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Its Ok to say, the voltage stays the same in parallel providing the Wart can deliver the total current, if the Wart is unable to supply the combined current drawn by the 3 circuits, the voltage will drop.
Its not possible to give a meaningful answer about the current in series question until I know the circuits.
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I am Wanting to be able to power them from one source instead of haveing three cords coming out the back of the case(i am mounting them in one case)
Thanx-
Nick
I am not wanting to measure the same circuit at the same time with the ammeter and the oscilloscope... but just out of curiosity what would happen if I did?
It's difficult to know because we don't have a schematic for each project or what they're measuring.
Suppose you connect the current meter in series with a device drawing 1A and the voltage is 24V with respect to 0V and at the same time you use the 'scope to measure a 5V logic circuit on the same 0V rail. You've unwittingly connected the 24V to the 5V rail in an unknown way so bad things could happen.
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.
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.
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.
I could also think of a dozen or so reasons for not doing certain tests, but I try to restrict my replies to cover the OP's question.
Your reply has too many IF's.
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.
These are 3, off the shelf modules that he wants to power from a single 9V supply.
Even if he connected only the ammeter module in the way you describe it could be damaged, how does that relate to his question regarding the wall wart.
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.
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.!
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.!
How do you know all the probes will be referenced to 0V?
This isn't a signal genrator or 'scope which will definitely have an input/ output referenced to 0V. It's a current meter which can measure both positive and DC currents so will probably have its probes biased at some other vcoltage to obserb the common mode rating of the input amplfier.
I doubt the current probes will be and even if they are it's potentially dangerous trying to measure current on the same circuit as the 'scope's ground is connected to. Suppose one of the probes is 0V (in which case it'd need a negative rail)? Measuring the current through the positive rail would short circuit the supply.
For example, suppose the current meter's amplifier stage looks like the one shown below.
What happens if the current probes are connected to 0V?
It won't work!
Even worse, what happens if the current probes are connected to 9V?
The op-amp is destroyed!
If the circuit being measured is not connected the same ground as the current meter, it doesn't matter because the meter's power supply will float at whatever voltage is required but as soon as you connect the 0V to 0V of the circuit you're measuring bad things can happen.
The problem is, we don't know what the current amplfier looks like so we can't say whether it's safe or not to measure current on the same circuit as the 'scope's ground is connected to. Of course, if it uses something like a hall effect sensor, then it won't be a problem but we haven't seen the schematic so we don't know.
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