Ok..this might seem like spam but it's new to me.
A multimeter with only one button
It's so weird...blank.. They should stick on a second display on.. or something..
Would be crazy if the meter made a giggling sound everytime the power button is turned on. :P
D from BC
The specification says there is 1.7V minimum for AC voltage input. I think the reason is, that otherwise it would be difficult to autodetect that now you want to measure 10 megohm and not the mains power electrical field at your fingertips. Only one more button for switching between volt and resistance and it would be a useful multimeter (because at least I don't need to measure ampere very often).
On a sunny day (Thu, 20 Dec 2007 21:24:31 -0800) it happened D from BC wrote in :
No makes sense, but you will never see this with a current measuring range :-)
The only time(s) I've ever used an actual ammeter have been in tech school, and at this one place where they made battery chargers.
Every other time, I've used a shunt and voltmeter.
Cheers! Rich
On a sunny day (Fri, 21 Dec 2007 18:40:16 GMT) it happened Rich Grise wrote in :
[m]A range so nice to check what your ciruit is doing. Just measuring my PIC sleep consumption for example, yes can be done with a shunt, but a shunt drops voltage. Measure battery charge current. I usually make a test setup before I commit to a peeseebee, and current can be very interesting, even from parts of a circuit. Then there is AC current too, can be nice to see standby current, transformer unloaded, etc. I would not want a meter without Ampere range, never.
(snip)
So does your amp meter. The shunt is just inside the meter.
The old Simpson 260 meters I used as a beginner are actually an ammeter and a current divider.
On a sunny day (Fri, 21 Dec 2007 13:56:37 -0500) it happened John Popelish wrote in :
Yes, obviously, and that is the nice part, you do not have to tangle with different shunts and math, always the right one selected.
The only negative is forgetting to put the meter back on a volt scale, and with some meters, moving the red lead back from the current jack to the volt/ohm jack. I've popped quite a few meter fuses this way. Leaving a current shunt in place allows you to dance over the circuit with a volt meter and make all the checks on one auto range voltage position. No blown fuses. But, obviously from my little pile of blown meter fuses, I use the ammeter ranges quite a bit.
On a sunny day (Fri, 21 Dec 2007 14:09:36 -0500) it happened John Popelish wrote in :
Indeed, I guess we all learned that you do not measure voltage with the test leads in the 10A socket :-) Did it once, and never again. Becomes some sort of a reflex to always put those leads back after measuring current. The cheap meters are now from 10$ up, I have one too, if it ever melts I will just get a new one. But the A range is also nice as, you have only 2 leads to connect, and in some cases live shunts etc can be more dangerous then a couple of fixed test leads. Anyways for big AC currents one should use a current transformer.
button
Meterman do something similar with their new pocket PM5X series:
Dave.
That's why the good high end meters have "input alerts" that beep furiously at you if you have the lead in the AMPS jack and the switch set to voltage. Of course there is nothing stopping you leaving the switch on AMPS and hooking your probes up to a voltage, but most people at least look at the dial before probing.
Dave.
Good Grief! What math? Move the decimal point! 0.1 ohm = 100 mV/A, right?
Then again, I don't have to measure microamp currents to nanoamp resolutions... ;-)
Cheers! Rich
OK, I guess bottom line, all analog meters are current meters. I remember some article about making meter shunts, how to find its internal resistance, and so on. The article went on to say that the simplest way to do this is to make the micro/milli/ammeter into effectively a voltmeter by simply putting a resistor in series with it - this was also an easy calculation: a 0-1 mA meter will read 0-1 volts with a 1K resistor in series with it. A 0-50 uA meter will read 0-1 volts with a 20 K resistor in series with it. These are also called "ohms per volt".
So, anyway, the article said that the simplest way to make an ammeter out of some arbitrary panel meter wasn't to dick around finding its internal resistance and calclating a suitable shunt, but just slap the appropriate restance in series with it, and use it as a voltmeter to measure a shunt that's in series with the current to be tested.
Made a lot of sense to me. :-)
Cheers! Rich
We did that waaaaay back in high school physics class. :-)
Upsets the entity being measured too much.
But you don't readily know what sort of resistance you have just inserted into your circuit (unless up dig up the meter's manual).
An external shunt allows the circuit under test to operate at a single point, so you aren't comparing apples to oranges if you move one meter around for multiple tests.
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