Panel Meter vs Multimeter

Apart from becoming a licensed sparky is there anywhere I can learn HOW to use a Multi meter correctly ?

LOL

Steve

In series to what?
If you are reading the current between the two poles of your solar regulator
without load you read whatever flows depending in the impedance (inner resistance) of your meter. Obviously your panel meters have different impedance than your multimeters, which is quite logical.
good luck
gmd

Hi Steve,

I am not highly experienced with solar panels and regulators but I understand that they are "switching" regulators. In other words, they switch the circuit on and off at a high frequency rather than simply throttling the current. This switching action results in an average current flow and is acceptable to loads such as batteries which are not particularly affected by the switching action.

Panel meters are simple magnetic devices that will respond satisfactorily to the on-off current flow and display the average current although they may exhibit a flickering action if the switching rate is too low.

Digital meters such as your multimeter however work by briefly and repeatedly "sampling" the current then process this value to result in a digital display. When the current is pulsing with the switching action of the regulator, the digital meter sampling rate differs from the regulator switching rate and so "sees" the current at its differing instantaneous values rather than the average value. In other words, it gets all confused.

I would tend to believe the readings of your panel meters rather than the digital meter in this circumstance. Incidentally, the resistances of the two meters will be similar and play no part in this disparity.

Hopefully, someone with practical experience in this area will comment.

Steve,
I would think your using about 100 watt panel and showing roundabout the correct Amperage going TO -> *Regulator* <- FROM panel.

However, because we are not aware where the "spot" is, it's only a guess
I assume the "spot" is between the Regulator and battery?
I assume the battery is fully charged?

therefore; appliances are using ~2 amps which is being replaced by the Solar panel :)

Maîneÿ . . .

What readings do you get when you put the two amp meters in series, reading the same current flow?
If they're still different, then one of them is probably faulty.
Otherwise, a difference in reading when connected between the regulator and the battery may be due to a high internal resistance of one of the meters. The current will be correct, it's just that the meter contributes to the drop in current flow. Many cheap digital multimeters have a 200mV drop across them for full scale current reading, whereas older analogue amp meters will often have much lower voltage drop. This voltage drop will contribute to the different readings in current.
Suggest you take a current reading between the solar panel and the regulator and see if the two meter readings are different. Internal resistance of the amp meters will be less critical on this side.
Gerry

OK - More info required ...
System is a 140 watt Solar panel ( at the time short-circuit Amps 6.22 on the multi meters ) connected to a solar reg the +ve goes to either my multi meter or my panel meter then on to the +ve battery terminal ... -ve is straight connect from reg .. Multi shows 1.8 - 2.4 - then I pull it out of the circuit and replace with panel meter reading is 5.7 A .. Battery is constantly running Waeco on turbo chill mode at -10 C ... ( The Load ) -

Once I get my Clamp Meter things will be better but until then I am baffled ..

Cheers

Steve

Hi guys, not sure if this plays any significant part in this particular instance but I remember someone telling me that an analogue style of meter shouldn't be used to test electronic components because the current draw required for these meters to operate can cause damage to the equipment being tested. Obviously the amp test being done shouldn't damage anything but would the current requirement for the analogue meter be high enough to cause any inaccuracy????
Also Steve do I understand correctly that you were expecting to see more amperage out of the MPPT than the panel is putting in?????

Thanks Pop

Steve,

Everyone else has had their say! Here's my take on it:

Moving coil analogue meters are inherently integrating devices. By their very nature they provide a reading continuously averaged over time. Digital meters also integrate over a short period (typically 0.1 or less of a second), but not continuously. For this reason, a digital meter can give wildly fluctuating readings while monitoring an intermittent voltage or current such as from some switching devices.

It would be worth comparing your meters when they are handling a steady current such as that drawn by a lamp from a battery. If you connect 2 meters in series with each other and monitor a known steady current through them the two readings should be within about 5% of each other. If still wildly different, you have a meter problem. As others have suggested, the resistance of the meters and leads will influence the readings, but should affect the two meters in the same way. (It's not generally realised that when measuring current, a digital multimeter actually measures voltage not current, the voltage developed across a low value precision resistor due to the passage of the current, hence there is always resistance introduced by the meter.)

I think your digital meters are having trouble with the intermittent nature of the current flow from the MPPT controller. I would trust the analogue meter.

One way I've used to get a good average from a digital meter is to fit a low value meter shunt resistor (eg 1/1000 ohm, available from Jaycar and elsewhere) in series with the current to develop a small voltage, feed that voltage though a resistor/capacitor filter to a digital voltmeter. Using the voltage reading, plus Ohms law, will give you a current reading. This way the meter is not exposed to the wild fluctuations present in the original signal.

Suggest try the series connected meters with a steady current to check the meters, then use the analogue one for your present purposes.

HTH

John

"The whole purpose of the exercise was to find an "easy" test to prove an MPPT controller actually puts out more amps than is coming from the solar panel .. "

And that is where you got astray....

MPPT units put out more *power* from the solar panel.

You get maximum power when the panel voltage is well above the battery charging voltage - a standard solar regulator just cuts this extra power off.

You also get power from the solar panel when its output voltage is below the battery charging voltage (as happens in low light conditions) - a standard solar regulator puts out nothing in this situation.

The battery charging current you measure on the MPPT output has a lot to do with the state of charge of your batteries. The input current to the MPPT reflects that too.

If you want to "prove" your test then get two identical analog meters and put one each in series with the input and output of the MPPT. Do your measurements after the battery has powered a load for a while but disconnect the load for the test.
I found digital meters difficult for that, certainly the digital display in my MPPT jumps about a bit on the Amps reading.

Keep in mind to disconnect the panel and the battery while you mess about with amp meter connections

Youtube is your friend . Unless you are a sparky never touch AC .