How do I determine if an ammeter needs a shunt resistor?

MaxHeadRoom

Joined Jul 18, 2013
30,699
Rather than dismantle the meter, the test outlaid in #9 should tell you.
I don't mind risking purchasing from Amazon, if you don't like it, just send it back, its post paid and they refund the same day.
 

SamR

Joined Mar 19, 2019
5,507
if you don't like it, just send it back, its post paid and they refund the same day.
That is changing and on one of my last purchases I bought some incandescent bulbs but failed to notice they had E17 and not the E25 base that I needed. Couldn't return them... Also, with the increase in China Post shipping cost, Amazon, eBay, and even AliX are all about the same with an edge going to Amazon both in price and shipping speed.
 

Thread Starter

Chris D

Joined Dec 31, 2016
13
Thanks for the additional information everyone, very much appreciated.
Someone asked what I was making - I am making a simple DC multi-meter that can measure current in two ranges and voltage up to 15V. About 20 years ago I built a power supply for my bench that has the same type of gauges and ranges and I like using that over the newer digital power supplies. So, I thought I should make a "multimeter" that looks similar with the analog gauges.
Thanks again everyone.
Chris
 

Audioguru again

Joined Oct 21, 2019
6,826
Many digital multimeters have a analog bargraph on the screen. Mine does.
All my voltage, current and frequency displays are digital. I have not seen an old fashioned mechanical analog meter with a moving pointer for about 50 years.
 

nsaspook

Joined Aug 27, 2009
16,363
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MisterBill2

Joined Jan 23, 2018
27,714
Today the digital gages are cheaper than the mechanical analog versions, and they do sometimes provide better performance. And sometimes not. The old analog ammeter would provide a great deal of useful information to the driver who understood it, while telling the unknowing individual nothing at all. Likewise the analog temperature gage. And an actual mechanical oil pressure gage will tell quite a bit.
But the digital panel looks much nicer and is far cheaper to produce.
Many digital multimeters have a analog bargraph on the screen. Mine does.
All my voltage, current and frequency displays are digital. I have not seen an old fashioned mechanical analog meter with a moving pointer for about 50 years.
I has been several hours since I used my 260 meter to verify a guess.
Frequency is best read on a digital frequency counter, though
 

spar59

Joined Aug 4, 2007
64
Because people still buy them and they can make a profit from it...
I still use mechanical meters as built in indication for some equipment where an accuracy of a few percent is ok as they don't need a separate power supply. Also in my previous job as a protection engineer analogue meters (a good old AVO 7 or 8) were useful for measuring rapidly fluctuating values, the inertia of the pointer would give a rough average whereas a digital meter would just jitter (I accept a high end digital meter could sample and average out such a reading over time), and for doing flick tests to check the polarity of current transformers (meter on CT secondary, battery used to put a pulse of current through the primary) .

However I will add that the cheap analogue meters sold on EBay & Amazon do not in many cases meet their claimed accuracy - to be fair, for the price, I didn't really expect 1.5% and wasn't disappointed in that assumption - full scale could be addressed by tweaks to multipliers and shunts but one had poor linearity and nothing could be done about that, the point is that with a low cost they don't really expect buyers to go through the hassle of a return. However the error is not too huge an issue if you verify the accuracy against an accurate meter and either tweak the meters as I did or even just stick on a label with reading compensation factors but if you actually take on trust that it will be accurate and don't bother testing you could have fun.
 
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