in his little office, and the Ops. would wake him if needed. Only two Ops were actually working at any time and being good chaps if the mains failed they would try to start the Generator themselves as well as waking the Mech.
Don B.