In my electronics enlightenment journey, I find myself indulging into the fundamentals of understanding the basics of circuits---starting with understanding DMM readings.
I want to make sure I have the fundamentals first before I blow any fuses or circuits from making simple measurements.
Surfing the various threads regarding the Digital Multimeter, I understand that Volts must be measured in paralell with the black lead (com) on the negative and the read lead (Volt 200mA max)
And amps must be measured in series with the actual current running through using blac (com) and red (either 10 ADC 10 amp max unfused or the Volt-ohm 200 mA max fused)
As far as measuring VDC. With the DMM set to 20 DCV, I measured some fairly new batteries (one 9v and 6 1.5volt AA size in series = 9volt)but for both of these the readings showed less than 9v...aprox 8.3 - 8.7 volts. Then I tested an old
9volt battery that couldn't even power the DMM. This gave a reading of a little more than 4 volts. So why do voltages vary. I understand that batteries are depleted of amp/hours, etc., but wasn't aware that it applied to voltage. Can someone put light to these observations...Now, the tricky part... Measuring amps. I haven't yet gotten to the level of measuring individual components, resistors, transistors, diodes, etc. so no need for the related ambiguous jargon just yet . Anyhow, The scales confuse me. On my particular model (YUGO DT-830B)the DCA selection is 200 microamps, 2000 micro amps, 20 miliamps, 200 miliamps, and 10 amps.
Does, 10 amps mean that it's the maximum amps it can read, 200 miliamps is the maximum amperage this selection will take...or??? What if we don't have a clue how much amps a certain load draws, let alone how to read the DMM scales.
For example, I hooked up a 3 volt motor with 2 AA batteries. As I don't have a clue whether a 3 volt motor will draw more than the maximum 200 mA of the one red terminal, I assume it was better to use the 10 amp max unfused red terminal. So the positive terminal from the battery with the red lead, and the black lead in series on to the load (motor).
All kinds of varying readings jumping around. And I'm not sure how to interpret them. With the DMM set to 10A, I get average readings between .09 all the way up to .25 Then with it set to 200 m, the readings are between 1.1 to 2.8.
So how do I interpret these into amps/miliamps? The assumption is that such a small motor can't possibly be drawing 1 or 2 amps, well, I don't really know. That's why I'm posting.
So on top of interpreting the confusing scales of amps, also I would like to know why I can't get a steady still reading of volts or amps with the running motor.
Also, is it possible to measure amp hours of battery cells with the DMM? If so, how must one proceed?
Thanks in advance.
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