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I think you mean "Micronta" which is branding that RadioShack used on a lot of their stuff. And based on the "wheel" you mentioned in your post, it is probably an older analog style multimeter with a needle rather than a digital multimetere (DMM).
You didn't mention the brand or model of the amp you are trying to bias. If you are truly needing to measure current in the 230 milli-ampere range, then setting the meter to it's 500ma scale will be just perfect.
However, when biasing many amps, you are not actually measuring current directly but instead measuring voltage across a resistor. In these cases, you will need to set the meter to a Voltage scale rather than a Current scale.
As for calibrating the meter, don't worry about that. I doubt that you own anything to calibrate the meter against. You can only assume that it is somewhat accurate.
I'm guessing that the "wheel" you talk about is for zeroing the meter needle when measuring resistance (Ohms).... and not applicable when measuring Voltage or Current.
If it were me, I would spend some money on an inexpensive digital multimeter (DMM) but if all you have is an analog meter, that will work.
Thanks for your response. I have a digital meter that only goes up to 200 ma. I am trying to bias AES six pacs. do i need a need a voltage or current scale?
the dial reads 500 m not ma? Also the needle only goes up to 250 DC? not 500?
For the AES/Cary SixPacs you do indeed need to measure current (milliamperes). Cary provides a 1/4 plug and wires that you use to measure the bias current.
The 500m switch position on your meter is most likely 500mA. Analog multimeters have multiple scales for the different measurements. If it is one of the current reading scales (amperes / milliampers) and the switch setting is 500m, then it will work fine.
If you had a decent picture you could post, it would be a lot easier to tell for sure but if I had to make an educated guess, 500m would be it.
Not knowing what your meter looks like, I would also pay attention to where the meter leads plug into your meter. Voltage and Current measurements often have different connector 'sockets' that are used on the meter.
It does have separate plugs. Do I need voltage or meters?
Follow Abe's instructions.
Make sure you have the DMM set properly (A.mA or Vdc) and their leads in the correct slots, or you'll fry the Micronta meter.
If you're not sure of the DMM's orientation, I suggest posting a pic of your meter.
You need to measure millamperes or mA. (Not Voltage)
With the SixPac turned OFF but wired to the speaker......
1) The 1/4" plug needs to be plugged into the SixPac.
2) The meter leads need to be plugged into the Common and the A or mA socket on the meter, and set the meter to the 500mA selection.
3) The meter lead probes need to be attached to the clips/leads from the 1/4" plug from the SixPac.
4) Power up the SixPac and closely monitor the meter. If the needle goes to the left, shut off the SixPac and reverse the leads. If the meter needle starts to rise to the right, monitor it and be sure it doesn't go above about 250mA.
5) Adjust the pot behind the SixPac so the meter reads about 220 - 230mA.
6) Continue to monitor the meter for about 30 minutes and make a final adjustment to 230mA.
7) Shut it all down and disconnect the 1/4" plug.
8) Repeat for the other SixPac amp.
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