xXAxHillbillyXx
New Member
I have three projects that operate off of 9V I should be able to use one 9V wall wart to power them all if I hook them up in parallel right?
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I have three projects that operate off of 9V I should be able to use one 9V wall wart to power them all if I hook them up in parallel right?
allright Ill give it a look but voltage stays the same in parallel and current stays in series correct
so it is ok if I do not so long as I dont measure the the same circuit with the scope and the ammeter at the same time?
hi,
If your circuit modules have a common 0V [gnd] and a common +Vsupply then you can scope anyone of the modules while they are running.
Connect your scope probe 0V clip to the common 0V line.
I don't know if it's that simple.
Remember we don't know how the current sensor works: is it a sense resistor? Is it a hall effect?
If it's a sense resistor, it might be floating at half the supply because the op-amps used to measure the voltage across it might not be able to operate at or outside the supply voltage, so connecting the current probes to either supply rail might make them non-functional.
EDIT:
Worse still, if the wire carrying the current is at a much higher voltage than the power supply used to power the meter, connecting the 0V of the current measuring circuit to the 0V of the circuit being measured could damage the meter.
Even if they're not connected, the current probe or 'scope shouldn't be used to measure anything at a dangerous voltage because the power supply will float at that voltage.
If your circuit modules have a common 0V [gnd] and a common +Vsupply then you can scope anyone of the modules while they are running.
Sorry, that still doesn't help address my concerns over using the 'scope and current meter simultaneously on the same circuit.
What about the device you are measuring?
If the current meter probes is in series with the positive supply and the negatived is connected to 0V, the common mode range of the internal op-amp might be exceeded, even worse, if the op-amp is powered from an internal 5V regulator it could be damaged.
Sorry, that still doesn't help address my concerns over using the 'scope and current meter simultaneously on the same circuit.
What about the device you are measuring?
If the current meter probes is in series with the positive supply and the negatived is connected to 0V, the common mode range of the internal op-amp might be exceeded, even worse, if the op-amp is powered from an internal 5V regulator it could be damaged.
He wants to run three pieces of test equipment from a wall wart.
It is important for him to be aware that because all of the pieces of equipment are connected to the same power supply their probes will not be isolated from one another. This means that he can not use the pieces of test equipment in the same manner as he would, if the pieces of test equipment were powered from separate power supplies. Ignorance of this might cause him to do something which could damage the equipment or pose an electrical shock hazard.
The 3 modules share a common 0V ground, so the probes from each module are referenced to this 0V, of course he can use his probes from one module to another.
We do this all the time,
Example: a PIC project, a scope, signal generator and power supply all on the same bench using a common 0V on the system.
He is not talking about separate power supplies, you are just causing confusion.!