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 Post subject: Calibrating the EICO 232
PostPosted: Mar Mon 05, 2018 10:30 pm 
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Joined: May Fri 06, 2016 3:41 am
Posts: 333
Location: Johnstown, Ohio
I am attempting to calibrate this meter and I am having some problems. I let the meter warm for the 2 hours specified, used the Zero ADJ. to left zero the dial with the knob set on AC Volts. The next instruction was to have the knob set on AC Volts and the range set to 150V, and then to connect the AC/Ohms probe and the ground clip to the AC source, which in this case was an outlet from my volt bucker set at 117 volts. It further said to use the AC Cal adjust to set the dial to 117 rms (not sure what that is short for). Looked at the scale that I was supposed to use. The only scale for AC readings is the bottom one that goes from zero to 1.5 rms. How do I find a setting of 117 volts AC on that scale. I think I am lost here somewhere. Your thoughts would be appreciated.
Regards,
Don


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 Post subject: Re: Calibrating the EICO 232
PostPosted: Mar Mon 05, 2018 11:12 pm 
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Joined: Feb Wed 07, 2018 6:52 pm
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Location: Stone Mountain, GA
The scale from 0 to 1.5 would also be used for 0 to 15, 0 to 150 and 0-1500V RMS ranges. Just multiply by 10, 100 etc.

RMS = Root Means Squared, an average power of an AC signal. Many meters measure peak voltage and display an appoximate RMS value. Not accurate for distorted or non-sine AC signals.

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 Post subject: Re: Calibrating the EICO 232
PostPosted: Mar Mon 05, 2018 11:28 pm 
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Location: Littleton, MA
SHenion wrote:
The scale from 0 to 1.5 would also be used for 0 to 15, 0 to 150 and 0-1500V RMS ranges. Just multiply by 10, 100 etc.

No, the 1.5 volt scale is just for the AC 1.5 volt range. It's calibrated to compensate for the non-linearities in the diode.

Use the normal DC scales for all the other AC ranges.

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 Post subject: Re: Calibrating the EICO 232
PostPosted: Mar Tue 06, 2018 12:00 am 
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Location: Maryland 20709, USA
SHenion wrote:
RMS = Root Means Squared, an average power of an AC signal. Many meters measure peak voltage and display an approximate RMS value. Not accurate for distorted or non-sine AC signals.

RMS is the value displayed when you measure current (or voltage) with a regular panel meter.

Technically. RMS is the heating value of an AC waveform.
If you apply 10 volts RMS to a non-inductive load (a carbon resistor), its temperature will rise to exactly the same value as it would if you applied 10 volts DC.

The 232 (and 249) measure AC by rectifying it and filtering it, just as you would do in a power supply. The voltage across the filter capacitor is the peak voltage since there is essentially no load on that system.

The meter measures that peak voltage, then displays it on a meter scale that shows its equivalent RMS voltage. That is accurate for a true sinewave and for many other waveforms of similar shape.

This whole exercise came about when televisions became popular. The video signal in a TV set is a complex signal with a known peak-to-peak amplitude. Meters such as the 232 were designed to measure that waveform and display a meaningful value.

Note there are two pairs of scales with the black scales labeled DC-RMS and the red scales labeled P-P, the latter meaning Peak-to-Peak. At any point, the upper and lower voltages are equivalent.

- Leigh

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 Post subject: Re: Calibrating the EICO 232
PostPosted: Mar Tue 06, 2018 1:44 am 
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Joined: May Fri 06, 2016 3:41 am
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Location: Johnstown, Ohio
Thanks Leigh, I alway get a good answer from you and it is always instructive. Can I really just use the DC scales as was stated by another member?

Don


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 Post subject: Re: Calibrating the EICO 232
PostPosted: Mar Tue 06, 2018 1:55 am 
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Location: Maryland 20709, USA
Old Tube wrote:
Can I really just use the DC scales as was stated by another member?
Hi Don,

Yes. the black voltage scales are for both DC and AC RMS voltage.
The red scales are peak-to-peak, which just multiplies the RMS by a fixed factor.

- Leigh

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