#236 

Very nice retro subject.Very well explained, brings back memories 30 years + ago.I really appreciate the slow pace style of your videos.Thanks!

Grateful to have this explained so clearly. Appreciated and thank you

Really helpful and clear explanation! I hope you will continue making videos, you're a great teacher

This and your last video were very well timed for me. I had a meter on a Johnson Viking 2 I am restoring that was not working and I was able troubleshoot it with your info. I enjoy your videos, and look forward to future boat anchors content.

Thanks for the very helpful and illuminating video. I recently picked up a nice old Triplett panel meter for a project. It looked good if a little gunked up, but measured open, and upon disassembly I found that the coiled-up length of ~34AWG magnet wire that they used for the shunt was badly corroded and in several pieces. I needed an excuse to buy some magnet wire anyway and will have a functioning meter soon. Thanks again!

I think your educational videos are most informative videos in electronics on youtube. Im impressed. finaly I found sb whos speaking human language :)

Short video, but very good explanation. Due to a final exam, I didnt see it until now. Please make more videos. I would like small applications from a novice point of view. Again thanks. I look forward to more :)

Really good video with detailed explanation and demonstration!

Excellent video, really easy to understand your explanations.

Looking to use a panel meter on my power supply and this explained everything I needed. Long live Ohms Law !! Thank you very much.

Another useful video, Alan. Thank you.

As always great video explanation and illustration!!! Thank you 73s

Another winner Alan! More fodder for the next solder-melting session.

Alan, Nice video. I needed a shunt and didn't have any nichrome wire, so I used a copper wire and filed down a small area in the center section until I had the full scale reading I needed.

Always an education. Thanks again.

6:04 - If you don't have an accurate low resistance ohm meter you can also get by with a current meter and either another volt meter or the ammeter (panel meter) that you are using. Also keep in mind when you are creating the shunt from multiple resistors that you will also need to confirm that you don't go over the maximum power dissipation of each of the resistors. I would stay under 1/2 the power rating of each for continuous use but for quick tests you could go to the full power rating.

Great video. Super useful.

That was perfect. Thank you. I purchased a digital ammeter to add to a pwr supply I'm building. Going on my experience with automotive ammeters I did not realize a shunt was required. I tied the meter into a simple 5v LED bread board circuit, and released some smoke from my YwRobot P.S. 5V regulator. Now it produces 6.9V. I Went on line to find the specs, before blowing anything else up. I found the exact same unit, and the manufacturer. The device is available in green and blue as well as the red which I have. All of them show shipped with the Shunt included. I'm a little bit perturbed. What happened to the shunt? Clearly the device was repackaged. zip lock bag. 0 to 10 Amps, 5 to 12V is all I'll be using, device I believe goes to 30amp. I know a shunt is made specifically for this thing but I can't find the value, only math classes. I think I can easily figure it out now, even with nothing but multimeter. I see Mr. Caralson was last one to drop by. I spend a lot of time over at his place as well.

Excellent, thanks Alan!

This is great stuff. Thank you.

Simple but beautiful!

Occasionally, when I needed a very low ohm shunt resistor (not having a precision low-ohm meter), I have just calculated how many parallel strands, how long, and of what gauge, of nichrome wire were needed. If you are making a new scale, getting the shunt value close and then measuring the actual deflection for a given Amperage will let you design the final scale. For instance, if you want a 50 Amp meter, making a shunt that gets you close (maybe 53 Amps full scale) will let you make a 50 Amp scale for slightly less than full deflection.

Thanks Al! 73!

brilliant guru

Really cool, thank you

I like this video. Thanks

There hasn't been much said about checking the linearity of these meters, in this or the previous video. It may have been helpful to set the power supply at various intermediate currents, after verifying full scale, to make sure the meter movement is linear and accurate over its full range.

Thanks for sharing. Did you choose that particular analog meter because it was made in New Jersey? Great channel!

Thanks Alan..

Another thing than works well for making a current shunt is some pcb. You can calculate the value pretty closely, then trim it after etching. Of course copper has a much higher temperature coefficient than a real shunt resistor, so it won't be as accurate when it heats up.

Great illustration. Dont you think that a carefully chosen wheatstone bridge 4 arms values has an equivalent benefit or probably adds to this method of separating the applied current leads from the voltage measuring leads (aka 4-wire method)?

Stainless steel works good for making shunts. I have used some 1/8" thick stock.

Thank you for a great explanation. I recently purchased a piece of equipment that has a 500A ammeter. I opened it up and there is a shunt resistor of course for measuring the current, however there is a small potentiometer in series with the leads going to the panel ammeter. So it is exactly like your drawing in #3 but with the addition of a potentiometer in series with the meter. Is the purpose of this to reduce the amount of current actually flowing through the ammeter?

Thanks Alan. I need a better power supply.

Hi Sir, I do have a little question. Do you know if a car fuel gauge in a 90s car is generally an ammeter? If so I can apply the knowledge of your video to test my fuel gauge as well as the sending unit. Thanks for your time!

Very nice video. Maybe you could have mentioned the multimeter series resistance on that caliber and said it was negligible compared to the 10k.

When using a Fluke DVM meter in ammeter mode, is there internal input and output buffers circuits or DC decoupling capacitors on the input ports and output ports while in ammeter mode? There is protection circuits to block DC and buffers even while in ammeter mode.

How would you calculate full scale deflection current given the resistances, the meter current, and the leads between 2 points? No voltage given. This question is from the arco electrician exam book in the back of the book. (Exams)

What lab test equipment can I use to test how much current my AC outlet can handle BEFORE it Pops the mains circuit breaker. If you didn't have or know the buildings wiring or main fuse panel and just wanted to measure how much current each AC outlet can handle what lab test equipment would you use to measure how much current it can handle before popping circuit breakers?

great 4-wire usage, who needs Kelvin clips ?

Adding two resistors (series-parallel or parallel- series) with a little more simple algebra give more flexibility to the uses of any given meter.

Before the 50s they didn't use the resistor Color Code system. Each manufacture on the schematic would indicate a color code system for the resistors and capacitors. What are these other color code systems called and were used before the 50's?

Curious if I would also need a series resistor going to the meter, or is that already contained inside the meter?

Great and much fun as always, but why are they called " analog" meters? Have always wanted to know. Dave W4GSM

Dear Sir, can you explain to me how to change ammeter scale from 50 A to 5 A ?

Alan what size nichrome wire do you suggest to buy

In a DC circuit should the Ammeter or Load be connected to the Positive connector?

Alan, do you have to remove/disable any original internal shunt before doing a mod like this? I have a 0-1A AC ammeter that I want to make dual range (0-10A) with a switchable external shunt. 73 KCØHST

Hi, did you ever do a "four wire" vid please ?

I have one question 2:12 why 0.185 when lab supply shows 2.180v can you please clarify. thanks

Hi, I need some insight on how to make the minor adjustment to get a 50 microamp panel meter extent to work in place of a panel meter specified for 60 microamps. This is for an old Lafayette TE-46 capacitor analyzer. The original meter must have been damaged and someone replaced the original with a 1 Milliamp meter. Using your process The original meter is reading full scale at 1.14 milliamp and a new 50 microamp meter is running full scale at 48 microamps... Thanks for the video as I now know both work and what gets them to full scale.. Note my 100K resistor used for this tests at 9.946k on a 4 wire HP 3478a... That said I'm not sure what to do next. do I pursue working on extending the range of the 50 MA meter or shunting the 1 Milliamp meter? I'd rather use the 50 Microamp meter. Along with this question I've seen some discussion regarding adding diodes across these meters to protect them from going overscale and I'm not sure what or how to add this into the mix... One gentleman added two schottky diodes and another used two 1N4001 diodes reversed against each other. Honestly I don't really understand how these help yet but I'm sure there is a voltage drop issue I need to be aware of...Any insight on how to proceed and certainly some assistance on the shunt values to extend the 50microamp meter would be appreciated... (Would it be possible to use a small resistor in series with the meter instead of a shunt across the meter??) Oh I hope you are still out here... Of all the videos I've seen (and there have been many) yours are the easiest to understand for a novice...

But is the response still fairly linear?

When using Light bulbs as current limiters to test for short circuits its really confusing because if you use one light bulb rated at 60 watts divided by 120VAC = 0.5 amps of current. If you use 2 light bulb wired "in parallel" will be a total of 120 watts divided by 120VAC = 1 amp of current. Logically I would think wiring up resistors in parallel would decrease and lower the current limiting. If you used a 120 ohm/60 watt resistor as a current limiter that is 120ohm /120vac = 1amp of current, if you wire two 120 ohms/60watts that is a total of 60 ohms/120 watts = 0.5amps of current. Its confusing because the light bulbs are inverse of a resistor? or what am I missing and not understanding?

Does any lab current ammeter measure MESH current? because most current ammeter just only measure Branch current. What are the differences are between MESH current and Branch current because you get different current values for MESH current compared to Branch Current. When would an EE engineer or technician want to know and measure the MESH current because most technician are just measuring Branch current?

I'm trying to implement using a digital panel meter without success.

Easier to use a low value resistor (1 Ohm for example) in series with the circuit, then turn the meter into a voltmeter to simply read the voltage drop across the low value resistor. MUCH easier than all those small value resistors. Also, since the meter is multi scale, it is easier to use it as a voltmeter too. Not just dedicate it to reading current.

Your videos are so Succulent ...I never understood why some single cell brain creatures are giving thumbs down to your videos. There are very, very, very, few people like you on YT who give useful info for the mankind. Keep up good the work.

I guess the point here is to do this is thoroughly as you could, but in this case you could safely ignore the Ifs term and just calculate Rs=Vfs/Ifsd. The simplest way to see this is probably that you're doing the calculations to 3 significant digits, (assuming this is a satisfactory amount of precision) whereas 200 µA would only change the 4th significant digit when added to 600 mA. As is to be expected, if the meter is meant to be useful as a voltmeter.

All calculators should use RPN :)

good stuff but isn't a bit too much squeezed in time of 6 minutes ?

Once again an excellent presentation and it ties in so well with the previous meter clip, your Bird meter clips & also with something I've been trying to figure out. Has the shunt in my wattmeter changed value or why would I be getting measurements shown in my clip.ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-S1Ew8wQwSI4.html. My lab equipment is a little more basic...I need to find out voltage required for FSD next I believe for the equation.

All of the panel mount ammeters seem to be from China. 2.5% accuracy. So your calculating the current flowing through the meter the 200 micro amps would be useless. Also the standard for the meters is 75mV. So all of the different models of that ammeter can be made identical. Only the paper with the printed scale would have to be different.

You're not really changing the scale here, are you? The meter's scale is 0.6A, which I think is why you had such a low shunt resistor value, no?

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