Correct way to Measure Power Supply Amperage

[Mhz1]

Hello, Just wanted to know a good design (Circuit) to measure DC and AC Amperages without damaging the Power Supply being tested. 

Is there a Particular or certain LOAD to use when measuring the current?

I know you are not suppose to measure direct current from a supply source without a load of some sort, this is why I ask what type of load source to use and the formula to calculate the current reading based on the Load used..

Thanks In Advance for any help here..

 

[prateeksikka]

HI MHz
FOR DEVICE RATINGS!
always connect a moderately high resistance in series with the device and a low resistance ammeter too in series.U should not use too low resistance or a device with low input resistance(this may load your supply)
nor u should connect very high resistance otherwise source wont supply the current at all.So optimal choice is made b/w the too.reply soon about results!

:
prateek

 

[Mhz1]

Thanks for the reply Prat..  Yeah, I have a power supply that appears to be putting out the correct voltage, but I'm uncertain of if the Rated Amperage Output is correct...  It should be delivering 4 amps AC.  But I'm not sure if it is.

The device that it is powering is acting kind of whack at times, and now only a few leds show on it, It won't come on at all now, so I'm not sure if it is the device or the Supply...  By the way the device is a Audio Mixer by Tascam..  Not supported anymore..

Anyhow thanks for the info...

 

[Kevin Weddle]

The correct way depends on the change in current with repect to the changing load. In other words the current waveform that is produced as a result of a changing load. A DC circuit can be simulated with a single resistor, the signals within the system change the DC current. Now that you have the current waveform with respect to time, you can then take the average or even the RMS. If the average is too high or the RMS is too high, you know you have a problem within your system. It may be that you don't have all your signals running properly or you might catch a failure mode.

 

[audioguru2]

I have a power supply that appears to be putting out the correct voltage, but I'm uncertain of if the Rated Amperage Output is correct.

Hi Mhz,
Ohm's Law says that if a power supply is putting out the correct voltage, then it must[/] also be putting out enough current for the load. If it was unable to provide enough current, its voltage would drop.  :

 

[Mhz1]

Thanks Kevin and audioguru, very knowledgable answers with audioguru a bit easier for me to grasp, but none the less a very much thanks to your response Kevin, THANKS.

 

[prateeksikka]

hi audioguru!
all!
when we have voltage fluctuation,some of the devices at our place start making a peculiar sound of vibration just like our refrigerators.I read in a device manual that it happens due to higher current because V*I=POWER =CONSTANT.so when voltage reduces current increases.But isnt it in violation of Ohm's law?
Please explain the fallacy i am in. ???
prateek

 

[audioguru2]

Hi Prattek,
AC syncronous electric motors and switched-mode power supplies use more current when the supply voltage drops as they try to maintain their power output. The motor slips phase which increases the current, and the PWM of the switched-mode power supply increases the "on" time of its power pulses which increases the average current. If the voltage gets too low an AC motor or SMPS might burn-out.